FAR / FSI Calculator
Compute buildable floor area from plot size and zoning—account for setbacks, coverage, height limits, podium/tower splits, bonuses, and parking.
Site / Parcel
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Understanding FAR / FSI: Calculate Development Capacity and Buildable Floor Area
The Floor Area Ratio (FAR) or Floor Space Index (FSI) is one of the most fundamental concepts in urban planning, zoning, and real estate development. At its core, FAR is a simple ratio that links the total built-up floor area of a building (across all floors) to the plot area (the land size). This single number determines how much total floor space you can construct on a given site, shaping everything from building height and density to financial feasibility and housing supply.
For example, a FAR of 2.0 on a 1,000 square meter plot means you can build up to 2,000 square meters of total floor area. You might achieve this as a 2-story building covering the entire plot, a 4-story building covering half the plot, or countless other combinations—FAR controls total volume, not specific building shape. This flexibility makes FAR a powerful yet sometimes confusing regulatory tool used worldwide to manage urban density, control building heights, preserve open space, and balance infrastructure capacity with development intensity.
Our FAR / FSI Calculator helps you explore development capacity scenarios in six flexible modes: (1) Basic FAR/FSI (compute FAR from plot area and desired built-up area, or vice versa), (2) Coverage & Setbacks (account for ground coverage limits and property line setbacks), (3) Height & Floors (translate height limits and floor-to-floor dimensions into maximum floor counts), (4) Podium + Tower (model mixed-use buildings with different FAR for lower podium and upper tower sections), (5) Bonuses & Deductions (add FAR bonuses for affordable housing, green building, or transfer of development rights; subtract exemptions for parking or mechanical space), and (6) Parking & Support (estimate parking area requirements and how they affect net usable floor space). Whether you're a student working on a studio project, a small developer exploring site feasibility, or a planner evaluating density scenarios, this calculator provides instant conceptual estimates to guide your thinking.
Important: This FAR / FSI Calculator is an educational and preliminary planning tool. It does NOT encode the specific zoning regulations, height limits, coverage ratios, parking standards, or approval processes of any particular city or jurisdiction. FAR definitions, bonus structures, and exemptions vary widely—some cities exclude parking and balconies from FAR, others include them; some allow density bonuses for public amenities, others do not. The calculator accepts your user-entered FAR values, setbacks, and assumptions and performs straightforward mathematical computations. Results are conceptual estimates for feasibility exploration, homework assignments, or design brainstorming. For any real development project, always verify local zoning codes, consult a licensed architect or planner, and confirm all assumptions with your planning department before making investment or design decisions.
Use this calculator to build intuition, test "what-if" scenarios, understand how FAR shapes development potential, and learn the fundamental relationships between land area, built volume, and regulatory limits. It's a teaching tool first, a planning aid second—never a substitute for professional expertise or official regulatory guidance.
Understanding the Basics
Plot Area vs Built-up Area
Plot area (also called site area or land area) is the total area of the land parcel you own or are evaluating, typically measured in square feet, square meters, acres, or hectares. This is the footprint of your site as shown on a survey or deed. Built-up area (also called gross floor area, GFA, or total floor area) is the sum of all floor areas in a building that count toward FAR, typically including each storey's floor plate area. If you have a 1,000 m² plot and build a 3-story building with 400 m² per floor, your total built-up area is 3 × 400 = 1,200 m².
It's crucial to understand that ground coverage (building footprint) and total built-up area are different. Ground coverage is the percentage of the plot occupied by the building's base (e.g., 40% coverage on a 1,000 m² plot = 400 m² footprint). Total built-up area is that footprint multiplied by the number of floors. FAR controls total built-up area, not ground coverage—this means you can achieve the same FAR with a tall, slender tower on a small footprint or a short, wide building covering more of the plot.
What Is FAR / FSI?
Floor Area Ratio (FAR) and Floor Space Index (FSI) are two names for the same planning metric, used interchangeably depending on the country or region (FAR is common in the US and parts of Asia; FSI is used in India and some other countries). The definition is straightforward:
FAR = (Total Built-up Floor Area) ÷ (Plot Area)
or equivalently:
Total Built-up Floor Area = FAR × Plot Area
FAR is a dimensionless ratio (both areas must be in the same units). A FAR of 1.0 means the total floor area equals the plot area. A FAR of 2.0 means the total floor area is twice the plot area. A FAR of 0.5 means you can build only half the plot area in total floors. Higher FAR allows more total built space and typically denser, taller buildings; lower FAR restricts development and often results in shorter, more spacious buildings with more open land.
Intuitive Example: Imagine a 1,000 m² plot with a permitted FAR of 2.0. You can build up to 2,000 m² of total floor area. You might build: (a) a 2-story building covering the full 1,000 m² plot (2 floors × 1,000 m² = 2,000 m² GFA), (b) a 4-story building covering 500 m² of the plot (4 floors × 500 m² = 2,000 m² GFA), or (c) a 10-story tower covering 200 m² (10 floors × 200 m² = 2,000 m² GFA). All three scenarios have the same FAR of 2.0, but vastly different building forms, ground coverage, and open space.
Gross vs Net Built-up Area (Conceptual Only)
In practice, what counts as "built-up area" for FAR varies by jurisdiction. Some cities include all enclosed floor area (residential units, commercial space, corridors, lobbies, mechanical rooms, parking). Others exclude certain areas from FAR calculations, such as:
- Parking (above-grade or below-grade): Many codes exempt parking from FAR to encourage developers to provide on-site parking without reducing usable program space.
- Mechanical rooms, elevators, stairs: Some jurisdictions exclude vertical circulation and building systems from FAR.
- Balconies, terraces, or open-air areas: Often partially excluded or counted at a reduced ratio.
- Basements or below-grade space: May be fully or partially exempt.
This calculator uses a simplified "total built-up area" input that you define. If your local code exempts parking, enter your net FAR-countable area (residential + commercial floors only) and leave parking out, or use the Parking & Support mode to model exemptions explicitly. Always check your local zoning ordinance definitions—FAR can mean different things in different places.
FAR Limits and Development Potential
Governments use FAR limits (also called "maximum permitted FAR" or "base FAR") to control urban density and building intensity. A low FAR (e.g., 0.5–1.0) is typical for low-density residential neighborhoods, suburban areas, or conservation zones—encouraging spacious lots, lower buildings, and more open space. A high FAR (e.g., 3.0–15.0+) is common in urban centers, commercial districts, or transit-oriented development zones—allowing dense, tall buildings that maximize land use and support public transit and walkability.
The development potential or buildable capacity of a site is directly determined by:
Maximum Buildable Floor Area = Permitted FAR × Plot Area
This calculator lets you compare "current FAR" (what you have built or are planning) against "permitted FAR" (what the zoning code allows) to see remaining capacity. For example, if you have an existing 1,500 m² building on a 1,000 m² plot (FAR 1.5) and the permitted FAR is 2.5, you conceptually have room to add 1,000 m² more floor area (2.5 × 1,000 - 1,500 = 1,000 m² remaining). This type of gap analysis is valuable for redevelopment studies, extension feasibility, or investment analysis.
Step-by-Step Guide: How to Use This FAR / FSI Calculator
Mode 1 — Basic FAR / FSI
- Enter plot area: Input your site area in your preferred unit (square feet, square meters, acres, hectares). The calculator accepts both rectangular dimensions (length × width) or direct area input if you have an irregular plot.
- Choose FAR or FSI mode: Select "FAR" (common in the US) or "FSI" (common in India)—mathematically they're identical, just different names.
- Input base FAR/FSI value: Enter the permitted FAR/FSI from your zoning code (e.g., 2.0, 1.5, 3.5).
- Click Calculate: The calculator instantly computes the maximum buildable gross floor area (GFA) in square feet and square meters.
- Review results: See total allowable floor area, equivalent floor counts for different footprints, and basic density metrics.
Use this mode for quick "what-if" checks: "If my plot is 5,000 ft² and FAR is 2.0, how much total floor space can I build?" Answer: 10,000 ft² GFA. From there, you can explore how many floors that implies given your desired building footprint.
Mode 2 — Coverage & Setbacks
- Enter plot area and FAR: Same as Basic mode.
- Enter setback distances: Input required setbacks from property lines (front, back, left, right) in feet or meters. The calculator subtracts these from the plot dimensions to find the buildable footprint area.
- Enter maximum ground coverage: Optionally input a coverage ratio (e.g., 60%) if your zoning limits how much of the plot the building can occupy at ground level.
- Click Calculate: The tool computes the net buildable area after setbacks, then shows how many floors are needed to achieve your target FAR within that constrained footprint.
- Review results: See buildable footprint area, required floor count, and total GFA. If the footprint is too small or coverage too low, you'll need more floors—or the FAR may not be achievable within the constraints.
This mode is essential for understanding how setbacks and coverage interact with FAR. A high FAR might seem generous, but if setbacks eat up 40% of your plot and coverage is capped at 50%, you may need a tall, slender tower to hit the permitted FAR—or discover that the FAR is unachievable within height limits.
Mode 3 — Height & Floors
- Enter plot area, FAR, and setbacks: As above.
- Enter maximum height limit: Input the zoning-mandated height limit in feet or meters (e.g., 75 ft, 24 m).
- Enter typical floor-to-floor height: Input the distance between floors (residential: 10–12 ft; commercial: 12–15 ft; parking: 10 ft). The calculator uses this to compute how many floors fit within the height limit.
- Click Calculate: See the maximum number of floors allowed by height, the FAR that could be achieved with full coverage, and whether your target FAR is achievable or blocked by height limits.
- Review results: The tool highlights whether you're "FAR-limited" (hit FAR before height) or "height-limited" (hit height before FAR), guiding design decisions about floor count, floor-to-floor efficiency, and building massing.
Use this mode to answer: "Can I actually build the FAR I'm allowed, or does the height limit force me to stop short?" For example, a FAR of 4.0 on a small plot might theoretically allow a 20-story building, but if the height limit is 60 ft, you can only fit 5–6 floors—making the effective FAR much lower.
Mode 4 — Podium + Tower
- Enter plot area and overall FAR: As above.
- Define podium: Enter the number of podium floors (lower levels, often covering more of the plot) and podium coverage percentage (e.g., 80% for a wide base).
- Define tower: Enter the tower coverage percentage (e.g., 40% for a slender upper tower rising from the podium).
- Click Calculate: The tool computes total GFA split between podium and tower, showing how many tower floors are needed to reach the target FAR given the podium's contribution.
- Review results: See podium GFA, tower GFA, total GFA, and implied tower floor count. This helps visualize mixed-use or high-rise residential designs where a wide podium provides parking, retail, or amenities, and a narrow tower provides residential units above.
Podium-tower configurations are common in urban mixed-use developments. This mode helps you balance the podium's bulk (which provides parking and street presence) with the tower's efficiency (which maximizes views and minimizes core-to-perimeter ratios).
Mode 5 — Bonuses & Deductions
- Enter base FAR: Start with the base permitted FAR from zoning (e.g., 2.0).
- Add bonuses: Input FAR bonuses for affordable housing (inclusionary zoning), green building certifications, transfer of development rights (TDR), or other public amenities. For example, +0.5 FAR for 20% affordable units.
- Subtract deductions: Optionally check exemptions for parking, mechanical space, or balconies. The calculator adjusts net countable FAR accordingly.
- Apply bonus cap: Many codes cap total FAR even with bonuses (e.g., "base FAR 2.0, max with bonuses 3.0"). Enter the maximum allowed FAR to see if bonuses are capped.
- Click Calculate: See total achievable FAR (base + bonuses - deductions, capped at max), total GFA, and a breakdown of bonus sources.
This mode is valuable for developers exploring incentive zoning and understanding how public benefit contributions (affordable housing, public plazas, LEED certification) translate into additional buildable area and project revenue.
Mode 6 — Parking & Support
- Enter plot area and FAR: As above.
- Define use mix: Enter the percentage split between residential, commercial, and office uses (e.g., 70% residential, 30% retail).
- Enable parking estimation: The calculator estimates required parking spaces based on typical ratios (e.g., 1.5 spaces per residential unit, 4 spaces per 1,000 ft² commercial) and computes parking area (assuming 300–350 ft² per space including aisles).
- Click Calculate: See total GFA, parking area, net usable program area (GFA minus parking), and whether parking fits within the buildable envelope or requires below-grade levels.
- Review results: Understand how parking requirements eat into your FAR budget or, if exempt, how much additional structure is needed.
Parking is often the "hidden cost" in FAR-based feasibility. This mode helps you see whether your FAR envelope can accommodate both program space and parking, or if you need structured/underground parking (adding significant cost).
Formulas and Behind-the-Scenes Logic
Core FAR / FSI Formula
At the heart of all FAR / FSI calculations is one simple relationship:
FAR = (Total Built-up Floor Area) ÷ (Plot Area)
Both areas must be in the same units (both ft² or both m²). FAR is dimensionless.
Rearranging to solve for maximum buildable area:
Max GFA = FAR × Plot Area
Example: FAR 2.5 on a 1,000 m² plot → Max GFA = 2.5 × 1,000 = 2,500 m²
Floors, Footprint, and FAR
If your building has a uniform footprint across all floors (like a simple rectangular tower), then:
Total GFA ≈ Footprint Area × Number of Floors
Combining this with the FAR formula:
FAR ≈ (Footprint Area × Floors) ÷ Plot Area
Or: Floors ≈ (FAR × Plot Area) ÷ Footprint Area
This relationship helps you explore trade-offs: a larger footprint (more ground coverage) requires fewer floors to hit your FAR; a smaller footprint (more open space) requires more floors. The calculator uses this logic in Coverage & Setbacks and Height & Floors modes to show how floor count changes with different footprint assumptions.
Setbacks and Buildable Area
Setbacks reduce the usable footprint area. For a rectangular plot:
Buildable Length = Plot Length - (Front Setback + Rear Setback)
Buildable Width = Plot Width - (Left Setback + Right Setback)
Buildable Footprint = Buildable Length × Buildable Width
Height Limits and Floor Count
The maximum number of floors that fit within a height limit is:
Max Floors = ⌊Maximum Height ÷ Floor-to-Floor Height⌋
The floor symbol ⌊ ⌋ means "round down to nearest integer" (you can't build a fraction of a floor).
Bonuses and Deductions
When multiple FAR bonuses are available:
Total FAR = Base FAR + Σ(Bonuses) - Σ(Deductions)
Total FAR = min(Calculated FAR, Maximum Allowed FAR)
Most codes cap total FAR even with bonuses (e.g., "no more than 3.0 regardless of bonuses").
Worked Example 1 — Basic FAR Calculation
Scenario:
- Plot area: 500 m²
- Permitted FAR: 2.0
- Question: What is the maximum total floor area I can build?
Solution:
Max GFA = FAR × Plot Area
Max GFA = 2.0 × 500 m²
Max GFA = 1,000 m²
Interpretation:
You can build up to 1,000 m² of total floor area across all floors. Possible configurations:
- Option A: 2 floors covering full 500 m² plot (2 × 500 = 1,000 m² GFA)
- Option B: 4 floors covering 250 m² footprint (4 × 250 = 1,000 m² GFA)
- Option C: 5 floors covering 200 m² footprint (5 × 200 = 1,000 m² GFA)
All achieve FAR 2.0, but have different building heights, ground coverage, and open space.
Worked Example 2 — FAR with Setbacks and Height Limit
Scenario:
- Plot: 100 ft × 150 ft = 15,000 ft² gross area
- Setbacks: 20 ft front, 15 ft rear, 10 ft each side
- Permitted FAR: 3.0
- Maximum height: 75 ft
- Residential floor-to-floor: 10 ft
- Question: How many floors can I build, and what is the total GFA?
Step 1: Calculate buildable footprint after setbacks
Buildable Length = 150 ft - (20 ft + 15 ft) = 115 ft
Buildable Width = 100 ft - (10 ft + 10 ft) = 80 ft
Buildable Footprint = 115 ft × 80 ft = 9,200 ft²
Step 2: Calculate max GFA from FAR
Max GFA = FAR × Plot Area
Max GFA = 3.0 × 15,000 ft²
Max GFA = 45,000 ft²
Step 3: Calculate max floors from height limit
Max Floors = ⌊75 ft ÷ 10 ft/floor⌋
Max Floors = 7 floors
Step 4: Check if FAR is achievable
Max GFA with 7 floors over full footprint = 7 × 9,200 ft²
Max achievable GFA = 64,400 ft²
Interpretation:
The height limit allows 7 floors, and the buildable footprint is 9,200 ft². If you build 7 floors over the full footprint, you get 64,400 ft² GFA. However, the FAR limit is 45,000 ft². Therefore, you are FAR-limited, not height-limited.
To stay within FAR 3.0, you need:
Required Floors = ⌈45,000 ft² ÷ 9,200 ft²⌉
Required Floors ≈ 5 floors (4.9 rounds to 5)
Final Answer: Build a 5-story building covering the full buildable footprint (9,200 ft²), yielding 5 × 9,200 = 46,000 ft² GFA, slightly over FAR 3.0. You'd need to reduce coverage slightly or use 5 floors at reduced footprint to hit exactly 45,000 ft². The 75 ft height limit accommodates 7 floors, but FAR caps you at 5 floors of full coverage.
Practical Use Cases
1. Owner Checking Existing Building FAR
A property owner has a 3-story apartment building on a 10,000 ft² lot. Each floor is about 6,000 ft², so total GFA is 18,000 ft². They want to know their current FAR to see if they have room to add more units or floors. They enter plot area 10,000 ft² and built-up area 18,000 ft² in Basic mode. The calculator shows FAR = 1.8. If the zoning allows FAR 2.5, they conceptually have room for an additional 7,000 ft² (2.5 × 10,000 - 18,000 = 7,000 ft²), potentially enough for one more floor or a small addition. This quick check helps them decide whether to explore a redevelopment feasibility study.
2. Developer Sketching Feasibility for a New Mixed-Use Building
A small developer acquired a 1,500 m² urban lot zoned for FAR 4.0. They want to understand how much total floor area they can build to estimate unit count and project revenue. They use Basic FAR mode: 1,500 m² × 4.0 = 6,000 m² total GFA. Assuming residential units average 80 m² each, that's roughly 75 units. They then switch to Coverage & Setbacks mode, input 5 m setbacks all around, and see the buildable footprint drops to about 1,200 m². With a 60% coverage cap, footprint is 720 m². To reach 6,000 m² GFA, they need 6,000 ÷ 720 ≈ 8–9 floors. They check Height & Floors mode with a 30 m height limit and 3.5 m floor-to-floor: 30 ÷ 3.5 ≈ 8 floors max. Conclusion: the FAR is achievable within height limits, and the project is conceptually feasible. They proceed to detailed design and financial modeling.
3. Architecture Student Exploring Studio Massing Options
An architecture student is assigned a studio project: design a residential tower on a 40 m × 50 m site (2,000 m²) with FAR 3.5. They need to explore different massing strategies. They use the calculator to test scenarios: (A) Low-rise, high coverage: 5 floors × 80% coverage (1,600 m² footprint) = 8,000 m² GFA (FAR 4.0)—exceeds limit. (B) Mid-rise, medium coverage: 7 floors × 60% coverage (1,200 m²) = 8,400 m² GFA—still too much. (C) High-rise, low coverage: 10 floors × 35% coverage (700 m²) = 7,000 m² GFA (FAR 3.5)—perfect! The calculator helps them quickly find that a slender, 10-story tower on 35% of the site hits the FAR target, leaving 65% open for landscaping and amenities. This informs their concept diagrams and massing models.
4. Investor Comparing Two Sites in Different Zones
An investor is choosing between two land parcels: Site A is 8,000 ft² in a zone with FAR 2.0; Site B is 6,000 ft² in a zone with FAR 3.5. They want to know which offers more total buildable area (and thus more potential revenue). Using the calculator: Site A: 8,000 × 2.0 = 16,000 ft² GFA. Site B: 6,000 × 3.5 = 21,000 ft² GFA. Site B, despite being smaller, offers 31% more buildable floor area due to higher FAR. If construction costs and land prices are similar, Site B may be the better investment. The calculator provides a quick, apples-to-apples comparison of development capacity.
5. Planning Commission Exploring Upzoning Scenarios
A city planning commission is considering increasing FAR from 1.5 to 2.5 in a transit-oriented development (TOD) zone to encourage more housing near a new subway station. They want to understand the impact on buildable capacity. They use the calculator on a typical 5,000 m² parcel: current FAR 1.5 = 7,500 m² GFA; proposed FAR 2.5 = 12,500 m² GFA—a 67% increase in buildable floor area. Assuming 100 m² per apartment, that's a jump from 75 units to 125 units per parcel, a gain of 50 units. Across 20 parcels in the zone, that's 1,000 additional housing units. The calculator helps quantify the housing supply and density impacts of the proposed zoning change, informing public hearings and policy decisions.
6. Developer Testing Affordable Housing Bonus Feasibility
A developer is considering an inclusionary zoning bonus: if they provide 15% of units as affordable, they get a +0.5 FAR bonus (base FAR 3.0 → 3.5 with bonus, capped at 4.0). They use Bonuses & Deductions mode: base FAR 3.0, inclusionary bonus +0.5, max cap 4.0. On a 2,500 m² site, base GFA = 7,500 m²; with bonus, GFA = 8,750 m². The extra 1,250 m² (about 15 market-rate units at 80 m² each) could generate $3–5M in additional revenue, more than offsetting the cost of providing affordable units. The calculator helps them quickly see whether the bonus is financially attractive and whether it's capped (in this case, it's not—total FAR 3.5 is below the 4.0 cap). This informs their pro forma and decision to pursue the inclusionary bonus.
7. Architect Balancing Parking Requirements with Residential GFA
An architect is designing a 50-unit residential building on a 1,000 m² site with FAR 3.0 (3,000 m² total GFA). Zoning requires 1.5 parking spaces per unit (75 spaces total). At 30 m² per space (including aisles), parking requires 2,250 m². If parking is excluded from FAR, the architect has 3,000 m² for residential units plus 2,250 m² for parking (5,250 m² total building). If parking counts toward FAR, only 750 m² remains for residential (3,000 - 2,250 = 750 m²)—clearly infeasible. They use Parking & Support mode to model both scenarios and confirm that parking exemption is critical for project viability. This informs their discussions with the planning department and decision to provide below-grade parking (typically exempt) rather than above-grade (often counted).
8. Real Estate Course Student Analyzing Density and Urban Form
A real estate economics student is writing a paper on how FAR shapes urban form. They use the calculator to model three neighborhoods: (A) Suburban (FAR 0.5, low-density single-family homes), (B) Urban Residential (FAR 2.0, mid-rise apartments), and (C) Downtown High-Rise (FAR 8.0, skyscrapers). For a standard 10,000 m² city block, they compute buildable GFA: (A) 5,000 m² (about 50 single-family homes at 100 m² each), (B) 20,000 m² (about 200 apartments at 100 m² each), (C) 80,000 m² (about 800 apartments). The calculator visually demonstrates how FAR drives density, housing supply, and the need for transit and infrastructure. The student includes these scenarios in their paper to illustrate the relationship between zoning policy and urban development patterns.
Common Mistakes to Avoid
1. Mixing Up Area Units
Entering plot area in square meters and built-up area in square feet (or vice versa) without converting will produce meaningless FAR values. Always use the same unit system for both areas, or use the calculator's unit selector to ensure consistent conversions. For example, FAR = 10,000 ft² ÷ 500 m² is nonsense; convert both to the same unit first.
2. Ignoring Local Definitions of "Built-up Area"
Assuming all floor area counts equally toward FAR without checking your local code. Some jurisdictions exclude parking, basements, mechanical rooms, balconies, or below-grade space. Others include everything. Using the wrong definition can lead to FAR calculations that are off by 20–40%. Always verify what your zoning code counts as "gross floor area" or "built-up area" before running scenarios.
3. Treating FAR as the Only Constraint
Focusing solely on FAR and forgetting that height limits, setbacks, coverage ratios, parking requirements, shadow studies, fire codes, and structural feasibility can be just as restrictive—or more so. A generous FAR of 5.0 is useless if the height limit only allows 3 floors and coverage is capped at 40%, making the effective achievable FAR far lower. Always consider FAR in the context of the full regulatory and design envelope.
4. Over-Interpreting Conceptual Scenarios as Approvals
Reading a simple FAR-based calculation from this tool as a guarantee that your building design will be approved. FAR is just one metric; real projects require detailed architectural plans, structural engineering, environmental reviews, public hearings, and design review board approval. A conceptual "FAR 3.0 on 2,000 m² = 6,000 m² GFA" is a starting point for discussion, not an approved building permit.
5. Forgetting Circulation, Common Areas, and Building Efficiency
Planning a program using gross floor area (GFA) without allowing for corridors, lobbies, elevator shafts, mechanical rooms, and structural walls. Typical building efficiency (net usable area ÷ GFA) is 75–85% for residential, 80–90% for office. If your FAR gives you 10,000 m² GFA, you might have only 8,000–8,500 m² of net usable space for apartments or offices. Account for circulation and core area when estimating unit counts or revenue.
6. Confusing FAR with Ground Coverage
Thinking that FAR 1.0 means "you can cover the entire plot with one floor." FAR controls total floor area, not footprint. FAR 1.0 could be 100% coverage at 1 floor, 50% coverage at 2 floors, 25% coverage at 4 floors, etc. Ground coverage (lot coverage ratio) is a separate zoning metric. A site might have FAR 3.0 but only 40% coverage, forcing a taller, slender building.
7. Not Checking Whether Bonuses Are Cumulative or Capped
Assuming you can stack unlimited FAR bonuses (affordable housing +0.5, green building +0.3, TDR +0.7 = +1.5 total) without verifying the zoning code's maximum allowed FAR cap. Most codes say "base FAR 2.0, max with bonuses 3.0," meaning you can only get +1.0 total, not the full +1.5. Misunderstanding bonus caps can lead to overly optimistic financial projections.
8. Using Unrealistic Floor-to-Floor Heights
Entering an 8 ft floor-to-floor height to squeeze more floors into a height limit, when structural depth, ductwork, and code minimums require at least 10–12 ft for residential or 12–15 ft for commercial. Unrealistic floor heights produce floor counts that can't be built, wasting design time and leading to disappointment when structural engineers or contractors correct the assumption.
9. Ignoring Setback Impacts on Small Lots
On small urban lots (e.g., 30 ft × 100 ft), generous setbacks (15 ft front, 10 ft rear, 5 ft sides) can consume 50%+ of the plot, leaving a tiny buildable footprint. A high FAR becomes unachievable because you'd need an impossibly tall, narrow tower. Always model setbacks explicitly on constrained sites to see if the FAR is physically realizable.
10. Forgetting Podium-Tower FAR Distribution
In podium-tower designs, assuming the entire FAR can be distributed however you like without checking whether codes require separate FAR limits for podium and tower, or whether podium coverage affects tower setbacks. Some codes mandate "tower must be set back X feet from podium edge" or "podium FAR max 1.5, tower FAR max 5.0." Misunderstanding these rules can invalidate your massing concept. Use the Podium + Tower mode carefully and verify code requirements.
Advanced Tips and Strategies
1. Test Multiple FAR Scenarios to Understand Upzoning Potential
Don't just model the current permitted FAR—test +0.5, +1.0, +2.0 increments to see how much additional buildable area (and project value) an upzoning could unlock. For example, if current FAR is 2.0 and you test FAR 3.0, you might find an extra 30–50% GFA, translating to millions in additional revenue. This analysis is valuable for advocacy, rezoning applications, or long-term land banking strategies.
2. Balance Height, Footprint, and Open Space for Best Urban Form
The same FAR can yield vastly different building forms: a squat, wide building with little open space vs a tall, slender tower with generous landscaping. Use the calculator to explore how different footprint/floor combinations affect urban design quality, views, daylight, and outdoor amenity. Often, a taller, more slender building (e.g., 40% coverage, 8 floors) creates better space and place quality than a low, bulky building (e.g., 80% coverage, 4 floors) with the same FAR.
3. Integrate FAR Analysis with Financial Pro Formas
Once you know your buildable GFA from FAR, link it to construction costs ($/ft² or $/m²), sale prices or rents, and financing terms to compute net present value (NPV), internal rate of return (IRR), or profit margin. For example, 50,000 ft² GFA at $300/ft² revenue and $200/ft² cost = $5M profit before land and soft costs. Use this to compare sites, justify land prices, or decide whether to pursue FAR bonuses (is the extra GFA worth the cost of providing affordable units or public plazas?).
4. Model Phased Development Scenarios
If you have a large site, you might develop in phases: Phase 1 uses 50% of allowed FAR, Phase 2 uses the rest 5 years later. Use the calculator to see how much GFA each phase can have, and whether market absorption, financing, or infrastructure capacity supports phasing. This is especially useful for master-planned communities or campuses where infrastructure (roads, utilities) is built incrementally.
5. Use FAR to Communicate Density Concepts to Non-Experts
FAR is a simple, intuitive number that non-planners can understand more easily than "dwelling units per acre" or "floor space index." When presenting to community boards, investors, or elected officials, lead with FAR: "Current zoning allows FAR 1.5, proposed is 2.5—that's a 67% increase in building size." Pair it with simple diagrams from the calculator (footprint × floors) to make density tangible and understandable.
6. Check Whether Transferable Development Rights (TDR) Are Available
In some cities, you can purchase unused FAR from neighboring properties (e.g., a landmarked building that can't be developed) and "transfer" it to your site, increasing your allowed FAR. Use the Bonuses & Deductions mode to model TDR scenarios: base FAR 3.0 + TDR 1.0 = 4.0 total. Evaluate whether the cost of purchasing TDR rights (often $/ft² of transferred FAR) is justified by the additional revenue from extra GFA.
7. Explore Mechanical Penthouse and Rooftop Exemptions
Many codes exempt mechanical penthouses, elevator overruns, and rooftop equipment from FAR and height limits (provided they meet certain setback and screening requirements). Use Bonuses & Deductions mode to model exemptions: if your mechanical/circulation space is 10% of GFA and it's exempt, you can add it "for free" without consuming FAR. This can be a significant design and cost advantage, especially on constrained sites.
8. Account for Floor-to-Floor Efficiency in Early Massing
Shorter floor-to-floor heights allow more floors within a height limit, but may compromise structural efficiency, duct routing, or ceiling height quality. Test realistic F2F values (residential: 10–11 ft minimum; commercial: 13–15 ft for large spans and MEP). Shaving 1 ft per floor might gain 1 extra floor but result in unmarketable spaces or higher construction costs. Use the Height & Floors mode to find the optimal balance.
9. Use Podium-Tower Configurations to Maximize FAR on Constrained Sites
On sites with challenging setbacks or coverage limits, a podium-tower design can help you hit high FAR: wide podium (60–80% coverage, 3–5 floors) provides parking, retail, and amenity space; slender tower (30–40% coverage, 10–20 floors) provides residential or office space. The calculator's Podium + Tower mode lets you optimize this split to maximize GFA while respecting coverage, setback, and height rules. This strategy is common in urban mixed-use and high-rise residential projects.
10. Benchmark Your FAR Against Comparable Projects
Research FAR values for similar projects in your market (check planning department records, architectural publications, or CoStar data). If your FAR is significantly higher or lower than comparable buildings, investigate why: different zoning district, bonuses utilized, older regulations, or errors in your assumptions. Benchmarking helps you reality-check your scenarios and identify opportunities (underutilized FAR) or risks (overly aggressive assumptions).
Frequently Asked Questions
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