Estimate Units Allowed From Density Rules

Residential density is the number of dwelling units per acre of land, expressed as units per acre (DU/acre). It's calculated by dividing the total number of dwelling units by the site area in acres: Density = Number of Dwelling Units ÷ Site Area (acres). For example, 20 units on a 2-acre site equals a density of 10 units per acre (20 ÷ 2 = 10). This metric is fundamental to zoning regulations and helps communities manage growth, infrastructure capacity, and neighborhood character. Density applies to all housing types including single-family homes, townhomes, apartments, and accessory dwelling units (ADUs). Understanding residential density is essential for land development planning and zoning compliance.

Gross density uses the total site area including all land within the parcel boundaries, such as roads, open space, wetlands, and other non-buildable areas. This provides an overall sense of how densely an area is developed. Net density uses only the developable portions of the site, excluding constrained areas like public rights-of-way, critical areas (wetlands, floodplains, steep slopes), dedicated open space, and other areas where building is prohibited or restricted. The same number of units will always result in a higher net density than gross density because net excludes non-buildable areas. Your local zoning code will specify which calculation method applies to your district—always check your zoning ordinance to determine whether to use gross or net area in your calculations. Understanding gross vs. net density is essential for accurate density calculations.

No, this calculator does not look up or interpret zoning codes. It simply performs the mathematical calculation of units divided by acres and compares your result to any maximum or minimum density values you enter manually. You must research your local zoning ordinance separately and enter those values manually for comparison. Zoning codes are specific to each jurisdiction and can be found on your city or county's planning department website. This tool is designed for planning purposes only and does not provide professional zoning interpretation or final development capacity determinations. Always consult your local planning department for official zoning information and compliance verification.

Check your local zoning ordinance, which is usually available on your city or county's planning department website. Look for your property's zoning district designation (e.g., R-1, R-2, R-3, MF-1, MF-2), then find the dimensional standards or development standards section for that district. The density limits will be listed as maximum and/or minimum units per acre. You can also contact your local planning department directly for assistance, or use online zoning map tools if your jurisdiction provides them. Some jurisdictions have interactive zoning maps that show your property's zoning district when you enter an address. Understanding how to find zoning limits is essential for accurate density compliance assessment.

Units per acre applies to all housing types but translates differently depending on the product. For single-family homes, it typically translates to lot sizes (e.g., 4 units/acre = roughly 10,000 sq ft lots, meaning each lot is about 0.25 acres). For townhomes, 10–15 units/acre is common, with each unit typically occupying 2,000–5,000 sq ft including shared walls and common areas. For apartments, density can range from 20–60+ units/acre depending on building height, with garden apartments (2–3 stories) at 15–25 units/acre and high-rise apartments (7+ stories) at 60–200+ units/acre. The same density can look very different depending on the housing product—higher density doesn't necessarily mean taller buildings, as townhomes can achieve moderate density through efficient site design. Understanding how density translates to different housing types helps you interpret density values in context.

Minimum density requirements encourage efficient land use, particularly near transit, employment centers, and urban cores. They help support public transit ridership by ensuring adequate population density to make transit viable, maximize housing production in high-demand areas where land is scarce and expensive, ensure adequate population to support neighborhood retail and services, and prevent land speculation that holds parcels for future higher-value uses instead of current development. Minimum density requirements are increasingly common in urban areas and transit-oriented development zones as cities seek to address housing shortages and promote sustainable development patterns. Understanding minimum density requirements helps you see why they exist and how they shape development.

Not always. While you may be allowed a certain density by the zoning code, other regulations often further limit actual development capacity. Setbacks (required distances from property lines) may reduce buildable area, height limits may cap the number of stories you can build, parking requirements may consume significant land area, open space minimums may require dedicating land for landscaping or recreation, lot coverage limits may restrict how much of the site can be covered by buildings, floor area ratio (FAR) limits may cap total building square footage, and environmental constraints (wetlands, floodplains, steep slopes) may reduce developable area. This calculator only addresses density—a full development analysis requires evaluating all applicable standards. Understanding that density is one factor among many helps you assess development capacity accurately.

Many jurisdictions offer density bonuses that allow developers to exceed base zoning limits in exchange for providing public benefits like affordable housing, public amenities, or green building features. For example, including 15% affordable units might grant a 35% density bonus, allowing you to build 35% more units than the base maximum. Bonus programs vary by jurisdiction and may require specific percentages of affordable housing, public open space, transit improvements, or other community benefits. The bonus is typically calculated as a percentage increase over the base maximum density. Check with your local planning department about available bonus programs, eligibility requirements, and application procedures. Understanding bonus density programs helps you maximize development potential while providing community benefits.

Use the total number of dwelling units, including affordable units, accessory dwelling units (ADUs), and any other residential units. Density calculations typically count all dwelling units regardless of price point or unit type. However, some bonus density programs may calculate certain unit types differently (e.g., affordable units may count differently for bonus calculations), so check your local regulations. The general rule is to count all residential units that will be built on the site, including market-rate apartments, affordable units, townhomes, single-family lots, and ADUs. Understanding unit counting helps you calculate density accurately.

You can enter your site area in square feet, and the calculator will convert it to acres automatically using the standard conversion factor of 43,560 square feet per acre. For example, 108,900 square feet ÷ 43,560 = 2.5 acres. If you enter both acres and square feet, the acres value will be used. You can verify the conversion in the results to ensure accuracy. This conversion is essential because density is always expressed in units per acre, regardless of how you measure your site area. Understanding square feet to acres conversion helps you use the calculator effectively with different measurement units.

The mathematical calculations are accurate to the values you enter. However, the results are only as accurate as your inputs. Ensure you're using the correct site area (gross vs. net as required by your code), counting all dwelling units correctly, and entering the right density limits from your zoning district. This tool performs simple mathematical calculations only and does not interpret zoning codes, account for other zoning standards, or provide professional planning determinations. This tool is for planning purposes only—official determinations require review by local planning officials and qualified professionals. Understanding accuracy limitations helps you use the tool appropriately.

You can use the optional scenario label field to name different concepts (e.g., 'Townhome Option A', 'Apartment Concept B'), then use the download feature to save a text report for each scenario. This allows you to compare different unit counts, layouts, or housing mixes for the same site. Each scenario will show its own density calculation and comparison to your entered limits. Comparing scenarios helps you evaluate different development options and understand how unit count, site area, and density limits interact. Understanding scenario comparison helps you make informed development planning decisions.