Estimate Lot Yield From One Parcel

Somebody pulls out a calculator at the kitchen table, divides the total acreage by a target lot size, and announces "we can get twenty lots." That napkin number ignores roads, setbacks, utility easements, odd-shaped remainders, and minimum-frontage rules—so the real lot yield ends up closer to fourteen. The gap between gross area and net developable area is where most first-time subdivision plans fall apart, and it is exactly what this tool is built to expose before you pay an engineer to draw something that won’t get approved.

Enter parcel dimensions, pick a division mode, set your road reserve and minimum lot constraints, and see how many sellable lots actually fit. The result is a planning-grade estimate—useful for comparing parcels, screening deals, or briefing a surveyor. It is not a preliminary plat and does not replace your local planning department.

Gross area is the deed acreage—everything inside the boundary lines. Net developable areais what remains after you subtract roads, perimeter setbacks, utility easements, stormwater ponds, and any required open space. Typical residential subdivisions lose 20–30 % of gross area to infrastructure; tighter urban sites can lose closer to 35 %.

Until you know the net number, you don’t know your lot count. A 5-acre parcel at 25 % deduction leaves 3.75 sellable acres. At a 7,500 sq ft minimum lot size that’s roughly 21 lots—not the 29 you get by dividing the full 5 acres. Ignoring the deduction overstates yield by almost 40 %.

Lot count is never limited by just one rule. The constraint that binds first—the one that cuts yield the most—depends on the parcel shape, the zone, and how you lay out the roads. Here is a quick reference for the usual suspects.

Run the planner once with each constraint on its own, then all together. The difference shows you which rule is actually driving the yield down.

• Flag lots. Long, narrow access strips ("flagpoles") eat frontage but add almost no buildable area. A 20-ft-wide flagpole running 150 ft to reach a back lot consumes 3,000 sq ft of gross area and contributes zero usable frontage to any other lot.
• Cul-de-sac loss. A standard 50-ft-radius turnaround bulb takes roughly 7,850 sq ft. On a 3-acre parcel that can be 6 % of the total area—enough to lose an entire lot.
• Irregular remainders. After filling a grid of rectangular lots, the leftover triangle or wedge is often too small or too oddly shaped to meet minimum-lot standards. The planner reports this as residual area so you can decide whether to absorb it into an adjacent lot or set it aside as open space.
• Utility easement deductions. A 20-ft sewer easement running diagonally through the middle of a parcel can slice a row of lots in half. If you know the easement width and path, subtract that corridor from gross area before you run the planner, or model it as additional road reserve.

How much area do roads really take? A single 24-ft-wide street running 400 ft consumes 9,600 sq ft. Add a cul-de-sac bulb and that jumps past 17,000 sq ft. Two streets plus a turnaround can eat 20–30 % of a mid-size parcel.

Can I fit more lots by going narrower? Narrower frontage means more lots along the road, but each lot must still meet the minimum-area rule. At some point the lots become too deep relative to their width, and many codes reject aspect ratios above 3:1 or 4:1. The planner flags when frontage and area constraints conflict.

What if the zoning changes mid-project? Run the planner with both the current and proposed rules. If the new minimum-lot size drops from 10,000 to 7,500 sq ft, you might gain three or four extra lots—or none if frontage was already the binding constraint. Knowing which rule actually limits yield tells you whether a rezoning petition is worth the cost.

Does the tool handle phased development? Not directly, but you can run separate sessions for each phase. Model Phase 1 on the front half of the parcel and Phase 2 on the back half, then compare total lot yield to a single full-parcel run.