Buildable Area Calculator: What Can I Build on My Lot?
See what you can build on your lot
Draw or size your lot, set the zoning numbers, and get your buildable envelope, footprint and floor area in seconds — a planning-stage estimate, not a survey.
1 Lot · 2 Setbacks · 3 Zoning · 4 Fits
Lot size & setbacks
Zoning
Zoning caps
What fits on this lot
Want a direct read on your actual parcel — whether it fits the house you have in mind, and what the numbers really allow? That’s what Office Hours is for: a free, focused session on your site, no obligation.
Illustrative planning estimate. Setback geometry is approximate on irregular or concave lots, and figures depend on your jurisdiction’s exact rules — always confirm your parcel’s numbers with the local planning department.
What to read next
Tell us where you are and we’ll point you to the reads that fit.
Draw or size your lot, set the zoning numbers, and get your buildable envelope, footprint and floor area in seconds — a planning-stage estimate, not a survey.
What is buildable area?
Buildable area is the portion of a lot you can legally build on after setbacks are subtracted and coverage, FAR and height limits are applied — not the lot's total size. A 6,000 sq ft lot rarely gives you 6,000 sq ft to build on; setbacks alone often cut it by a third or more.
This tool tests the envelope: footprint and floor area from your lot shape and zoning inputs. It can't see easements, overlays, slope, or flood and coastal rules, so treat the result as a well-informed estimate. We're expanding it over time.
The four rules that decide what fits
Setbacks — required distance from each boundary (front, sides, rear); they define the buildable envelope.
Lot coverage — the share of the lot your footprint can cover, typically 35–50% for single-family zoning.
Floor area ratio (FAR) — total floor area allowed across all storeys, as a multiple of lot area. FAR 0.5 on a 6,000 sq ft lot = 3,000 sq ft. Many single-family districts don't use FAR at all.
Height limit — how tall you can go, which sets how many storeys fit under the caps.
Frequently asked questions
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Whichever runs out first. You might have coverage allowing a 2,400 sq ft footprint but setbacks leaving room for only 1,800 — so setbacks govern and the extra coverage is meaningless. Example: a 60 × 100 ft lot with 20 ft front/rear and 5 ft side setbacks leaves a ~3,000 sq ft envelope, but a 40% coverage limit caps the footprint at 2,400 sq ft, so coverage governs. The calculator names the binding rule every time.
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Subtract the setback from every boundary to get the buildable envelope, then apply your coverage and FAR caps. The smallest result is your limit — which is what this calculator computes automatically.
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FAR is permitted floor area divided by lot area. FAR 0.6 on a 5,000 sq ft lot allows 3,000 sq ft across all storeys.
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In most US single-family (R-1) zoning: front 20–25 ft, sides 5–10 ft, rear 15–25 ft. These are set locally and vary by district — confirm yours with the planning department.
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No. It's a planning-stage estimate to help you understand trade-offs and ask better questions.
Get a professional read on your lot
The calculator gives you the shape of what's possible. Office Hours gives you the answer.
It's a free, focused session with an architect on your parcel — the things this tool can't see: easements and overlays, slope, flood and coastal rules, and what the numbers actually mean for the house you have in mind, its cost, and its design. No pitch, no obligation — just a straight, expert read on where you stand and what to do next.
If you're weighing a lot, a plan, or whether to build at all, this is the fastest way to replace a good estimate with a real one.