Lot Size Calculator (USA)
Measure a residential lot from its frontage and depth — rectangular or irregular. Add front, rear and side setbacks to estimate the buildable footprint, and a price per square foot to value the parcel.
Lot area = frontage × depth.
Estimates the buildable footprint after required yard setbacks. Set all to 0 to ignore.
Enter a market price per square foot to estimate the lot's total value.
| Unit | Value |
|---|---|
| Calculate to see all conversions | |
How to use the lot size calculator
Four quick steps turn frontage and depth into total lot size — with acres, the buildable footprint left after setbacks, an estimated lot value, and a downloadable PDF.
Pick the lot shape
Rectangular for a standard lot, or irregular if the front and rear widths differ.
Enter frontage and depth
Work in feet, yards, or meters — switching the unit re-reads every measurement.
Add your setbacks
Front, rear, and side. The diagram redraws the buildable envelope as you type.
Read results & save a PDF
Lot size, acres, buildable footprint, coverage, value, and a to-scale diagram.
How lot size and buildable area are calculated
Two calculations run here: the lot itself, and the envelope left inside it once the required yards are taken off. Setbacks come off the depth once each and off the width twice. Here is the exact math.
Worked example — a 75 × 120 ft lot with 25 / 20 / 10 ft setbacks
Lot area: 75 × 120 = 9,000 sq ft
Acres: 9,000 ÷ 43,560 = 0.207 acres
Buildable width: 75 − (2 × 10) = 55 ft
Buildable depth: 120 − 25 − 20 = 75 ft
Footprint: 55 × 75 = 4,125 sq ft
≈ 0.207 acres of lot, with 4,125 sq ft buildable — 45.8% maximum coverage.
Lot size & setback charts
The lookups that come up when sizing a residential lot — common dimensions, how much survives typical setbacks, what setbacks to expect by zone, and the unit conversions behind it all.
| Lot size | Square feet | Acres | Buildable* | Coverage |
|---|---|---|---|---|
| 40 × 100 ft | 4,000 sq ft | 0.092 ac | 1,100 sq ft | 27.5% |
| 50 × 100 ft | 5,000 sq ft | 0.115 ac | 1,650 sq ft | 33.0% |
| 60 × 120 ft | 7,200 sq ft | 0.165 ac | 3,000 sq ft | 41.7% |
| 75 × 120 ft | 9,000 sq ft | 0.207 ac | 4,125 sq ft | 45.8% |
| 80 × 125 ft | 10,000 sq ft | 0.230 ac | 4,800 sq ft | 48.0% |
| 100 × 150 ft | 15,000 sq ft | 0.344 ac | 8,400 sq ft | 56.0% |
| 150 × 200 ft | 30,000 sq ft | 0.689 ac | 20,150 sq ft | 67.2% |
*Buildable figures assume 25 ft front, 20 ft rear, and 10 ft side setbacks. Notice the pattern: narrow lots lose a far bigger share, because the side setback is deducted twice from a smaller width.
| Zone type | Front | Rear | Side (each) |
|---|---|---|---|
| Urban infill / small lot | 10–20 ft | 15–20 ft | 3–5 ft |
| Standard suburban (R-1) | 25–30 ft | 20–25 ft | 5–10 ft |
| Large lot / estate | 35–50 ft | 30–50 ft | 15–25 ft |
| Rural / agricultural | 50–100 ft | 50 ft+ | 25–50 ft |
Planning ballparks only. Your actual numbers come from the municipal zoning code for your specific parcel — and corner lots, flag lots, and waterfront parcels often follow different rules.
| Convert | Multiply / divide | Where it’s used |
|---|---|---|
| Sq ft → acres | ÷ 43,560 | US lot and land sizing |
| Sq ft → sq m | × 0.092903 | Metric site plans |
| Sq m → sq ft | × 10.764 | Reading an overseas listing |
| Sq ft → sq yd | ÷ 9 | Older deeds and surveys |
| Acres → hectares | × 0.4047 | Quoting a US parcel abroad |
| $ per sq ft → $ per acre | × 43,560 | Comparing lot and land pricing |
Match the price basis to the area unit before comparing rates — suburban lots are usually quoted per square foot, rural land per acre.
| Lot size | Acres | Rough comparison |
|---|---|---|
| 2,500 sq ft | 0.057 ac | Urban row-house lot |
| 5,000 sq ft | 0.115 ac | Compact subdivision lot |
| 10,890 sq ft | 0.250 ac | Quarter-acre benchmark |
| 21,780 sq ft | 0.500 ac | Large suburban lot |
| 43,560 sq ft | 1.000 ac | ~¾ of a football field |
| 217,800 sq ft | 5.000 ac | Small hobby farm |
The calculator shows the same comparison live — football fields, basketball courts, and tennis courts — as you change the dimensions.
Frontage is the street-facing edge, depth runs back from it, and every setback is measured inward from a property line — which is why the buildable envelope always sits inside the lot, never on it.
- Side setbacks count twice — a 10 ft side yard takes 20 ft off the width, which is why narrow lots lose the largest share.
- Corner lots usually get two fronts — both street-facing edges take the front setback, so enter the larger figure to stay conservative.
- Irregular lots use a trapezoid — the average of front and rear width times depth gets close, but curves and jogs need the plat.
Everything the calculator works out
One frontage and depth gives you the full picture — the lot in every unit, what’s left inside the setbacks, what it’s worth, and a diagram that shows both at once.
The figures behind every lot calculation
Built for anyone working out what fits
A lot you’re buying, a house you’re planning, or an addition you’re squeezing in — the same measurements answer all three, once the setbacks are in.
Checking whether a listed lot is really as big as it sounds, and what the asking price works out to per square foot.
- Compare against the listed square footage
- Price it per sq ft to compare deals
- Confirm dimensions on the plat
Finding out whether the house they have in mind actually fits inside the setbacks before paying for a single drawing.
- Enter setbacks from the zoning code
- Compare the envelope to your footprint
- Check the coverage cap separately
Quoting lot size accurately in a listing, or checking whether a rear addition has room to go before pitching it to a client.
- Quote both sq ft and acres
- Test the rear setback first
- Save the PDF for the file
7 tips for measuring a lot accurately
Small habits that keep a lot estimate honest — and stop you designing a house that can’t be permitted.
Lot size calculator FAQ
The lot size, setback, coverage, and land value questions people ask most before buying or building.
Multiply the frontage by the depth. A lot 75 feet wide and 120 feet deep is 9,000 square feet, or about 0.207 acres.
If the lot narrows or widens toward the rear, average the front and rear widths first: (front + rear) ÷ 2 × depth. That trapezoid approximation covers most irregular residential lots.
Most US subdivision lots fall between 5,000 and 12,000 square feet, with the quarter-acre lot at 10,890 sq ft often used as the benchmark.
Urban infill lots run smaller at 2,500 to 5,000 square feet, while rural and estate lots start around half an acre and go up from there.
A setback is the minimum distance a structure must sit from a property line, set by your local zoning code. Front and rear setbacks come off the depth once each, and the side setback comes off the width twice — once on each side.
On a 75 × 120 ft lot with 25 ft front, 20 ft rear, and 10 ft side setbacks, the buildable envelope shrinks to 55 × 75 ft, or 4,125 square feet.
For a lot with parallel front and rear boundaries of different widths, use the trapezoid formula: add the front and rear widths, divide by two, and multiply by the depth. A lot 80 ft at the front, 60 ft at the rear, and 120 ft deep works out to 8,400 sq ft.
Lots with curves, jogs, or non-parallel sides need to be split into pieces or measured from the recorded plat.
Lot coverage is the share of the parcel a structure occupies, expressed as a percentage. The figure shown here is the maximum coverage the setback envelope allows — the largest footprint that fits inside the required yards.
Many zoning codes impose a separate coverage cap, often 30 to 50 percent for residential zones, so the real limit is whichever number is lower.
A 75 by 120 foot lot is 9,000 square feet, which comes to 0.207 acres — roughly a fifth of an acre, or 836 sq m.
That’s a common suburban lot size, a little smaller than the quarter-acre benchmark of 10,890 square feet.
Multiply the lot area by the going rate per square foot for comparable land nearby. At $30 a square foot, a 9,000 sq ft lot comes to $270,000.
Urban and suburban lots are usually quoted per square foot while rural land is quoted per acre, so convert before comparing — one dollar per square foot equals $43,560 an acre. Frontage, access, utilities, zoning, and topography move the rate far more than raw area does.
No. This is a planning estimate calculated from the dimensions you enter, and the buildable figure applies only the setbacks you type in. It doesn’t know your jurisdiction’s actual zoning, easements, right-of-way, floodplain, or coverage caps.
For a permit application, a deed, a mortgage, or a boundary dispute you need the recorded plat and a licensed surveyor. Use this to size up a lot before that stage.
Not a Survey — Planning Estimate Only: This calculator computes lot area, unit conversions, and a buildable envelope from the dimensions and setbacks you enter, treating the parcel as an idealized rectangle or trapezoid. Actual boundaries are established only by a licensed surveyor and the recorded plat or legal description, and results here carry no legal standing for permitting, deeds, financing, boundary disputes, or subdivision. The buildable footprint applies only the setback values you type in and does not reflect your jurisdiction’s actual yard requirements, corner-lot rules, easements, right-of-way, floodplain, height limits, or maximum lot coverage — confirm all of those with your local planning or zoning department before designing anything. Lot value is a simple rate multiplication and is not an appraisal; access, utilities, zoning, topography, and frontage materially affect real market value. For planning purposes only.