Lot Size Calculator — acres, square feet and metres
A lot's area from frontage and depth in square feet, acres, square metres and hectares with exact factors, and any acreage drawn as a square.
A lot’s area from its frontage and depth, in square feet, acres, square metres and hectares with the exact factors — and the other way, what an acre looks like as a square.
Quick answer: common lot sizes
| Frontage × depth | Square feet | Acres | Square metres |
|---|---|---|---|
| 25 × 100 ft | 2,500 | 0.057 | 232.3 |
| 50 × 100 ft | 5,000 | 0.115 | 464.5 |
| 50 × 150 ft | 7,500 | 0.172 | 696.8 |
| 60 × 120 ft | 7,200 | 0.165 | 668.9 |
| 75 × 150 ft | 11,250 | 0.258 | 1,045.2 |
| 100 × 100 ft | 10,000 | 0.23 | 929 |
| 100 × 200 ft | 20,000 | 0.459 | 1,858.1 |
An acre is 43,560 sq ft exactly. A 50 × 100 ft lot is 5,000 sq ft, about 0.115 acre; it takes 8.7 of them to make an acre.
| Square feet | — |
|---|---|
| Acres | — |
| Square metres | — |
| Hectares | — |
| Square yards | — |
| The acres above, as a square | — |
An acre is 43,560 square feet, and nobody can picture that. It is a square 208.71 feet on a side, or a 66 × 660 foot strip, a chain by a furlong, which is where the number comes from. A 100 × 150 foot city lot is 0.344 acre; a quarter-acre lot is 10,890 square feet, about 100 × 109. The last row draws any acreage as a square so a listing’s number turns into a shape.
Frontage times depth is the rectangle, and most lots are not. A flag lot, a pie-shaped corner or a lot with a rear jog is two rectangles, so the page takes a second piece. Beyond that, the survey is the answer: it carries the metes and bounds, and area from a deed’s bearings and distances is a calculation this page does not attempt. What it does do is convert the survey’s figure exactly.
The factors are definitions. 1 ft² = 0.09290304 m², 1 acre = 43,560 ft² = 4,046.8564224 m², 1 hectare = 10,000 m² = 2.4711 acres. Rounded conversions drift by a parking space on a large parcel; these do not.
An acre is ten square chains, which is how old deeds count it. NIST's 2020 notice on the survey foot (85 FR 62698) tabulates the exact relationships: 1 acre = 43,560 ft² = 10 square chains = 160 square rods, with the chain at 66 ft and the rod at 16.5 ft. A deed that runs a lot 4 chains one way and 2.5 chains the other is describing 10 square chains, exactly one acre, 264 × 165 ft. Multiply chains by 66 and rods by 16.5 before entering them here.
Since 2023 the United States has one foot again. The U.S. survey foot, 1200/3937 m, is to be avoided after December 31, 2022 except for historic and legacy records, and the international foot is 0.3048 m exactly; the acre on it is exactly 4,046.8564224 m². The two feet differ by 2 parts per million, so an acre measured in survey feet is 4 ppm larger, 0.016 m², and a 640-acre section 10.4 m². It never matters on a house lot. It matters when a pre-2023 coordinate in survey feet meets a new one in international feet, which is why NIST asks for the labels sft and ift, and sac for a survey acre.
What I check on a job
Where the two numbers came from. Before I use the area, I find out whether the frontage and depth came from a survey or from a listing, and when there is a survey I take its figures and nobody else's. Then I run frontage times depth and compare the product with the area the survey states. If they match, the rectangle is a fair stand-in for this lot; if they disagree, it is not, and the survey's area is the one I carry forward. With a second piece I sketch the split first, so the two rectangles meet along one line and never overlap; a strip counted twice reads as land the owner does not have. And I treat a listing's acreage as a range: an area rounded to two decimal places of an acre can be off by about 218 square feet either way.
Area = frontage × depth (+ the second piece). 1 acre = 43,560 ft² (66 × 660 ft); 1 ft² = 0.09290304 m² (exact); 1 ha = 10,000 m²; a square acre is √43,560 = 208.71 ft on a side.
Worked example
A lot with 100 ft of frontage and 150 ft of depth: how many acres?
- 100 × 150 = 15,000 ft².
- ÷ 43,560 = 0.344 acre; × 0.09290304 = 1,393.55 m² (0.139 ha).
- For scale, one acre is a square 208.71 ft on a side.
A third of an acre. A 40 × 60 ft rear piece brings it to 17,400 ft², 0.399 acre — two rectangles is as far as arithmetic goes; after that it is the survey.
11 values on this page were driven in a browser and compared with independently derived figures on 2026-10-29 (2808 values across 228 calculators site-wide).
Questions
How many square feet in an acre?
43,560 — a square about 208.7 ft on a side, or 66 × 660 ft. A quarter acre is 10,890 ft².
How do I calculate lot size in acres?
Frontage × depth in feet, ÷ 43,560. A 100 × 150 ft lot is 0.344 acre; an irregular lot is the survey's figure, which this page converts exactly.
How big is a quarter-acre lot?
10,890 ft², about 100 × 109 ft. A full acre is 43,560 ft², a square 208.71 ft on a side, or the 66 × 660 ft strip (a chain by a furlong) the number comes from.
How do I size a flag lot or a pie-shaped corner?
As two rectangles: frontage × depth for the main piece and a second piece for the jog or flag. Beyond that the survey is the answer; area from a deed's bearings and distances is a calculation this page does not attempt.