Square feet to acres
Convert square feet to acres. Divide by 43,560 for an exact result, with a table of common US residential lot sizes.
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The formula
acres = square feet ÷ 43,560The 43,560 is exact. An acre is 4840 square yards and a square yard is 9 square feet, so an acre is exactly 43,560 square feet. There is no rounding in this conversion at all.
Quick reference
| Square feet | Acres |
|---|---|
| 1000 ft² | 0.023 ac |
| 5000 ft² | 0.115 ac |
| 10,000 ft² | 0.230 ac |
| 21,780 ft² | 0.5 ac |
| 43,560 ft² | 1 ac |
| 87,120 ft² | 2 ac |
| 435,600 ft² | 10 ac |
Residential lots
This conversion exists almost entirely for one purpose: American property listings give the house in square feet and the land in acres, so comparing two plots means converting one of them.
| Lot size | Square feet | Acres |
|---|---|---|
| Small urban lot | 3000 ft² | 0.069 ac |
| Typical suburban lot | 8000 ft² | 0.184 ac |
| Quarter acre | 10,890 ft² | 0.25 ac |
| Third of an acre | 14,520 ft² | 0.333 ac |
| Half acre | 21,780 ft² | 0.5 ac |
| One acre | 43,560 ft² | 1 ac |
A “quarter-acre lot” is 10,890 ft², which is roughly 104 feet square. Zoning minimums are frequently written in acres while plat maps are dimensioned in feet, so both numbers appear in the same document describing the same land.
Building coverage
Coverage ratios are where the two units meet in practice:
| Lot | House | Coverage |
|---|---|---|
| 0.25 ac (10,890 ft²) | 2000 ft² | 18.4% |
| 0.25 ac (10,890 ft²) | 3000 ft² | 27.5% |
| 0.5 ac (21,780 ft²) | 3000 ft² | 13.8% |
| 1 ac (43,560 ft²) | 3000 ft² | 6.9% |
A useful landmark
An acre is roughly 209 feet square. √43,560 = 208.7. An acre is not square by definition — it was originally a long thin strip, one furlong by one chain — but picturing a 209-foot square is the fastest way to judge whether a plot is anywhere near one.
For the metric equivalent, an acre is 4046.9 m², or about 63.6 metres square. See acres to hectares.