The factor is exact, and it never changes
An acre is defined as 66 feet by 660 feet — one chain by one furlong — which is exactly 43,560 square feet. That figure has been fixed since it was set in English law under Edward I and has never changed. A common shortcut is to divide square feet by 43,500 for a quick, close estimate.
Common lot and parcel sizes
| Acres | Square feet | Roughly |
|---|---|---|
| 0.10 | 4,356 | Small urban lot |
| 0.25 | 10,890 | Typical suburban lot |
| 0.50 | 21,780 | Large suburban lot |
| 1 | 43,560 | Small farm or paddock |
| 2 | 87,120 | |
| 5 | 217,800 | Working farmland |
| 10 | 435,600 | Smallholding |
| 40 | 1,742,400 | Quarter-quarter section |
There are 640 acres in a square mile, so an acre is 1/640 of a square mile — handy for reading survey descriptions.
Where the conversion goes wrong
- Not 40,000. An acre is 43,560 square feet, not a rounded 40,000. The gap is over 3,500 square feet, enough to matter in a land deal.
- Acres vs hectares. An acre is about 0.4047 hectares, and one hectare is 2.47 acres. They are not interchangeable.
- Area, not length. An acre measures surface, not a distance. It has no fixed shape — a square acre is about 208.7 feet on each side, but a long thin acre is just as valid.
Common questions
How many square feet are in an acre?
Exactly 43,560 square feet. The number is fixed by definition: an acre is 66 feet by 660 feet, one chain by one furlong.
How do I convert square feet to acres in my head?
Divide by about 43,500. So 87,000 square feet is roughly 2 acres. For an exact figure, divide by 43,560.
How big is an acre compared with a football field?
An acre is a bit smaller. A US football field including both end zones is about 1.32 acres, so an acre is close to three-quarters of the field.
What is a typical suburban lot in acres?
Most suburban lots run 0.2 to 0.33 acres, which is 8,700 to 14,400 square feet. Half an acre is a large lot, and anything over an acre is usually rural.
