How to calculate acreage
For a rectangular lot, multiply length by width in feet to get square feet, then divide by 43,560.
The formula
Acres = length (ft) × width (ft) ÷ 43,560
Worked example
A lot 200 feet by 300 feet is 60,000 square feet, or 1.38 acres.
How to use this calculator
Enter the lot length and lot width in feet. The acreage calculator converts the area to acres and also shows square feet, hectares, square meters and the perimeter. Add a price per acre if you want to work with a land price. If you measured in yards or meters, convert both sides to feet first. If the lot is not a rectangle, break it into simple shapes and add the results.
What the result means
An acre is a measure of area, not a shape. Any lot that covers 43,560 square feet is one acre, whether it is square, long and narrow, or irregular. Common fractions are easy to remember:
- A quarter acre is 10,890 square feet.
- Half an acre is 21,780 square feet.
- One acre is 43,560 square feet.
More examples
| Lot size (ft) | Square feet | Acres |
|---|---|---|
| 100 × 100 | 10,000 | 0.23 |
| 150 × 200 | 30,000 | 0.69 |
| 200 × 300 | 60,000 | 1.38 |
| 330 × 660 | 217,800 | 5.00 |
Measuring in yards
A field 100 yards by 150 yards is 15,000 square yards. Multiply by 9 to get 135,000 square feet, then divide by 43,560. The field is about 3.10 acres.
Measuring in meters
A plot 50 meters by 80 meters is 4,000 square meters. One square foot is 0.092903 square meters, so divide by 0.092903 to get about 43,056 square feet. That is about 0.99 acres.
A triangular lot
Multiply the base by the height and divide by 2. A triangle with a 200 foot base and a 150 foot height is 15,000 square feet, or about 0.34 acres.
What changes the result
- Shape. Length times width works only for rectangles. A lot with angled sides is smaller than the rectangle that surrounds it.
- Units. Mixing feet on one side with yards on the other gives a wrong answer.
- Where you measure from. A fence or a hedge is not always on the property line. Your survey shows the legal boundary.
Common mistakes
- Dividing by 43,560 when the area is in square yards or square meters.
- Treating an irregular lot as a full rectangle.
- Adding the side lengths together. That gives the distance around the lot, not its area.
- Rounding too early. Keep the square feet exact and round the acres at the end.
Related calculators
If you already know the area, the square feet to acres converter and the acres to square feet converter are quicker. To measure a building or a room on the lot, use the square footage calculator.
Frequently asked questions
How do I measure an irregular lot?
Split it into rectangles and triangles, calculate each and add them.
How big is one acre?
43,560 square feet. As a square it is about 208.7 feet on each side.
Where can I find my lot size?
On your deed, survey or county assessor record.
How many square feet is a quarter acre?
10,890 square feet, which is 43,560 divided by 4.
How many acres is a 100 by 100 foot lot?
100 × 100 = 10,000 square feet, which is about 0.23 acres.
How do I convert square yards to acres?
Divide by 4,840. One acre is 43,560 square feet, and 43,560 ÷ 9 = 4,840 square yards.
Does an acre have to be square?
No. An acre is any shape that covers 43,560 square feet.