What to measure
How to use the acreage calculator
Pick the shape, enter the measurements in feet, yards, miles or meters, and read the area in acres. Add a price per acre to estimate the land’s value.
The formula
- Rectangle: acres = length × width ÷ 43,560 (in feet)
- Triangle: acres = ½ × base × height ÷ 43,560
- Circle: acres = π × (diameter ÷ 2)² ÷ 43,560
Worked example: a 300 × 200 ft lot
- 300 × 200 = 60,000 sq ft
- 60,000 ÷ 43,560 = 1.377 acres (0.557 hectares)
- The same base and height as a triangle: 0.689 acres
Common sizes
| Area | Acres |
|---|---|
| 1 square mile | 640 |
| 1 hectare | 2.471 |
| Quarter-acre lot (≈ 104 × 104 ft) | 0.25 |
| Football field with end zones | 1.32 |
Common lot sizes
Width × depth in feet, as lots are often listed. Your deed or plat has the exact figures.
| Lot | Square feet | Acres | Hectares |
|---|---|---|---|
| 50 × 100 ft | 5,000 | 0.115 | 0.046 |
| 60 × 120 ft | 7,200 | 0.165 | 0.067 |
| 100 × 100 ft | 10,000 | 0.23 | 0.093 |
| 75 × 150 ft | 11,250 | 0.258 | 0.105 |
| 100 × 200 ft | 20,000 | 0.459 | 0.186 |
| 150 × 300 ft | 45,000 | 1.033 | 0.418 |
| 330 × 660 ft | 217,800 | 5 | 2.023 |
| 660 × 660 ft | 435,600 | 10 | 4.047 |
Common mistakes
- Treating every lot as a rectangle. If the sides aren’t parallel, length × width is wrong; split the lot into rectangles and triangles.
- Mixing up feet and square feet. A square acre is about 208.7 ft on a side, but its area is 43,560 sq ft.
- Measuring over hills with a wheel or tape. The tape follows the ground, so a sloping lot measures bigger than its mapped area.
- Relying on your own measurement for a sale or a fence line. Use the survey or plat for anything legal.
Frequently asked questions
How many square feet are in an acre?
43,560. An acre is also 4,840 square yards, about 4,047 square meters or 0.405 hectares.
How big is an acre in feet?
A square acre is about 208.7 ft on each side. Any shape works as long as the area is 43,560 sq ft, for example 66 × 660 ft, the original "furlong by chain".
How do I calculate the acreage of an irregular lot?
Split it into rectangles and triangles, calculate each piece, and add them. For property boundaries that matter legally, use the survey or plat on your deed.
How many acres is a football field?
An American football field including both end zones is 360 × 160 ft. That's 57,600 sq ft, or about 1.32 acres.
How many acres is a 100 × 200 ft lot?
0.459 acres. At 20,000 sq ft, it's a little under half an acre.
What are the dimensions of 5 acres?
Any shape with 217,800 sq ft. A 330 × 660 ft rectangle is exactly 5 acres; 660 × 660 ft is 10 acres.
Is a 75 × 150 ft lot a quarter acre?
Just over. It's 11,250 sq ft, or 0.258 acres. A 100 × 100 ft lot is smaller, at 0.23 acres.
How many acres is 100,000 square feet?
About 2.3 acres (100,000 ÷ 43,560 = 2.296).
Sources
Formulas and defaults last reviewed October 30, 2026. How we check our math.