How to calculate acreage
Find the area in square feet, then divide by 43,560, the number of square feet in an acre.[1] For a rectangle that is length × width; for other shapes, split the land into pieces and add them.
- Rectangle: length × width. 100 × 200 ft = 20,000 sq ft ÷ 43,560 = 0.459 acres.
- Triangle: base × height ÷ 2, where the height is measured square to the base.
- Trapezoid (a lot wider at the back than the front): (front + back) ÷ 2 × depth. 80 and 120 ft wide, 150 ft deep = 15,000 sq ft = 0.344 acres.
- Odd shapes: divide the plot into rectangles and triangles and add them, as shown in how to measure irregular areas.
acres = square feet ÷ 43,560 · hectares = square meters ÷ 10,000
Acres to square feet, square meters and hectares
One acre is 43,560 sq ft, 4,840 sq yd, 4,046.86 m² or 0.4047 hectares; a hectare is 10,000 m².[1][3]
| Acres | Square feet | Square yards | Square meters | Hectares |
|---|---|---|---|---|
| 0.25 | 10,890 | 1,210 | 1,012 | 0.101 |
| 0.5 | 21,780 | 2,420 | 2,023 | 0.202 |
| 1 | 43,560 | 4,840 | 4,047 | 0.405 |
| 2 | 87,120 | 9,680 | 8,094 | 0.809 |
| 5 | 217,800 | 24,200 | 20,234 | 2.023 |
| 10 | 435,600 | 48,400 | 40,469 | 4.047 |
| 40 | 1,742,400 | 193,600 | 161,874 | 16.187 |
How big is an acre?
A square acre is about 208.7 ft on each side, because 208.7 × 208.7 ≈ 43,560 sq ft. An acre does not have to be square: it is also 10 square chains or 160 square rods,[1] so a strip 66 ft wide and 660 ft long (1 chain by 10 chains) is an acre too.
Common lot sizes in acres
A 50 × 100 ft city lot is 0.115 acres; a 100 × 200 ft lot is 0.459 acres; you need about 209 × 209 ft for a full acre.
| Lot (ft) | Square feet | Acres | Hectares |
|---|---|---|---|
| 50 × 100 | 5,000 | 0.115 | 0.046 |
| 60 × 120 | 7,200 | 0.165 | 0.067 |
| 75 × 150 | 11,250 | 0.258 | 0.105 |
| 100 × 100 | 10,000 | 0.23 | 0.093 |
| 100 × 200 | 20,000 | 0.459 | 0.186 |
| 150 × 300 | 45,000 | 1.033 | 0.418 |
| 208.7 × 208.7 | 43,556 | 1 | 0.405 |
| 330 × 660 | 217,800 | 5 | 2.023 |
Survey feet and the acre
Since January 1, 2023, NIST says the old US survey foot should be avoided except for historic and legacy work, and the acre is now defined with the international foot of exactly 0.3048 m.[2] The survey-foot acre was about 4,046.8726 m², only 0.016 m² larger,[1] which makes no difference for a home lot or a field.
Common acreage mistakes
The most common mistake is multiplying the frontage by the depth on a lot that is not rectangular; use the trapezoid or split the lot instead.
- Mixing units: feet times meters gives nonsense. Pick one system; the calculator switches between feet and meters.
- Slanted sides: the height of a triangle or trapezoid is measured square to the base, not along the slanted side.
- Using the calculator for a legal boundary: the deed or a licensed survey is the official acreage; this tool is for estimates.
Seeding or covering the land?Seed rates are often given per 1,000 sq ft or per acre: see the grass seed calculator. For areas in square yards, use the square yard calculator.
Frequently asked questions
How many square feet are in an acre?
43,560 square feet, which is 4,840 square yards or about 4,046.86 square meters.[1]
How many acres is 100 by 200 feet?
100 × 200 = 20,000 sq ft ÷ 43,560 = 0.459 acres.
How do I calculate the acreage of an irregular lot?
Split it into rectangles, triangles and trapezoids, find each area in square feet, add them and divide by 43,560. The calculator adds the pieces for you.
How many acres is a hectare?
One hectare is 10,000 m², or about 2.471 acres. One acre is about 0.405 hectares.[3]