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Measure a rectangle, triangle, circle, trapezoid or irregular lot in feet, yards, meters, chains or miles. Get acres, square feet, hectares and fence length in one step, then add several parcels into a combined total.
Quick answer: 1 acre = 43,560 square feet = 4,046.86 square meters = 0.4047 hectares. To get acres from a rectangle measured in feet, multiply length × width, then divide by 43,560.
Every calculation converts your measurements to a common unit, finds the area, then divides by one acre (43,560 square feet, or 4,046.8564 square meters).
| Shape | Area formula | Notes |
|---|---|---|
| Rectangle or square | Area = length × width | Opposite sides must be equal and corners square |
| Triangle (base and height) | Area = ½ × base × height | Height is measured at a right angle to the base |
| Triangle (three sides) | Area = √(s(s−a)(s−b)(s−c)), s = (a+b+c) ÷ 2 | Heron’s formula; the sides must satisfy the triangle inequality |
| Circle | Area = π × radius² | Diameter ÷ 2 = radius |
| Trapezoid | Area = ½ × (A + B) × height | A and B are the two parallel sides |
| Irregular lot | Shoelace formula on corner coordinates | Works for any simple (non-crossing) polygon |
200 × 400 = 80,000 square feet. 80,000 ÷ 43,560 = 1.8365 acres, which is 1 acre and about 36,440 square feet.
π × 100² = 31,415.9 square feet. 31,415.9 ÷ 43,560 = 0.7212 acres.
½ × 300 × 200 = 30,000 square feet. 30,000 ÷ 43,560 = 0.6887 acres.
120 × 85 = 10,200 square meters, which is 1.02 hectares. 10,200 ÷ 4,046.86 = about 2.52 acres.
Corners at (0, 0), (300, 0), (300, 150), (150, 260) and (0, 200) feet give an area of 65,250 square feet, or 1.4979 acres. Press “Load an example” in the Irregular lot tab to see it calculated.
Typical lot dimensions converted to acres (rounded to four decimals):
| Lot size (ft) | Square feet | Acres |
|---|---|---|
| 50 × 100 | 5,000 | 0.1148 |
| 60 × 120 | 7,200 | 0.1653 |
| 75 × 125 | 9,375 | 0.2152 |
| 100 × 100 | 10,000 | 0.2296 |
| 100 × 150 | 15,000 | 0.3444 |
| 100 × 200 | 20,000 | 0.4591 |
| 150 × 200 | 30,000 | 0.6887 |
| 200 × 200 | 40,000 | 0.9183 |
| 200 × 300 | 60,000 | 1.3774 |
| 300 × 300 | 90,000 | 2.0661 |
| 330 × 660 | 217,800 | 5.0000 |
| Acres | Square feet | Square meters | Hectares |
|---|---|---|---|
| 0.1 | 4,356 | 404.69 | 0.0405 |
| 0.25 | 10,890 | 1,011.71 | 0.1012 |
| 0.5 | 21,780 | 2,023.43 | 0.2023 |
| 1 | 43,560 | 4,046.86 | 0.4047 |
| 2 | 87,120 | 8,093.71 | 0.8094 |
| 5 | 217,800 | 20,234.28 | 2.0234 |
| 10 | 435,600 | 40,468.56 | 4.0469 |
| 20 | 871,200 | 80,937.13 | 8.0937 |
| 40 | 1,742,400 | 161,874.26 | 16.1874 |
| 100 | 4,356,000 | 404,685.64 | 40.4686 |
| 640 (1 square mile) | 27,878,400 | 2,589,988.11 | 258.9988 |
An acre is a measure of area, not a shape, so there are endless ways to lay one out. A few useful versions:
| Shape of one acre | Dimensions |
|---|---|
| Square | 208.71 ft × 208.71 ft (about 63.6 m per side) |
| Surveyor’s original | 1 chain × 1 furlong = 66 ft × 660 ft |
| Long narrow strip | 100 ft × 435.6 ft |
| Typical rectangle | 150 ft × 290.4 ft, or 200 ft × 217.8 ft |
| Compared with a football field | About three-quarters of one (57,600 sq ft with both end zones, or 1.32 acres) |
One acre is also exactly 160 square rods, and 640 acres make one square mile (a “section” in US land surveys).
Use this calculator for planning, pricing and comparison. For property lines, sales, fencing along a boundary or building permits, a licensed land surveyor’s measurement is the legal source of truth.
This calculator uses the international acre: exactly 4,046.8564224 square meters, or 43,560 square feet based on the international foot (0.3048 m). Older US land records used the US survey foot (about 0.30480061 m). That makes a survey acre roughly 0.17 square feet larger, a difference too small to matter for any normal parcel. The US survey foot was officially retired by NIST on January 1, 2023.
One acre is 43,560 square feet. That is the same as 4,046.86 square meters, 4,840 square yards or 0.4047 hectares.
Multiply length by width (both in feet) to get square feet, then divide by 43,560. For example, 200 ft × 400 ft = 80,000 sq ft, and 80,000 ÷ 43,560 = 1.8365 acres. If you measure in meters, divide the square meters by 4,046.86 instead.
100 × 100 = 10,000 square feet, and 10,000 ÷ 43,560 = 0.2296 acres. That is a little under a quarter of an acre.
Use the Irregular lot tab and enter the corner coordinates in order. The calculator applies the shoelace formula. Or split the lot into rectangles and triangles, calculate each, and use “Add to combined total”.
One hectare is 2.47105 acres, and one acre is 0.404686 hectares. To convert, multiply hectares by 2.47105 to get acres, or acres by 0.404686 to get hectares.
There is no single answer because an acre is an area. As a square it is about 208.7 ft × 208.7 ft. Other common layouts are 150 × 290.4 ft, 200 × 217.8 ft, or the surveyor’s 66 × 660 ft.
A square mile contains exactly 640 acres.
Not always. Deeds often say “more or less”, and older records may be rounded or based on an earlier survey. A recent boundary survey by a licensed surveyor is the authoritative figure.
Small differences usually come from rounding, an older survey, GIS boundaries that are drawn approximately, or measuring a slightly different shape. Differences of a few hundredths of an acre are common.
No. Everything is calculated in your browser, and nothing you type is sent to our servers.
Unit definitions follow the international acre (43,560 square feet, 4,046.8564224 m²) as published by NIST Special Publication 811. Each worked example on this page was recalculated by hand against the formulas shown. Results are estimates for planning and comparison and are not a legal survey. See our editorial policy for how we build and review tools.