Also called an acre calculator, this tool finds the acreage of any lot or field and converts between units.
How to calculate acres
An acre is 43,560 square feet. To find acreage, calculate the area in square feet (length × width for a rectangle) and divide by 43,560. If you measure in yards divide by 4,840; in meters divide by 4,046.86.
Example: a 660 ft × 330 ft field is 217,800 sq ft ÷ 43,560 = 5 acres.
Area formulas for common shapes
| Shape | Area formula |
|---|---|
| Rectangle / square | Length × Width |
| Triangle | ½ × Base × Height |
| Triangle (3 sides) | √[s(s−a)(s−b)(s−c)] where s = (a+b+c)÷2 (Heron’s formula) |
| Circle | π × Radius² |
| Trapezoid | ½ × (A + B) × Height |
| Any polygon | Shoelace formula from corner coordinates |
Choose the shape in the calculator, enter your measurements in feet, yards, meters, rods, chains or miles, and the results appear in acres, square feet, square yards, square meters, hectares and square miles.
How to measure an irregular field
- Break it into simple shapes. Divide the field into rectangles and triangles, calculate each and add them. The Several sections option does this for rectangles.
- Use corner coordinates. If you have coordinates for each corner (from a survey plat or a local grid), paste them into the Irregular option and the shoelace formula gives the exact area.
- Use a GPS or mapping tool. Walk or drive the boundary with a GPS app or trace it on a satellite map. This is fast, though accuracy depends on the device.
- Check the deed or survey. The recorded acreage on the deed or a professional survey is the authority for legal and sale purposes.
For property sales, boundaries and legal descriptions, use a licensed surveyor. This calculator is for planning, estimating and everyday farm use.
Converting between acres and square feet
The Unit converter shape handles acres, square feet, square yards, square meters, hectares and square miles in either direction: pick your starting unit and it converts to all the others at once.
Finding acreage with a map
Prefer to trace a boundary on a satellite map rather than measure it by hand? This page does not embed a live map, but you can measure a lot with any mapping tool and bring the numbers here:
- Open a satellite map tool that shows a measuring or area tool (several free map and GPS apps offer this).
- Trace the boundary of your lot or field, corner to corner, and read off the area or the corner coordinates.
- If the tool gives you an area directly, use the Unit converter above to convert it to acres.
- If it gives you corner coordinates instead, paste them into the Irregular (corner coordinates) shape here for an exact acreage using the shoelace formula.
Map-based tracing is convenient but only as accurate as the imagery and your tracing; for anything legal or financial, confirm with a licensed survey.
Four-sided lots and other related calculations
A four-sided lot is either a trapezoid (if two sides are parallel, use the Trapezoid shape) or a general quadrilateral (use Irregular with the four corner coordinates, or Several sections if you can split it into rectangles).
Once you have your acreage, a few related, but different, calculations come up often:
- Fencing: the Perimeter (fence line) result above gives the fence length for whatever shape you entered.
- Price or cost per acre: enter a price per acre in the optional field above for the total value of the parcel at that rate.
- Livestock stocking rate: how many cattle or sheep a parcel supports depends on forage type, rainfall and management, not on area alone, so it is a separate calculation from acreage. As a very rough, non-authoritative starting point, extension guides often cite roughly 1 to 2 acres per cow-calf pair on productive pasture; get a local stocking-rate recommendation before planning a herd.
- Trees per acre: tree count depends on planting spacing, not area alone: trees per acre ≈ 43,560 ÷ (row spacing x tree spacing, in feet), the same math as the plant population calculator uses for crops.
- Lime rate: this depends on your soil test (target pH and buffer pH), not on acreage alone; a soil test report gives a rate in tons or pounds per acre to multiply by your measured acres.
Acre conversion table
| Unit | Equals 1 acre | 1 unit in acres |
|---|---|---|
| Square feet | 43,560 | 0.0000230 |
| Square yards | 4,840 | 0.000207 |
| Square meters | 4,046.86 | 0.000247 |
| Hectares | 0.4047 | 2.4711 |
| Square miles | 0.0015625 (1/640) | 640 |
| Square rods | 160 | 0.00625 |
| Square chains | 10 | 0.1 |
Common acre sizes
| Fraction of an acre | Square feet | Approx. square |
|---|---|---|
| 1/10 acre | 4,356 | 66 × 66 ft |
| 1/5 acre | 8,712 | 93 × 93 ft |
| 1/4 acre | 10,890 | 104 × 104 ft |
| 1/2 acre | 21,780 | 148 × 148 ft |
| 1 acre | 43,560 | 209 × 209 ft |
| 2 acres | 87,120 | 295 × 295 ft |
| 5 acres | 217,800 | 467 × 467 ft |
| 10 acres | 435,600 | 660 × 660 ft |
| 40 acres | 1,742,400 | 1,320 × 1,320 ft (¼ mile) |
| 160 acres | 6,969,600 | 2,640 × 2,640 ft (½ mile) |
| 640 acres | 27,878,400 | 1 square mile |
For scale: a football field with end zones (360 × 160 ft) is about 1.32 acres; one acre is roughly 209 feet on each side.
Surveyor’s units: rods and chains
Old deeds and surveys often use rods and chains: 1 rod = 16.5 ft, 1 chain = 66 ft (4 rods), and 10 square chains = 1 acre. The calculator supports both, so you can enter dimensions straight from a legal description.
What to do with your acreage
Once you know how many acres you have, work out the time and cost of the job: acres per hour calculator for tractors, sprayers and mowers, mowing time, bush hogging cost and land clearing cost.
Spraying? Divide your acres by tank coverage with the sprayer gallons per acre calculator. Planting or reseeding? Multiply by your rate in the seeding rate calculator and check stand counts with the plant population calculator. Cutting brush? See the bush hog acres per hour calculator.
Frequently asked questions
How many square feet are in an acre?
43,560 square feet. That is about 208.7 ft by 208.7 ft if the acre is a square.
How do I calculate acreage from length and width?
Multiply length by width in feet to get square feet, then divide by 43,560. For example, 500 ft × 400 ft = 200,000 sq ft ÷ 43,560 = 4.59 acres.
How do I find the acreage of an irregular lot?
Split it into rectangles and triangles and add the areas, use the corner-coordinates option, or trace the boundary on a GPS or mapping tool. For legal purposes, use a survey.
How many acres is a quarter-mile square?
A square measuring ¼ mile (1,320 ft) on each side is 40 acres. A half-mile square (2,640 ft) is 160 acres, and a full mile square is 640 acres.
How many acres is 1/4 acre in square feet?
1/4 acre is 10,890 square feet, about 104 ft × 104 ft.
How do I convert hectares to acres?
Multiply hectares by 2.471 to get acres. Use the Unit converter option to convert between acres, hectares, square feet, square meters and more.
Is there a square feet to acreage calculator?
Yes: choose Square feet as the starting unit in the Unit converter shape, and it returns acres along with square yards, square meters and hectares.
I searched for an acre an hour calculator. Is that this page?
Probably not: “acre an hour” usually means a coverage rate for equipment, which is the acres per hour calculator. This page measures the size of land (acreage), not how fast a machine covers it.
Sources and further reading
Concepts on this page: Acre · Hectare · Shoelace formula · Heron's formula
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