Acreage Calculator for Fields and Land

Square feet to acres

One acre equals 43,560 square feet. For a rectangular field, multiply length by width in feet, then divide by 43,560. Acres = length × width ÷ 43,560. To convert back, multiply acres by 43,560.

A 660 ft × 660 ft field: 660 × 660 = 435,600 square feet; 435,600 ÷ 43,560 = 10 acres.

Triangular corners and trapezoids

For a triangular field corner, multiply the base by the perpendicular height and divide by two. For a trapezoid, average the two parallel sides, then multiply by the perpendicular distance between them. Divide either square-foot result by 43,560.

A triangle with a 400 ft base and 300 ft perpendicular height: 400 × 300 ÷ 2 = 60,000 square feet, or about 1.3774 acres.

Center-pivot circle acreage

Use the pivot's effective watered radius in feet, not its diameter. Circle acres = π × radius² ÷ 43,560. This models a full circle; a partial sweep, end gun, roads and unwatered areas change the actual covered area.

A 1,250 ft full-circle radius covers approximately 112.6891 acres before accounting for those exclusions.

Irregular fields and GPS boundaries

Break an irregular field into non-overlapping rectangles and triangles and add their areas, or enter its GPS corners in perimeter order. The GPS tool uses a local projection and rejects malformed, duplicated or crossing points. It supports 3–500 points within one degree of latitude and longitude, away from the poles.

Exclude buildings, waterways and other non-cropped areas when estimating planted acres. GPS quality, boundary placement and projection distortion affect the estimate. Use a licensed surveyor when an official area or boundary is required.

Use field acreage for farm planning

A measured field area helps you plan seed, fertilizer and work. For example, a separately chosen rate of 150 lb of product per acre across a 10-acre field requires 1,500 lb. That multiplication is planning arithmetic, not a recommended application rate.

In CropBuddy, draw field boundaries on the field map and organize farm work alongside your fields. Continuing from this calculator carries your estimate in this browser tab; it does not automatically create a field or save a surveyed boundary.

How many square feet are in an acre?

An acre contains 43,560 square feet. A square acre is about 208.71 ft on each side; an acre does not have to be square.

Can I calculate acreage without GPS?

Yes. Measure in feet with a tape or measuring wheel and select the matching shape. Use perpendicular height for triangles and trapezoids. Split irregular areas into simpler, non-overlapping shapes.

What does the regular polygon option calculate?

It assumes every side is the same length and every interior angle is equal. Enter a whole number of at least three sides. Equal side lengths alone do not make an irregular field a regular polygon.

Is a GPS acreage estimate an official survey?

No. It is approximate and cannot establish legal boundaries, certified acreage or survey-grade accuracy. Check coordinates and exclusions; consult a licensed surveyor for official measurements.

Do I need an account to use the acreage calculator?

No. All six calculations and the square-foot conversion are free without registration. A CropBuddy account is optional if you want to continue to the farm's field map and manage your work.