A field area calculator converts field dimensions into acreage and other area units used in agriculture and land planning. Whether you're calculating field size for seed orders, fertilizer applications, or crop insurance, this tool handles rectangular, triangular, and trapezoidal fields with automatic conversion between acres, hectares, square feet, and square meters.
Field Area Calculator
Area Unit Conversions
| From | To Acres | To Hectares | To Sq Ft |
|---|---|---|---|
| 1 acre | 1.000 | 0.4047 | 43,560 |
| 1 hectare | 2.471 | 1.000 | 107,639 |
| 1 sq mile | 640 | 258.9 | 27,878,400 |
How to Calculate Field Area
Accurate field area measurement is the foundation of farm planning — seed rates, fertilizer applications, yield estimates, and crop insurance all depend on knowing how many acres or hectares you're working with. This field area calculator converts field dimensions to all common area units instantly.
Rectangular Fields
Most farm fields are roughly rectangular. Measure the length and width (GPS devices, wheel measures, or pacing work). Multiply length × width in feet and divide by 43,560 for acres. A classic 40-acre field is 1,320 ft × 1,320 ft (¼ mile × ¼ mile = 1/16 section = 40 acres).
Triangular Fields
Fields bounded by roads at angles often form triangles. For a right triangle, area = (base × height) / 2. Measure the two perpendicular sides and divide the product by 87,120 for acres.
GPS and Mapping Tools
For highly irregular fields, use GPS devices, smartphone mapping apps (Google Maps area measurement, OnX, or agriculture-specific tools), or county assessor parcel data which typically includes legal acreage. Hand measurement works for rectangular fields; GPS is better for complex shapes.
Frequently Asked Questions
Is this field area calculator free?
Yes, completely free with no signup. All calculations run in your browser.
How do I convert square feet to acres?
Divide square feet by 43,560 to get acres. For example, 87,120 sq ft = 2 acres. This calculator converts automatically to all common area units.
How many square feet is one acre?
One acre equals 43,560 square feet, 4,840 square yards, or 0.4047 hectares. One hectare equals 2.471 acres or 10,000 square meters.
How do I calculate acres for a rectangular field?
For a rectangle: multiply length × width in feet, then divide by 43,560. For example, a 660 ft × 660 ft field = 435,600 sq ft ÷ 43,560 = 10 acres.
Can this tool calculate irregular fields?
Yes for right triangles and trapezoids. For truly irregular fields, break them into triangles and rectangles, calculate each section separately, and add the results.