Field Acreage Calculator

Frequently Asked Questions

How many square feet are in an acre?

Exactly 43,560 square feet. The calculator divides your field area in square feet by this number to give acres.

How do I find the acreage of an irregular field?

Divide the shape into rectangles and triangles, compute each area, and add them. A triangle is one-half times base times height.

How many acres are in a hectare?

A hectare is about 2.471 acres, so one acre is roughly 0.4047 hectares. The calculator reports the hectare equivalent automatically.

Is a GPS area reading good enough?

GPS is fast and within a few percent for field-management decisions, but it drifts several feet and is not legally binding. Use a licensed survey for sales or easements.

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Estimates for informational purposes only.

Important Disclaimer: Estimates for informational purposes only.

This calculator provides estimates for informational purposes only. Results are based on assumptions and may not reflect actual outcomes. Consult qualified professionals in relevant fields before making important decisions based on these results.

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How This Calculator Works

An acre is an oddly specific unit - exactly 43,560 square feet, the area a team of oxen could plow in a day - which makes converting a field's dimensions into acres a chore done wrong as often as right. This calculator takes a field's length and width in feet, multiplies them for the area in square feet, then divides by 43,560 to give acres, the unit that drives seed orders, input rates, cash rent, and assessments. It also reports the raw square footage and the metric equivalent in hectares, so the same measurement serves a domestic seed bag, an international spec sheet, or a deed description. For a clean rectangle the answer is exact; for irregular fields, see the notes below on breaking the shape into pieces.

Formula / Method

Area (sq ft) = length (ft) × width (ft). Acres = area (sq ft) ÷ 43,560, the exact number of square feet in one acre. Hectares = acres × 0.4047, since one acre is about 0.4047 hectares (a hectare is 10,000 square meters, roughly 2.471 acres). Both length and width must be positive or the tool declines to compute. The formula assumes a rectangle measured on flat ground; steep slopes inflate the surface area you walk but not the mapped (planimetric) acreage that deeds and rates use, so measure the horizontal distance.

Worked Example

A field measuring 660 ft by 660 ft. Area = 660 × 660 = 435,600 square feet. Acres = 435,600 ÷ 43,560 = exactly 10 acres - not a coincidence, since 660 ft is a furlong, the classic length tied to the acre. In metric that is 10 × 0.4047 ≈ 4.047 hectares. A 200 ft by 300 ft house lot, by contrast, is 60,000 sq ft ÷ 43,560 ≈ 1.38 acres.

Irregular Fields

Real fields are rarely tidy rectangles. The reliable approach is to divide the shape into rectangles and triangles, compute each piece, and add the areas - a triangle is ½ × base × height. For a true four-sided lot with no right angles, surveyors use the trapezoid or the coordinate "shoelace" method on corner coordinates. Curved boundaries along a creek or road can be approximated by many thin strips. When you only have one length and width that bound an irregular field, you will overestimate, so subtract the obvious cut-outs. For anything that affects a sale, easement, or tax line, a licensed survey is the only authoritative source.

Surveyor's vs GPS & Old Units

GPS area tools (a phone app, a tractor display, or a handheld unit walked around the perimeter) are fast and good to within a few percent for field-management decisions, but consumer GPS drifts several feet and is not legally binding. A licensed surveyor using total stations or RTK GPS ties the corners to recorded monuments and produces the acreage of record. You may still meet older units: a rood is a quarter-acre (10,890 sq ft), a square perch (or rod/pole) is 272.25 sq ft and there are 160 of them in an acre, and 640 acres make a section (one square mile). When a deed reads in chains, recall that a chain is 66 ft and ten square chains equal one acre - the same furlong logic behind the 660 ft example above.

Frequently Asked Questions

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