Square Feet to Acres Calculator
Convert between square feet and acres in both directions. 1 acre = 43 560 sq ft (the area of a 66 ft × 660 ft chain-and-furlong rectangle from English measurement history).
Last updated: September 2026
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About this calculator
1 acre = 43 560 square feet. This peculiar number comes from English measurement history: 1 acre = 1 chain (66 ft) × 1 furlong (660 ft) = 66 × 660 = 43 560 sq ft. The chain and furlong were designed to be practical field measurements for medieval English farmers, and the acre was the amount of land a yoke of oxen could plough in a day.
Quick conversion facts: 1 acre = 43 560 sq ft ≈ 4 047 sq m. 1 hectare (metric) = 10 000 sq m = 2.471 acres. 1 square mile = 640 acres = 27 878 400 sq ft. A US Public Land Survey System (PLSS) section is 1 square mile; a "quarter section" is 160 acres, and a "quarter-quarter" is 40 acres — the smallest standard PLSS division and a common land-grant unit.
Typical US lot sizes: urban row house 0.05–0.1 ac, dense suburb 0.15–0.25 ac, standard suburb 0.3–0.5 ac, large suburban 0.5–2 ac, exurban 2–10 ac, rural residential 5–40 ac. Zoning minimum lot sizes vary widely — check the municipal zoning code before assuming a lot can be subdivided.
How to use
Example — 87 120 sq ft to acres. 87 120 / 43 560 = 2 acres exactly. Example — 0.5 acres to sq ft. 0.5 × 43 560 = 21 780 sq ft. That is a comfortable half-acre suburban lot, roughly 148 ft × 147 ft if square.
Frequently asked questions
Why 43,560 sq ft in an acre?
1 acre = 1 chain × 1 furlong = 66 ft × 660 ft. The chain (66 ft) and furlong (660 ft) were standardized in English measurement long before decimal metric, and the historical acre was designed to be the amount of land a team of oxen could plough in a day. 66 × 660 = 43 560 — the same number appears everywhere in US land records because of this history.
How does an acre compare to a hectare?
1 hectare = 10 000 sq m = 107 639 sq ft = 2.471 acres. So a hectare is about 2.5× an acre. Metric-country farmers work in hectares; US farmers work in acres. USDA still reports crop yields in acres for domestic statistics.
Are all "acres" the same size?
The international acre (0.4047 hectare) is standard. The US survey acre (used for PLSS land records) is fractionally larger — about 0.0004 hectare more — due to a 1959 US foot redefinition. The difference (2 ppm) matters only for extremely precise land surveys.
What is a section, quarter-section, or 40?
A PLSS section is 1 square mile = 640 acres. A quarter-section is 160 acres = 1/4 mile × 1/4 mile. A quarter-quarter (a "40") is 40 acres. Federal land grants — Homestead Act, railroad grants, mineral rights — were typically issued in these units and are still referenced in US land deeds.