What this calculator does
Turn acres into square feet, or square feet into acres, to compare lot sizes at a glance. In the United States, house lots are often described in two ways that rarely line up. The listing says "0.25 acre" while the survey or tax record gives the area in square feet. Builders, landscapers and buyers often switch between the two to compare lots, plan a fence or estimate how much sod or seed to buy.
The acre was historically the land a team of oxen could plough in a day, standardized as a strip one furlong (660 ft) long and one chain (66 ft) wide. That is 660 × 66 = 43,560 square feet, which remains the exact definition. A square foot is the area of a square one foot on each side.
Where it's used
Why this math matters outside the classroom:
- Lot sizes. A quarter-acre lot is 43,560 ÷ 4 = 10,890 ft².
- Listing comparisons. Home buyers turn a 7,500 ft² lot into about 0.17 acres to compare it with listings given in acres.
- Lawn care. A half-acre yard is 21,780 ft², the unit that seed and fertilizer rates per 1,000 ft² are based on.
- Football fields. An American football field with both end zones is 360 × 160 ft, or 57,600 ft², about 1.32 acres.
- Zoning rules. Planners convert a 1 acre minimum lot size into 43,560 ft² to check a subdivision plan drawn in feet.
Grade level and standards: Grades 5–6; Common Core State Standards for Mathematics 5.MD.A.1, 6.RP.A.3.d. © Copyright 2010. National Governors Association Center for Best Practices and Council of Chief State School Officers. All rights reserved.
How to use it
- Enter the area in acres or square feet. Use decimals for partial acres, such as 0.33.
- Choose acres to square feet, or square feet to acres.
- Read the result. The table lists common lot sizes in the chosen direction.
What the inputs mean
- Value to convert
- An area in acres (for ac → ft²) or square feet (for ft² → ac).
- Direction
- Which way to convert.
Formula and method
ft² = ac × 43,560 ac = ft² ÷ 43,560
In the formulas, ac is the area in acres and ft² is the area in square feet. Both directions use the same whole number, 43,560, so both are exact. The calculator works through the shared metric base (1 acre = 4,046.8564224 m², 1 ft² = 0.09290304 m²) and the ratio comes out to 43,560.
Dividing by 43,560 often gives a repeating decimal: 10,000 ft² is 0.229568… acres.
Worked example
A quarter-acre lot: how many square feet is it?
- The factor is exact: 1 ac = 43,560 ft².
- 0.25 × 43,560 = 10,890.
Result: A quarter acre is 10,890 ft².
Understanding the result
To picture an acre, imagine a square about 208.7 feet on each side, since √43,560 ≈ 208.71. An American football field without the end zones (300 × 160 ft = 48,000 ft²) is a bit larger than an acre.
Mental shortcut: 1 acre ≈ 44,000 ft², so a lot in square feet divided by 44,000 gives acres about 1% low. A 7,500 ft² lot is exactly 0.1722 acres; the shortcut gives 0.170.
Common lot sizes: 1/8 acre is 5,445 ft²; 1/3 acre is 14,520 ft²; half an acre is 21,780 ft²; 2 acres is 87,120 ft².
Assumptions and limitations
- The acre is the international acre of 43,560 international square feet.
- Land listed in US survey acres differs by about 4 parts per million, negligible for house lots.
- Recorded lot areas can include easements or rights-of-way; check the survey for what was measured.
Frequently asked questions
How many square feet are in an acre?
Exactly 43,560 square feet.
Does an acre have to be square?
No. An acre is an amount of area in any shape. A strip 66 ft wide and 660 ft long, a 208.7 ft square, or an irregular lot can all be one acre.
How many acres is 10,000 square feet?
About 0.2296 acres, a little under a quarter acre.
Is an acre the same in every country?
The international acre is the same wherever it is used today, including the US, UK, Canada and Australia. Some historical regional acres were larger, but they are no longer in official use.
How this calculator is checked
Method: 1 acre = 1 furlong × 1 chain = 660 ft × 66 ft = 43,560 ft² (international foot). The calculation is covered by automated tests with known reference values and edge cases. Last updated 2026-10-18. Found a problem? Tell us.
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