Acres to Square Feet Calculator
Convert acres to square feet: 1 acre = 43,560 sq ft, exactly and by definition. Type either box — the conversion runs both ways.
Last updated:Conversion Formula
Conversion factors follow NIST Special Publication 811, Appendix B.9.1 (area). Links are in Sources below.
square feet = acres × 43,560
acres = square feet ÷ 43,560 (1 sq ft = 1/43,560 acre = 0.00002295684 acre)
Neither direction involves a measured constant, so there is no rounding error to worry about: 43,560 is the definition. Other units one acre equals exactly: 4,840 sq yd, 160 square rods, 10 square chains, 0.0015625 sq mi.
Worked Example
A listing says a parcel is 2.5 acres. How much floor area or land area is that in square feet?
- Write the factor: 1 acre = 43,560 sq ft.
- Multiply: 2.5 × 43,560 = 108,900 sq ft.
- Check by dividing back: 108,900 ÷ 43,560 = 2.5 acres. ✓
Mental version: 2.5 × 44,000 = 110,000, minus 1% (1,100) = 108,900. The shortcut is exact because 44,000 × 0.99 = 43,560.
Quick Reference
| Acres | Square Feet |
|---|---|
| 1/8 acre | 5,445 |
| 1/4 acre | 10,890 |
| 1/3 acre | 14,520 |
| 1/2 acre | 21,780 |
| 3/4 acre | 32,670 |
| 1 acre | 43,560 |
| 2 acres | 87,120 |
| 5 acres | 217,800 |
| 10 acres | 435,600 |
| 20 acres | 871,200 |
| 40 acres | 1,742,400 |
| 100 acres | 4,356,000 |
| 160 acres (quarter section) | 6,969,600 |
| 640 acres (1 section = 1 sq mi) | 27,878,400 |
What is an acre?
An acre is a unit of area equal to 43,560 square feet. It predates the metric system and predates the United States: the word comes from the land a yoke of oxen could plough in a day, which is why the classic acre is a long narrow strip rather than a square — 660 ft × 66 ft, one furlong by one chain. A chain is 66 ft (100 links of Gunter's chain), and ten square chains make an acre.
In the Public Land Survey System that still describes most land west of the Appalachians, a section is one square mile = 640 acres. Halving a section twice gives the quarter-quarter section of 40 acres — the "forty" of "back to the forty." A township is 36 sections, so 36 × 640 = 23,040 acres per nominal township.
One acre also equals 4,840 square yards and 160 square rods, both of which come from the same chain arithmetic: 22 yd × 220 yd and 20 rods × 8 rods.
What is a square foot?
A square foot is the area of a square one foot on each side: 12 in × 12 in = 144 sq in, or 0.09290304 m² exactly (NIST SP 811 prints 9.290 304 E−02 m²). It is the unit US real-estate listings, floor plans, and flooring orders use, which is why an acreage figure has to be converted before you can compare it to a house size or order materials.
Multiplying 43,560 sq ft by 0.09290304 m² per sq ft gives 4,046.8564224 m² for an acre built on the international foot, and 0.40468564224 hectares.
What shape is an acre?
Any shape whose length × width product is 43,560 sq ft. The rectangles that come out whole are worth memorising because deeds and fence quotes use them:
| Shape | Dimensions | Check |
|---|---|---|
| Square | 208.71 ft × 208.71 ft (BLM prints 208 ft 8 in) | √43,560 = 208.7103 |
| Classic plough strip | 660 ft × 66 ft | 1 furlong × 1 chain |
| Wide rectangle | 264 ft × 165 ft | 4 chains × 2.5 chains |
| Near-square rectangle | 198 ft × 220 ft | 3 chains × 3⅓ chains |
| Circle | radius 117.75 ft, diameter 235.50 ft | √(43,560 ÷ π) = 117.7522 |
| House lot frontage | 100 ft frontage × 435.6 ft deep | 100 × 435.6 = 43,560 |
If you know the acreage but not the shape, you cannot recover the side lengths — 1 acre as a 100 ft × 435.6 ft strip and 1 acre as a 208.71 ft square fence very differently (1,071 ft of fence versus 835 ft). Use the property size calculator when you have two sides and an angle instead of an area.
Survey foot versus international foot
You will occasionally see an acre quoted as 4,046.87 m² instead of 4,046.86 m². Both are defensible; they use different feet.
- International foot (used for everything new): 1 ft = 0.3048 m exactly, so 1 acre = 43,560 × 0.3048² = 4,046.8564224 m² exactly.
- US survey foot: 1 ft = 1200/3937 m ≈ 0.30480061 m, so 1 acre ≈ 4,046.8726 m². NIST SP 811 lists this variant as 4.046 873 E+03 m² and labels it "based on U.S. survey foot."
- The gap is about 4.1 parts per million in area (2 ppm in length, per the Federal Register notice). On a 40-acre farm that is roughly 0.007 acres — invisible for fencing, visible if you are reconciling a 1950s deed against a modern GIS layer.
The US survey foot was deprecated on December 31, 2022; from January 1, 2023 the international foot supersedes it in all applications (85 FR 62698). Older state-plane coordinate data may still carry survey-foot values, which is the usual reason two authoritative sources disagree in the sixth digit.
FAQ
How many square feet are in one acre?
Exactly 43,560. Half an acre is 21,780 sq ft, a quarter acre is 10,890 sq ft, and an eighth of an acre is 5,445 sq ft. The figure is definitional, not measured, so it never needs rounding.
How do I convert acres to square feet without a calculator?
Multiply by 43,560. A mental shortcut that lands on the exact answer: multiply by 44,000, then take 1% off, because 44,000 × 0.99 = 43,560. For 2.5 acres that is 110,000 − 1,100 = 108,900 sq ft.
What are the dimensions of one acre?
An acre can be any shape as long as length × width = 43,560 sq ft. As a square it is 208.71 ft on each side, which the BLM land-description diagram prints as 208 ft 8 in. The historic strip is 660 ft × 66 ft (one furlong by one chain); other exact rectangles are 264 × 165 ft and 198 × 220 ft. As a circle it has a radius of 117.75 ft.
Is a US survey acre different from an international acre?
Yes, by about 4 parts per million. NIST SP 811 lists the acre based on the US survey foot as 4.046 873 E+03 m², while 43,560 international-foot squares give exactly 4,046.8564224 m². The survey foot was deprecated on December 31, 2022, so new work uses the international foot; the two still agree to 43,560 sq ft.
How many square feet are in a quarter acre, half acre, or 40 acres?
A quarter acre is 10,890 sq ft, a half acre is 21,780 sq ft, and 40 acres (a quarter-quarter section, traditionally called a forty) is 1,742,400 sq ft. One full section of 640 acres is 27,878,400 sq ft, which is also one square mile.
How do I convert square feet back to acres?
Divide by 43,560, or multiply by 1/43,560 = 0.00002295684. Example: 108,900 sq ft ÷ 43,560 = 2.5 acres. Type into the second box of the converter above and it runs this direction automatically, or use the square feet to acres page.
Sources and How to Check This Page
- Area factors — acre, square foot, square yard, square mile, hectare — come from NIST Special Publication 811, Appendix B.9.1: square foot 9.290 304 E−02 m², acre (based on U.S. survey foot) 4.046 873 E+03 m², square yard 8.361 274 E−01 m², square mile 2.589 988 E+06 m².
- The survey-foot retirement is 85 FR 62698, FR Doc. 2020-21902: use of the US survey foot was deprecated on December 31, 2022, and the notice states the 2 parts per million length difference. NIST's companion table gives 1 international foot = 0.999 998 US survey foot exactly.
- Acre geometry (43,560 sq ft; 660 ft × 66 ft; 160 square rods; 208 ft 8 in square; 640 acres = 1 sq mile = 1 section; 66 ft = 1 chain) is transcribed from the BLM Land Description Diagram and the BLM Module 2 PLSS study guide, which adds that an acre "is approximately the land contained in a 209 foot by 209 foot square."
- Every other number on this page is arithmetic on those factors and can be re-derived: 43,560 × 0.3048² = 4,046.8564224; √43,560 = 208.7103; √(43,560 ÷ π) = 117.7522; 640 × 43,560 = 27,878,400. Nothing here depends on a rounded constant.
- What this page does not claim: lot sizes, home sizes, or land values. Those vary by market and need their own sources — see home size and property size for the sourced figures.