Square Feet to Acres Converter
Convert square feet to acres — 43,560 to the acre, and where that came from.
Updated
acres
1.0000ac
43,560 sq ft = 1.0000 ac
In short
How many square feet are in an acre?
Exactly 43,560 square feet. Divide your square footage by 43,560 to get acres: 10,890 sq ft is a quarter acre, 21,780 is a half. The figure is exact by definition, and it comes from 160 square rods, each rod being 16.5 feet.
An acre is an area, not a shape. Nothing about it fixes the length of any side.
square feet to acres — quick reference
| square feet (sq ft) | acres (ac) |
|---|---|
| 1,000 sq ft | 0.0230 ac |
| 5,000 sq ft | 0.1148 ac |
| 10,890 sq ft | 0.2500 ac |
| 21,780 sq ft | 0.5000 ac |
| 43,560 sq ft | 1.0000 ac |
| 87,120 sq ft | 2.0000 ac |
| 217,800 sq ft | 5.0000 ac |
| 435,600 sq ft | 10.0000 ac |
The formula, worked line by line
One division by an exact integer. The acre is 43,560 square feet by definition, so there is no constant to choose and no rounding to justify. The only judgement on this page is about what the square footage represents, which the arithmetic cannot check for you.
“An acre is a measure of area. It is not a measure of length, and it prescribes no shape.”
It matters practically. Two lots of exactly one acre can have wildly different frontages, and frontage is what determines whether a house fits, what a fence costs, and often what the land is worth. The acre figure tells you how much ground there is and nothing at all about its outline.
acres = square feet / 43,560
43,560 = 160 square rods = 160 x 16.5 x 16.5
10,890 / 43,560 = 0.25 acres
43,560 x 0.09290304 = 4,046.8564224 square metres
640 acres = 1 square mile = 27,878,400 sq ft- Lot area
- 8,500 sq ft
- Divided by 43,560
- 0.1951 acres
- Rounded to two places
- 0.20 acres
- What those two places hide
- 212 sq ft
- Acres
- 0.1951 ac
Two decimals is fine for conversation and wrong for a document. On a small lot the third and fourth decimal places are hundreds of square feet, which is the difference between a permitted extension and a refused one.
Square feet of what, exactly
Lot area is the land. Gross building area includes everything under roof. Living area excludes garages and unfinished space, and its definition varies by market. Only lot area converts meaningfully to acres, and a listing that gives a single square-foot figure usually means the building.
Scale anchors that are actually true
- Tackle football field, with end zones
- 57,600 sq ft = 1.32 acres
- The same field, between the goal lines
- 48,000 sq ft = 1.10 acres
- Doubles tennis court, playing area
- 2,808 sq ft = 0.064 acres
- One acre as a square
- about 208.71 ft a side
- One section, US land survey
- 640 acres = 1 square mile
Every row here is a published dimension multiplied out, not an impression. The tennis figure covers the playing rectangle only and excludes the run-off around it.
The section is worth knowing if you ever read a legal description in the western United States. Land there is described by township, range and section, and a section is one square mile of 640 acres, quartered and quartered again down to the 40-acre parcel that gave the phrase "back forty" its name.
How to use the square feet to acres converter
An acre is 43,560 square feet exactly. Divide and you have your answer, and because the factor is a definition rather than a measurement there is no tolerance hiding in it. What causes trouble on this conversion is never the arithmetic; it is what the square footage was measuring in the first place.
Property listings quote at least three different square-foot figures and rarely label them clearly. Lot area is the land. Gross building area is the structure. Living area excludes garages, unfinished basements and often anything with a low ceiling. Converting the wrong one to acres produces a number that is arithmetically perfect and describes nothing.
43,560
Square feet in an acre
exactly, by definition
10,890
A quarter acre
the common lot fraction
4,046.86
Square metres in an acre
4,046.8564224 exactly
The metric figure follows from the same 1959 agreement that fixed the foot. A foot is exactly 0.3048 m, so a square foot is exactly 0.09290304 square metres, and 43,560 of them is exactly 4,046.8564224 square metres. Every digit of that is derived rather than measured, which is why it can be quoted to ten places without hedging.
That comparison is worth getting right because it is the one everybody reaches for. The playing field between the goal lines is 300 by 160 feet, or 48,000 sq ft, which is 1.10 acres — still not an acre. There is no part of a football field that is conveniently one acre, and pages that say otherwise are repeating each other.
- 1/10 acre
- 4,356 sq ft
- 1/8 acre
- 5,445 sq ft
- 1/4 acre
- 10,890 sq ft
- 1/3 acre
- 14,520 sq ft
- 1/2 acre
- 21,780 sq ft
- 1 acre
- 43,560 sq ft
These are the fractions zoning codes and listings actually use. Each is exact, since 43,560 divides cleanly by 10, 8, 4, 3 and 2.
Convert the same land into hectares
Outside the United States land is measured in hectares, and the two do not line up neatly. That page runs the conversion and shows the exact figure behind it.
Open the acres to hectares converter →Square feet converted to acres at the exact 43,560 factor, with what each size corresponds to in practice.
| Square feet | Acres | What it is |
|---|---|---|
| 1,000 sq ft | 0.0230 ac | |
| 2,500 sq ft | 0.0574 ac | |
| 4,356 sq ft | 0.1000 ac | a tenth of an acre |
| 5,000 sq ft | 0.1148 ac | |
| 5,445 sq ft | 0.1250 ac | an eighth |
| 7,500 sq ft | 0.1722 ac | |
| 10,890 sq ft | 0.2500 ac | a quarter acre |
| 14,520 sq ft | 0.3333 ac | a third |
| 21,780 sq ft | 0.5000 ac | a half acre |
| 43,560 sq ft | 1.0000 ac | one acre |
| 57,600 sq ft | 1.3223 ac | a football field with end zones |
| 87,120 sq ft | 2.0000 ac | |
| 435,600 sq ft | 10.0000 ac |
Where 43,560 comes from
The number looks arbitrary and is not. It descends from the rod, a surveying length of 16.5 feet, and from the medieval acre described as forty perches long by four wide. Forty by four is 160 square rods, and 160 times 16.5 squared is 43,560 square feet exactly.
- 1 rod
- 16.5 feet
- 4 rods
- 1 chain, 66 feet
- 40 rods
- 1 furlong, 660 feet
- 1 chain by 1 furlong
- 66 x 660 = 43,560 sq ft
- One acre
- 43,560 square feet
Worth stating carefully: 66 by 660 feet is an area equal to an acre, not the acre's definition. The acre is older than Gunter's chain, which arrived in 1620, so the chain is a convenient way to lay one out rather than the reason for the number.
The agricultural story behind it — an acre as the land a team could plough in a day — is real but should not be oversold. What a day's ploughing covered varied with soil, animals and weather. The modern acre is an exact area that inherited an old name, not a measure of anyone's productivity.
An acre has no shape, and the survey acre is gone
The single most repeated error about this unit is giving it dimensions. An acre is an area. It can be a long strip, an L, or a circle. A square acre has sides of about 208.71 feet, and the familiar "209 feet" is that figure rounded to whole feet — fine as an approximation, wrong if read as exact, since 209 squared is 43,681 square feet.
Do
- Treat the acre purely as an area figure
- State whether a square footage is lot area or building area
- Use four decimal places on lots under half an acre
- Use 43,560 exactly rather than a rounded 43,500
Don't
- Quote an acre as any particular number of feet on a side
- Use a football field as a one-acre comparison
- Assume a listing's square footage refers to the land
- Apply the old survey-foot acre to any new measurement
There used to be a second acre. The US survey foot was slightly longer than the international foot, which made a survey acre about four parts per million larger — roughly 0.016 square metres. It was deprecated at the end of 2022, and since 1 January 2023 survey-foot definitions are for legacy work only. For anything measured today there is one acre.
Every square feet value, worked out
51 common square feet figures each get their own page, with the answer at full precision, the arithmetic, what rounding costs, and the nearest real-world reference point on the scale.
100 to 999 sq ft
1,000 and up sq ft
Questions people ask
Sources
Where the constants and formulas on this page come from. Each line names the figure it backs.
One acre is exactly 43,560 square feet and exactly 4,046.8564224 square metres, following from the international foot of 0.3048 metres.
US Survey Foot — Revised Unit Conversion Factors — National Institute of Standards and Technology
Survey-foot definitions, and therefore the survey acre, have been deprecated for new work since 1 January 2023.
US Survey Foot — Frequently Asked Questions — National Institute of Standards and Technology
The playing field is 360 feet long including both end zones and 160 feet wide, giving 57,600 square feet.
Official Playing Rules of the National Football League — National Football League
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