An area unit conversion comes up constantly once you’ve calculated an area: a floor plan in square feet needs to become square meters for an international contractor, a land survey in acres needs to become hectares for a metric spreadsheet, or a small lab measurement in square inches needs to become square centimeters. This calculator converts one area value into ten common units at once — square millimeters, square centimeters, square meters, square kilometers, square inches, square feet, square yards, acres, hectares, and square miles — so you only have to enter a value once.
Every conversion factor below comes from the exact, internationally defined relationships between these units (the inch, foot, and yard have been defined as exact fractions of a meter since 1959), cross-checked against NIST’s own published conversion tables, rather than rounded approximations picked up from a random source.
How Area Unit Conversion Works
Converted Value = Original Value × (Original Unit’s Square-Meter Factor ÷ Target Unit’s Square-Meter Factor)
Every unit below has an exact, fixed relationship to the square meter, so converting between any two of them is really just converting each one to square meters and back out to the other unit.
Metric Area Units
Square millimeters, square centimeters, square meters, and square kilometers scale by powers of ten, since the meter itself scales that way: 1 square centimeter = 100 square millimeters, 1 square meter = 10,000 square centimeters, and 1 square kilometer = 1,000,000 square meters.
Worked Example
A 25-square-meter room: 25 × 10,000 = 250,000 square centimeters, or 25 ÷ 1,000,000 = 0.000025 square kilometers.
U.S. Customary / Imperial Area Units
Square inches, square feet, and square yards are related by the same 12-inches-per-foot and 3-feet-per-yard relationships used for length: 1 square foot = 144 square inches, and 1 square yard = 9 square feet.
Worked Example
A 1,500-square-foot house: 1,500 ÷ 9 = 166.67 square yards, or 1,500 × 144 = 216,000 square inches.
Land Area Units: Acres and Hectares
An acre is defined as exactly 4,840 square yards (equivalently, 43,560 square feet). A hectare is defined as exactly 10,000 square meters. These two units come from different measurement systems, so converting between them requires the square-meter conversion in between — there’s no simple whole-number ratio.
Worked Example
A 5-acre lot: 5 × 4,046.8564224 = 20,234.28 square meters, or 20,234.28 ÷ 10,000 = 2.02 hectares. One hectare is about 2.47 acres.
Square Miles and Square Kilometers
A square mile is defined as exactly 640 acres. Converting a square mile to square kilometers uses the same square-meter conversion path as any other cross-system conversion.
Worked Example
A 3-square-mile area: 3 × 640 = 1,920 acres, or 3 × 2.589988 ≈ 7.77 square kilometers.
Why These Conversion Factors Aren’t Rounded Guesses
Some area unit converters quietly round their conversion factors, which can throw off results at larger scales (a rounding error that’s invisible on 1 square foot becomes a real discrepancy on a 500-acre survey). The factors used here are exact wherever the underlying unit definitions are exact — 1 inch = 0.0254 meters, 1 foot = 0.3048 meters, and 1 yard = 0.9144 meters are all exact by international agreement — and are cross-verified two ways: by deriving them directly from those base-unit definitions, and separately from the exact whole-number relationships between units (4,840 square yards per acre, 640 acres per square mile, 10,000 square meters per hectare). Both derivation paths agree to well beyond the precision most projects need.
A Note on Acres: International Foot vs. U.S. Survey Foot
There is one small historical wrinkle worth knowing about: older U.S. land surveys sometimes used the “U.S. survey foot,” a slightly different (and now retired) definition of the foot that made an acre equal to about 4,046.873 square meters instead of the 4,046.8564 square meters used here (based on the modern international foot). The difference is tiny — about 17 parts per million — and won’t matter for virtually any everyday conversion, but it can matter on very large, legally recorded survey boundaries, where the original survey’s foot definition is what legally controls.
Frequently Asked Questions
How do I convert square feet to square meters?
Multiply the square-foot value by 0.09290304 (an exact conversion, since 1 foot = 0.3048 meters exactly). For example, 1,000 square feet × 0.09290304 ≈ 92.9 square meters.
How many square feet are in an acre?
Exactly 43,560 square feet, by definition — this is one of the exact whole-number relationships used to derive the conversion factors on this page.
Is a hectare bigger than an acre?
Yes. One hectare (10,000 square meters) equals about 2.47 acres, so a hectare is roughly two and a half times the size of an acre.
Why do some converters give slightly different results for acres?
Most of the time it’s the international-foot vs. U.S.-survey-foot distinction described above — a difference of about 17 parts per million, which shows up only at large scales or in legally recorded survey measurements.
What’s the difference between a square mile and a section?
In the U.S. Public Land Survey System, a “section” is defined as one square mile (640 acres), so the two terms refer to the same area — “section” is just the surveying term for it.
Can I convert more than one value at a time?
Enter one value and unit, and the calculator shows that value converted into all ten supported units simultaneously, so you can read off whichever ones you need.