Area Converter Guide: Square Meters, Square Feet, Acres, Hectares, Square Miles, and More
Area conversion changes the unit used to describe a two-dimensional quantity without changing the actual size of the surface.
The SI unit of area is the square meter, written m². NIST describes area as a two-dimensional quantity measured in square units and identifies the square meter as the SI derived unit of area.
Area conversions differ fundamentally from ordinary length conversions because the length conversion factor must be squared.
For example, one foot equals exactly 0.3048 meter under the international-foot definition. A square foot therefore equals 0.3048 × 0.3048 square meter, or exactly 0.09290304 m².
This is why converting 100 square feet to square meters is not done by multiplying by 0.3048. The correct factor is 0.09290304, producing 9.290304 m².
Metric area units follow the same principle. One meter equals 100 centimeters, so one square meter equals 100² = 10,000 square centimeters.
NIST also notes a convenient metric-area progression: 100 mm² = 1 cm², 100 cm² = 1 dm², 100 dm² = 1 m², 100 m² = 1 are, 100 ares = 1 hectare, and 100 hectares = 1 km².
The hectare is widely used for land area. The current SI Brochure identifies the hectare as a unit accepted for use with the SI and defines 1 hectare as exactly 10,000 m².
U.S. customary area units are also widely used in property, construction, and land measurement. With the international foot, 1 square inch equals exactly 0.00064516 m², 1 square foot equals exactly 0.09290304 m², 1 square yard equals exactly 0.83612736 m², and 1 square mile equals exactly 2,589,988.110336 m².
An acre based on the international foot contains 43,560 square feet and equals exactly 4,046.8564224 m². This is the modern conversion that should normally be used for general-purpose area conversion in the United States.
Historical U.S. surveying introduces an important precision distinction. The U.S. survey foot was slightly longer than the international foot, so a survey-foot-based acre and square mile are also slightly larger.
NIST states that use of the U.S. survey foot was discontinued after December 31, 2022 except for historical and legacy applications. Modern general-purpose conversion should therefore default to international-foot-based units while optionally allowing legacy survey units where needed.
This calculator focuses only on unit conversion. If the area itself must first be calculated from geometric dimensions, use the Area and Perimeter Calculator.
How to Convert Area Units Correctly
- Enter the area value: Enter a nonnegative area for ordinary physical-area conversion. Signed values can be accepted mathematically if the application has a specific use for them.
- Choose the source unit: Select the unit currently attached to the area value.
- Choose the target unit: Select the area unit you want to convert into.
- Use standard international-foot units by default: For square feet, square yards, acres, and square miles, use modern international-foot-based definitions unless a legacy survey unit is explicitly requested.
- Review the conversion factor: Display the factor used so the conversion can be independently checked.
- Preserve adequate precision: Carry full conversion precision internally and round only the displayed result according to the user’s needs.
- Use geometry first when area is unknown: If only dimensions are available, calculate the area with the Area and Perimeter Calculator before converting units.
Formula and variables
Area is two-dimensional, so converting each length dimension multiplies the scale factor twice. If 1 source length unit equals k target length units, then 1 source square unit equals k² target square units. For named land units such as hectares or acres, the calculator can use their published direct area factors.
Converted Area = Original Area × (Length Conversion Factor)²; equivalently, Converted Area = Original Area × Area Conversion Factor- A₁ — Original area
- The numerical area expressed in the source unit.
- A₂ — Converted area
- The same physical area expressed in the target unit.
- k — Length conversion factor
- The number of target length units equivalent to one source length unit.
- k² — Area conversion factor
- The squared length conversion factor used for corresponding square units.
Scenario 1: Convert 1,500 Square Feet to Square Meters
A house has 1,500 square feet of floor area and the user wants the equivalent in square meters.
- Area
- 1,500 ft²
- Conversion factor
- 1 ft² = 0.09290304 m²
- Multiply 1,500 by 0.09290304.
- 1,500 × 0.09290304 = 139.35456.
Result: 1,500 ft² = 139.35456 m².
The conversion factor is the square of the exact international-foot length conversion: 0.3048² = 0.09290304.
Understanding your results
Converted area
This is the same physical surface expressed in the target unit.
The conversion does not change the actual size of the property or shape.
Conversion factor
This shows how many target square units correspond to one source square unit.
It can be derived by squaring the corresponding length factor for ordinary square units.
Metric land area
Hectares and square kilometers are convenient for larger land areas.
One hectare equals exactly 10,000 m².
U.S. customary land area
Acres and square miles remain common in U.S. land measurement.
The default should use international-foot-based modern values.
Legacy survey result
If a legacy survey-foot unit is selected, the result will differ slightly from modern international-foot-based conversion.
The selected basis should always be labeled clearly.
Assumptions
- The target and source units are both units of area.
- Modern U.S. customary calculations use the international foot unless a survey-foot unit is explicitly selected.
- International foot equals exactly 0.3048 meter.
- One hectare equals exactly 10,000 square meters.
- Area conversions use full internal precision before output rounding.
- No geometric recalculation is performed because the input is already an area.
Limitations
- Area conversion does not determine area from length, width, radius, or other shape dimensions.
- Converting square units with a linear conversion factor instead of its square produces an incorrect result.
- Survey-foot-based legacy area units differ slightly from international-foot-based units.
- NIST states that use of the U.S. survey foot should be avoided after December 31, 2022 except for historical and legacy applications.
- Property records can use jurisdiction-specific surveying definitions, historical datums, legal descriptions, or recorded acreages that should not be replaced by a generic converter when legal precision is required.
- Rounding can produce apparent discrepancies when converting back and forth between units.
- Very large or very small area values can require scientific notation or arbitrary-precision handling.
- The calculator does not convert volume, length, or second moment of area even when those quantities contain superficially similar squared or higher-power units.
Common mistakes
- Using a length conversion factor for an area conversion.
- Assuming 1 m² = 100 cm².
- Assuming 1 ft² = 12 in².
- Confusing square feet with feet.
- Confusing square meters with meters.
- Confusing hectares with square kilometers.
- Assuming one hectare equals one acre.
- Using survey-foot acreage without realizing it differs from international-foot acreage.
- Rounding conversion factors too early.
- Converting dimensions and then also applying an area conversion factor, effectively converting twice.
Practical use cases
Scenario 2: Square meters to square feet
Convert 100 m².
Using 1 m² ≈ 10.7639104167 ft² gives approximately 1,076.391 ft².
Scenario 3: Acres to hectares
Convert 10 international acres.
10 × 4,046.8564224 m² ÷ 10,000 ≈ 4.0468564224 ha.
Scenario 4: Hectares to square meters
Convert 2.5 ha.
2.5 × 10,000 = 25,000 m².
Scenario 5: Square miles to square kilometers
Convert 3 mi².
Using the international-foot value gives approximately 7.769964331 km².
Scenario 6: Square yards to square feet
One yard equals three feet.
Therefore 1 yd² = 3² = 9 ft².
Planning and decision guide
The square meter is the SI unit of area
NIST identifies square meter, m², as the SI derived unit for area.
Other metric area units scale from the meter using squared SI prefixes.
Scenario 7: Why one square meter contains 10,000 square centimeters
1 meter = 100 centimeters.
A 1 m by 1 m square therefore measures 100 cm by 100 cm.
100 × 100 = 10,000 cm².
Metric area factors grow by powers of 100 between adjacent decimal length prefixes
A tenfold length change becomes a hundredfold area change.
This is why moving one prefix step such as centimeter to decimeter changes square units by a factor of 100 rather than 10.
Scenario 8: cm² to m²
1 cm = 0.01 m.
Therefore 1 cm² = 0.0001 m².
Square millimeter
1 mm² = 10⁻6 m².
One million square millimeters therefore equal one square meter.
Square centimeter
1 cm² = 10⁻4 m².
10,000 cm² = 1 m².
Square decimeter
1 dm² = 0.01 m².
100 dm² = 1 m².
Are
One are equals 100 m².
It is the historical decimal land-area step directly below the hectare.
Hectare
The current SI Brochure states 1 ha = 1 hm² = 10⁴ m².
The hectare is accepted for use with the SI and is widely used for land measurement.
Scenario 9: Hectare dimensions
A square 100 m by 100 m has area 10,000 m².
That area is exactly one hectare.
Square kilometer
1 km² = 1,000² m².
Therefore 1 km² = 1,000,000 m² = 100 ha.
Scenario 10: 250 hectares to square kilometers
100 ha = 1 km².
250 ha = 2.5 km².
International inch is defined from the meter
One international inch equals exactly 0.0254 m.
Squaring gives 1 in² = exactly 0.00064516 m².
Scenario 11: Square inches to square centimeters
1 inch = 2.54 cm exactly.
1 in² = 2.54² = 6.4516 cm² exactly.
International square foot is exact relative to the meter
One international foot equals exactly 0.3048 m.
NIST gives 1 ft² = exactly 0.09290304 m².
Scenario 12: Why one square foot contains 144 square inches
1 ft = 12 in.
1 ft² = 12 × 12 = 144 in².
Square yard is nine square feet
One yard equals three feet.
Squaring the relationship gives 1 yd² = 9 ft².
Square yard metric value
NIST gives 1 yd² = exactly 0.83612736 m² for international-foot-based units.
The conversion derives from 0.9144².
Acre contains 43,560 square feet
Under the international-foot basis, 1 acre = 43,560 ft².
NIST gives the exact metric equivalent as 4,046.8564224 m².
Scenario 13: Acre to square feet
2 acres = 2 × 43,560.
Result = 87,120 ft².
Acre to hectare conversion
Divide the international-acre metric area by 10,000.
1 acre ≈ 0.40468564224 ha.
Hectare to acre conversion
The reciprocal gives approximately 2.4710538147 international acres per hectare.
This is why hectares are a little under two and one-half acres.
Scenario 14: 5 hectares to acres
5 × 2.4710538147 ≈ 12.355269 acres.
Carry full precision internally before display rounding.
Square mile is 640 acres
A standard square mile contains 27,878,400 square feet.
Dividing by 43,560 gives exactly 640 acres under the same foot basis.
International square mile metric value
NIST gives 1 international-foot-based mi² = exactly 2,589,988.110336 m².
That equals 2.589988110336 km².
Scenario 15: 1 square mile in hectares
2,589,988.110336 m² ÷ 10,000.
Result = 258.9988110336 ha.
Square kilometer to square mile is the reciprocal relationship
1 km² is approximately 0.3861021585 international square mile.
The converter should calculate the reciprocal from the same canonical factors rather than maintain inconsistent rounded pairs.
Use one canonical base unit internally
A robust converter can map every supported unit to square meters.
Conversion from source to target becomes source → m² → target.
Recommended conversion architecture
Store one high-precision square-meter factor for each unit.
Converted value = input × sourceFactor ÷ targetFactor.
Scenario 16: Acres to square feet through the canonical base
Convert acre to m² using 4,046.8564224.
Divide by 0.09290304 m² per ft².
The exact result is 43,560 ft².
Canonical factors reduce round-trip inconsistency
Maintaining separately rounded factors for every possible source-target pair can create contradictory results.
A single canonical base makes conversion internally coherent.
The U.S. survey foot is a legacy issue
NIST explains that the U.S. survey foot differs slightly from the international foot and recommends avoiding survey-foot definitions after December 31, 2022 except for historic and legacy applications.
The distinction still matters when reproducing old survey coordinates or legal records.
Legacy survey acre is slightly larger
NIST gives a survey-foot-based acre as approximately 4,046.872609874 m².
The international-foot acre is exactly 4,046.8564224 m².
Scenario 17: Difference between acre definitions
The difference is only about 0.0162 m² per acre.
That is negligible for many consumer uses but can matter across large legacy survey datasets.
Legacy survey square mile also differs
NIST gives approximately 2,589,998.470319521 m² for a survey-foot-based square mile.
The international-foot value is 2,589,988.110336 m².
Do not call the legacy survey value the ordinary modern acre
Default consumer results should use international-foot-based units.
Legacy survey units should be separately labeled, for example “acre (U.S. survey foot legacy).”
Area conversion is not perimeter conversion
Perimeter is a length and uses a first-power conversion factor.
Area uses the square of that factor.
Scenario 18: 10 ft perimeter versus 10 ft² area
10 ft converts to 3.048 m.
10 ft² converts to 0.9290304 m².
The same numerical input requires a different dimensional conversion.
Area conversion is also not volume conversion
Volume uses cubic units and cubes the length conversion factor.
For example, 1 ft³ uses 0.3048³ rather than 0.3048².
Unit exponents encode dimensionality
m means length.
m² means area.
m³ means volume.
Scientific notation helps with extreme area scales
Microscopic and geographic areas can span many orders of magnitude.
The calculator should allow scientific notation without losing the unit.
Scenario 19: Tiny area
1 mm² = 1 × 10⁻6 m².
Scientific notation makes that scaling explicit.
Large land area can also use scientific notation
10,000 km² equals 10¹⁰ m².
Either ordinary or scientific notation can be displayed according to user preference.
Rounding should be output-specific
Construction users may want two decimal places.
Survey and scientific users may need substantially more precision.
Scenario 20: Property listing
A result of 185.80608 m² may reasonably display as 185.81 m² for consumer presentation.
The internal calculation should retain the fuller value.
Significant figures can matter more than decimal places
An input measured as 120 m² may not justify a converted result with twelve meaningful digits.
The converter can provide mathematically precise factors while leaving measurement-precision interpretation to the user.
Do not alter the source measurement while converting
Conversion expresses the same measured area in another unit.
It does not increase the accuracy of the original measurement.
Property area can differ from calculated geometric area
Recorded lot acreage may come from surveyed boundaries rather than simple rectangular dimensions.
Do not recalculate legal parcel area from rough length and width unless that geometry actually represents the parcel.
The Area and Perimeter Calculator answers the geometry question
If dimensions such as 30 ft × 40 ft are known, first calculate 1,200 ft² there.
Then use Area Converter if another area unit is needed.
Scenario 21: Room conversion workflow
Room dimensions: 15 ft × 20 ft.
Geometry gives 300 ft².
Area conversion then gives approximately 27.870912 m².
Metric prefixes should be interpreted before squaring
centi means 10⁻2 for length.
Square centimeter therefore represents (10⁻2)² = 10⁻4 square meter.
Scenario 22: Square kilometer prefix
kilo means 10³.
km² therefore represents (10³)² = 10⁶ m².
Hectare is not formed by simply squaring the prefix in the unit symbol
The hectare is a named land-area unit equal to one square hectometer.
Its symbol is ha, not hm² in ordinary land-area notation, though 1 ha = 1 hm² exactly.
Are and hectare form useful decimal land relationships
1 are = 100 m².
1 hectare = 100 ares = 10,000 m².
Scenario 23: 35 ares
35 ares = 3,500 m².
That equals 0.35 hectare.
Conversions should be reversible within rounding tolerance
Converting A to B and back to A should reproduce the original input when full internal precision is used.
Large deviations usually indicate a wrong factor or premature rounding.
Scenario 24: ft² round trip
Convert 1,000 ft² to m²: 92.90304.
Convert 92.90304 m² back using the reciprocal factor.
Result returns to 1,000 ft².
The strongest converter shows unit definitions when useful
A small expandable reference can show relationships such as 1 acre = 43,560 ft² and 1 ha = 10,000 m².
This makes the tool educational without cluttering the main conversion interface.
Frequently asked questions
How do I convert area units?
Multiply the source area by the appropriate area conversion factor, or convert through a canonical unit such as square meters.
Why do area conversion factors get squared?
Area has two length dimensions. If each length changes by factor k, the area changes numerically by k².
What is the SI unit of area?
The square meter, m². NIST identifies it as the SI derived unit of area.
How many square centimeters are in one square meter?
10,000 cm².
How many square millimeters are in one square meter?
1,000,000 mm².
How many square meters are in one hectare?
Exactly 10,000 m². The SI Brochure defines 1 ha = 1 hm² = 10⁴ m².
How many hectares are in one square kilometer?
100 hectares.
How many square feet are in one square meter?
Approximately 10.7639104167 ft².
How many square meters are in one square foot?
Exactly 0.09290304 m² for the international foot.
How many square inches are in one square foot?
144 in².
How many square feet are in one square yard?
9 ft².
How many square meters are in one square yard?
Exactly 0.83612736 m² using the international yard.
How many square feet are in one acre?
43,560 ft².
How many square meters are in one acre?
One international-foot-based acre equals exactly 4,046.8564224 m².
How many hectares are in one acre?
Approximately 0.40468564224 hectare.
How many acres are in one hectare?
Approximately 2.4710538147 international acres.
How many acres are in one square mile?
640 acres.
How many square kilometers are in one square mile?
One international square mile equals exactly 2.589988110336 km².
How many square miles are in one square kilometer?
Approximately 0.3861021585 square mile.
Is one hectare the same as one acre?
No. One hectare is about 2.471 acres.
Is one square meter equal to 100 square centimeters?
No. One meter contains 100 centimeters in each direction, so 1 m² = 10,000 cm².
Is one square foot equal to 12 square inches?
No. One foot equals 12 inches, so one square foot equals 12 × 12 = 144 square inches.
What is the difference between a square foot and a foot?
A foot measures length. A square foot measures two-dimensional area.
What is the difference between acre and square mile?
A square mile contains 640 acres.
What is the difference between an acre and a survey acre?
A legacy survey-foot-based acre is slightly larger than the modern international-foot-based acre. NIST recommends avoiding survey-foot definitions after December 31, 2022 except for historical and legacy applications.
What is a U.S. survey foot?
It is a legacy foot definition equal to exactly 1200/3937 meter, slightly longer than the international foot of exactly 0.3048 meter.
Should I use survey-foot area units today?
For ordinary new calculations, generally no. NIST says survey-foot definitions should be avoided after December 31, 2022 except in historical and legacy applications.
Can I convert a room from feet to square meters directly?
First calculate its area from the dimensions if the area is not already known, then convert the resulting square feet to square meters.
Can I convert perimeter with this calculator?
No. Perimeter is a length quantity and uses linear conversion factors.
Can I convert cubic feet with this calculator?
No. Cubic feet measure volume and require cubic conversion factors.
How do I calculate area before converting it?
Use the Area and Perimeter Calculator for rectangles, circles, triangles, polygons, and other supported shapes.
Should I round the conversion factor?
Keep the full available factor internally and round only the final displayed result.
Why does my property record differ slightly from a converter?
Recorded property areas can use survey measurements, legal descriptions, legacy units, rounding, or jurisdiction-specific records rather than a simple consumer conversion.
How accurate is an area converter?
For units with exact definitions, the conversion itself can be exact before display rounding. The accuracy of the underlying measured area is a separate issue.
Sources and review
- SI Units – Area — National Institute of Standards and Technology. Accessed 2026-09-01.
- NIST Guide to the SI, Appendix B.9 — Area Conversion Factors — National Institute of Standards and Technology. Accessed 2026-09-01.
- U.S. Survey Foot: Revised Unit Conversion Factors — National Institute of Standards and Technology. Accessed 2026-09-01.
- Handbook 44 — 2026, Appendix C: General Tables of Units of Measurement — National Institute of Standards and Technology. Accessed 2026-09-01.
- SI Brochure, 9th Edition — Units Accepted for Use With the SI — Bureau International des Poids et Mesures. Accessed 2026-09-01.
Reviewed 2026-09-01 by Dr Akawak Ejigu, DBA.