| Name | symbol | equivalence(s) in smaller units | equivalence(s) in larger units | standard equivalent |
|---|---|---|---|---|
| square quectometre or square quectometer | qm² | 0.001 rm² | 10⁻⁶⁰ m² one novemdecillionth of a square metre | |
| square rontometre or square rontometer | rm² | 1,000,000 qm² | 0.000001 ym² | 10⁻⁵⁴ m² one septendecillionth of a square metre |
| square yoctometre or square yoctometer | ym² | 1,000,000 rm² | 0.000001 zm² | 10⁻⁴⁸ m² one quindecillionth of a square metre |
| square zeptometre or square zeptometer | zm² | 1,000,000 ym² | 0.000001 am² | 10⁻⁴² m² one tredecillionth of a square metre |
| attometre square or attometer | am² | 1,000,000 zm² | 0.000001 fm² | 10⁻³⁶ m² one undecillionth of a square metre |
| square femtometre or square femtometer | fm² | 1,000,000 am² | 0.000001 pm² | 10⁻³⁰ m² one nonillionth of a square metre |
| barn | 100 fm² | 0.0001 pm² | 10⁻²⁸ m² ten octillionths of a square metre | |
| square picometre or square picometer | pm² | 1,000,000 fm² | 0.000001 nm² | 10⁻²⁴ m² one septillionth of a square metre |
| square nanometre or square nanometer | nm² | 1,000,000 pm² | 0.000001 µm² | 10⁻¹⁸ m² one quintillionth of a square metre |
| square micrometre or square micron | µm² | 1,000,000 nm² | 0.000001 mm | 10⁻¹² m one trillionth of a square metre |
| square mil | sq. mil | ¹⁄₁₀₀₀₀₀₀ sq. in. | 645.16 µm² | |
| square millimetre or square millimeter | mm² | 1,000,000 µm | 0.01 cm | 0.000001 m = 10⁻⁶ m one millionth of a square metre |
| square centimetre or square centimeter | cm² | 10 mm | 0.1 dm | 0.01 m = 10⁻⁴ m one ten thousandth of a square metre |
| square inch | sq. in. | ¹⁄₁₄₄ square foot ¹∕₁₂₉₆ square yard | 6.4516 cm² 645.16 mm² | |
| square decimetre or square decimeter | dm | 100 cm² | 0.01 m | 0.01 m = 10⁻² m one hundredth of a square metre |
| square foot | sq. ft. | 144 square inches | ¹⁄₉ square yard | 929.0304 cm² |
| square yard | sq. yd. | 1,296 square inches | 9 square feet | 8,361.2736 cm² |
| square metre or square meter | m² | 1,000,000 mm² 10,000 cm² 100 dm² | 0.01 dam² 0.0001 hm² 0.000001 km² | base unit |
| square rod | 30¼ square yards 272¼ square feet | 25.928464 m² | ||
| are or square decametre | a or dam² | 100 m² | 0.0001 km² 0.01 ha | 100 m² one hundred square metres |
| square chain | 16 square rods 4,356 square feet | ¹⁄₁₀ acre ¹⁄₆₄₀₀ square mile | 404.68564224 m² | |
| acre | ac. | 10 square chains 160 square rods 4,840 square yards 43,560 square feet | ¹⁄₆₄₀ section about 0.405 ha | 4,046.8564224 m² |
| hectare or square hectometre | ha or hm² | 10,000 m² 100 ares about 2½ acres | 0.01 km² | 10,000 m² ten thousand square metres |
| square kilometre or square kilometer | km² | 1,000,000 m | 0.000001 Mm² | 10⁶ m one million square metres |
| square mile or section | sq. mi. | 27,878,400 square feet 640 acres about 259 ha | ¹⁄₃₆ township | 2,589,988.110336 m² |
| township | twp. | 36 sections 23,040 acres | 93.239571972096 km² | |
| square megametre
or square megameter | Mm² | 1,000,000 km² | 0.000001 Gm² | 10¹² m² one trillion square metres |
| square gigametre
or square gigameter | Gm² | 1,000,000 Mm² | 0.000001 Tm² | 10¹⁸ m² one quintillion square metres |
| square terametre
or square terameter | Tm² | 1,000,000 Gm² | 0.000001 Pm² | 10²⁴ m² one septillion square metres |
| square petametre
or square petameter | Pm² | 1,000,000 Tm² | 0.000001 Em² | 10³⁰ m² one nonillion square metres |
| square exametre
or square exameter | Em² | 1,000,000 Pm² | 0.000001 Zm² | 10³⁶ m² one undecillion square metres |
| square zettametre
or square zettameter | Zm² | 1,000,000 Em² | 0.000001 Ym² | 10⁴² m² one tredecillion square metres |
| square yottametre
or square yottameter | Ym² | 1,000,000 Zm² | 0.000001 Rm² | 10⁴⁸ m² one quindecillion square metres |
| square ronnametre
or square ronnameter | Rm² | 1,000,000 Ym² | 0.000001 Qm² | 10⁵⁴ m² one septendecillion square metres |
| square quettametre
or square quettameter | Qm² | 1,000,000 Rm² | 10⁶⁰ m² one novemdecillion square metres |
In measuring area, you may hear both the expressions like "four square metre" and "four metres square". These two phrases have different meanings: as a matter of fact, "four metres square" is the same as "sixteen square metres". When we say "square metre", "square foot", or "square" followed by another length, we are talking about the unit of area equal to a square with all sides equal to one metre, foot, or whatever other unit is being used, and any quantity refers to the count of squares of that size. When we say so many "metres squared", we are talking about the area of a square whose sides are so many metres, so "four metres squared" is (4 m) ² or 16 m², but "four square metres" is 4 (m²) which we write 4 m².
Geometry and calculus provide us with many formulæ for calculating the area of shapes besides squares, so we can calculate the area of a circle with a four-metre diameter as using r = d/2 and a = 𝜋·r², so for d = 4 m, we find the radius r = (4 m) ÷ 2 = 2 m, and the area a = 𝜋 × (2 m)² = 𝜋 × (4 m²) ≈ 3.14 × 4 m² ≈ 12.6 m² (approximately twelve and six tenths square metres).