Area Converter

How it works

An area unit is the square of a length unit, so its size follows from the length definitions. Since the 1959 international yard and pound agreement one foot is exactly 0.3048 m, which makes one square foot exactly 0.09290304 m², one square inch exactly 6.4516 cm² and one square yard exactly 0.83612736 m². An acre is 43,560 square feet, so it is exactly 4,046.8564224 m², and a square mile is 640 acres. A hectare is 10,000 m² and a square kilometre is 100 hectares.

The calculator multiplies your value by the size of the from unit in square metres, then divides by the size of the to unit. The factor shown is what one from unit equals in the to unit.

Conversions within one system come out as whole numbers (144 square inches to the square foot, 9 square feet to the square yard, 43,560 square feet to the acre). Metric-to-customary conversions are exact decimals or their reciprocals. Results are rounded to six decimal places for display only.

Formula

square metres = value × m² per from unit
result        = square metres ÷ m² per to unit
factor        = m² per from unit ÷ m² per to unit
1 sq ft = 0.3048² m² = 0.09290304 m²   1 acre = 43,560 sq ft = 4,046.8564224 m²   1 sq mi = 640 acres
1 ha = 10,000 m²   1 km² = 100 ha

Example

The default, 1 acre to square feet: 4,046.8564224 m² ÷ 0.09290304 m² = 43,560 sq ft. The factor is 43,560 sq ft per acre.

1 hectare to acres is 10,000 ÷ 4,046.8564224 = 2.471054 acres. A 2,000 sq ft floor is 2,000 × 0.09290304 = 185.806080 m². 1 square mile is 640 acres, or 640 × 4,046.8564224 m² = 2.589988 km².

Assumptions and limitations

• Units use the exact legal definitions: the 1959 international yard and pound agreement (1 ft = 0.3048 m), the acre of 43,560 sq ft (NIST Handbook 44, Appendix C) and the SI (hectare = 10,000 m², SI Brochure Table 8).
• The acre, square mile and square foot are the international versions. Areas recorded in US survey feet differ by about 4 parts per million.
• A negative value converts with its sign kept, so a change in area can be converted as well as an area.
• Results are rounded to six decimal places for display; the arithmetic is done in full double precision.

Frequently asked questions