Area Unit Converter
Edit either side and the other follows. Convert freely between square metres, square centimetres, square millimetres, square kilometres, hectares, square inches, square feet, square yards, acres and square miles. The "live grid" panel below shows the value in all 10 units at once — handy whether you are reading Hong Kong floor-area listings in ft², European property in m², farmland in hectares, US land in acres, or a country/lake on a map in km² or mi².
Please enter a valid number
Live value in every unit
Factors follow the 1959 international yard-and-pound agreement (1 in = 2.54 cm exactly); hectare and acre defined per NIST SP 811.
- m² European & most international property listings
- ft² Hong Kong saleable / GFA property listings
- ha Farmland, parks, development sites
- ac US and Commonwealth land, ranches
- km² Countries, cities, lakes
- in² Camera sensors, printed material
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Formula
sqMeters = value × factor[from] result = sqMeters / factor[to] factor[ft²] = 0.092 903 04 (1959 international foot, 1 ft = 0.3048 m) factor[in²] = 0.000 645 16 (1 in = 2.54 cm) factor[yd²] = 0.836 127 36 (1 yd = 0.9144 m) factor[ha] = 10 000 (hectare = 100 m × 100 m) factor[ac] = 4 046.856 4224 (1 acre = 43 560 ft²) factor[mi²] = 2 589 988.110 336 (1 mi = 1 609.344 m)
- · 1 m² = 10 000 cm² = 1 000 000 mm²; 1 ha = 10 000 m²; 1 km² = 100 ha = 1 000 000 m².
- · 1 ft² = 0.092 903 04 m² exactly (1959 international yard-and-pound agreement); 1 m² ≈ 10.7639 ft².
- · 1 in² = 6.4516 cm² exactly; 1 yd² = 9 ft² ≈ 0.836 m².
- · 1 acre = 43 560 ft² ≈ 4 046.86 m² ≈ 0.4047 ha; 1 hectare ≈ 2.471 acres.
- · 1 mi² = 640 acres = 2.589 988 km²; 1 km² ≈ 0.386 mi².
- · Hong Kong property listings quote both Gross Floor Area (GFA) and Saleable Area (SA, mandatory since the 2013 Sales of First-hand Residential Properties Ordinance) in sq.ft; 1 m² ≈ 10.764 sq.ft.
- · Mainland China, Taiwan, Japan and Korea use m²; the US, UK and Canada quote homes in sq.ft and farmland in acres; most European agricultural land is measured in hectares.
- · Sources: NIST SP 811 (2008) Guide for the Use of the International System of Units; ISO 80000-3; HK Weights & Measures Ordinance (Cap. 68).
Frequently asked
How big is a 500 sq.ft Hong Kong flat in square metres?
1 sq.ft = 0.092 903 04 m², so 500 sq.ft ≈ 46.45 m². Some common conversions: 300 sq.ft ≈ 27.87 m², 500 sq.ft ≈ 46.45 m², 700 sq.ft ≈ 65.03 m², 1 000 sq.ft ≈ 92.90 m². Since Hong Kong's 2013 Sales of First-hand Residential Properties Ordinance, new-build listings must show the Saleable Area; the marketing-friendly Gross Floor Area can no longer be quoted alone.
What is the difference between a hectare and an acre?
Both are land units. A hectare (ha) = 10 000 m² = 100 m × 100 m — a square 100 m on a side. An acre = 43 560 sq.ft ≈ 4 046.86 m² ≈ 0.4047 ha, originally defined as the area a pair of oxen could plough in a day (a 1-furlong × 1-chain rectangle, not a perfect square). Conversion: 1 ha ≈ 2.471 ac; 1 ac ≈ 0.405 ha. European and Asian agriculture overwhelmingly use ha, while the US, UK, Canada, Australia and New Zealand still quote land and large properties in acres.
Why is 1 sq.ft not simply 0.1 sq.m?
Because feet and metres are not a clean 10:1. The 1959 international agreement fixed 1 ft = 0.3048 m exactly (so 1 in = 2.54 cm), which gives 1 ft² = 0.3048² = 0.092 903 04 m² — about 92.9 % of 0.1 m². Dividing sq.ft by 10 is a quick mental estimate; for precision multiply by 0.0929 or divide by 10.764. This calculator uses the exact factor everywhere.
Can I convert m² straight to km² or mi²?
Yes. The calculator supports any pair of the 10 supported units, including the geographic-scale km² and mi². For example, Hong Kong's 1 114 km² ≈ 430 mi²; Japan's 377 975 km² ≈ 145 936 mi²; California's 423 970 km² ≈ 163 695 mi²; the UK's 243 610 km² ≈ 94 060 mi². Internally the tool routes everything through square metres, so there is no cascading round-off.
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