Square Millimetres to Square Centimetres Converter
Convert square millimetres to square centimetres — divide by 100, not by 10. Results update as you type; exact factors shown.
One square millimetre is 0.01 square centimetres — see the exact factor, not a rounded rule of thumb.
How the square millimetres to square centimetres converter works
Areas convert through the square metre. Because the inch is exactly 25.4 mm, a square foot is exactly 0.09290304 m², an acre (43,560 square feet) is exactly 4,046.8564224 m² and a square mile (640 acres) is 2,589,988.110336 m². A hectare is 10,000 m² by definition.
The UK is metric for most trade and science but keeps miles, pints, stone and mpg (with the imperial gallon) in daily life.
Common area conversions
| From | To | Units |
|---|---|---|
| 10 mm² | 0.1 cm² | square millimetres to square centimetres |
| 50 mm² | 0.5 cm² | square millimetres to square centimetres |
| 100 mm² | 1 cm² | square millimetres to square centimetres |
| 250 mm² | 2.5 cm² | square millimetres to square centimetres |
| 500 mm² | 5 cm² | square millimetres to square centimetres |
| 1,000 mm² | 10 cm² | square millimetres to square centimetres |
| 2,500 mm² | 25 cm² | square millimetres to square centimetres |
| 5,000 mm² | 50 cm² | square millimetres to square centimetres |
| 10,000 mm² | 100 cm² | square millimetres to square centimetres |
| 25,000 mm² | 250 cm² | square millimetres to square centimetres |
| 50,000 mm² | 500 cm² | square millimetres to square centimetres |
| 100,000 mm² | 1,000 cm² | square millimetres to square centimetres |
Units in this converter and their exact factors
| Unit | Symbol | One unit in square metres |
|---|---|---|
| square millimetre | mm² | 0.000001 square metre |
| square centimetre | cm² | 0.0001 square metre |
| square metre | m² | 1 square metre |
| hectare | ha | 10,000 square metre |
| square kilometre | km² | 1,000,000 square metre |
| square inch | in² | 0.00064516 square metre |
| square foot | ft² | 0.09290304 square metre |
| square yard | yd² | 0.83612736 square metre |
| acre | ac | 4,046.8564224 square metre |
| square mile | mi² | 2,589,988.110336 square metre |
FAQFrequently asked questions about area conversion
How many square millimetres in a square centimetre?
Exactly 100.
Why 100 and not 10?
Because area is squared: ten millimetres each way gives 10 × 10 = 100 mm².
What is 500 mm² in cm²?
5 cm².
Where is mm² used?
Cable cross-sections, machining tolerances and anything specified on an engineering drawing.
What is 1 cm² in mm²?
100 mm².
Where these figures come from
- BIPM — The International System of Units (SI Brochure, 9th edition) — definitions of the base and derived units.
- NIST Special Publication 811 — Guide for the Use of the International System of Units — the exact conversion factors used here.
- National Physical Laboratory (NPL) — United Kingdom's national measurement authority.
Last checked: September 2026. Conversion factors are fixed by definition and do not change with tax years or regulations.