One square centimetre is 100 square millimetres, because 1 cm = 10 mm and the factor is squared. Wire cross-sections and sensor areas are often quoted in mm².
How to use the Square cm to Square mm Converter
- Type the number of square centimetres into the Square centimetres field. Decimals such as 0.5 are fine.
- Read the answer in Square millimetres – it updates as you type, with no button to press.
- To convert the other way, type into Square millimetres and the square centimetres are recalculated.
- Press Copy results to copy both values with the page title, or Copy link to share this exact conversion.
This page converts only cm² ⇄ mm². Need a different unit? Use the general area converter, where you can choose any “from” and “to” unit.
How it works
Both units measure area, so they are always in the same ratio: one square centimetre equals 100 square millimetres. The calculator multiplies the number of square centimetres you type by 100 to give square millimetres, and when you type into the square millimetres field it divides by the same factor to give square centimetres. Because the ratio never changes, doubling the square centimetres always doubles the square millimetres. Results are calculated at full precision and rounded only for display (up to eight decimal places, with very large or small values shown in scientific notation).
How to convert square centimetres to square millimetres
- Write down the value in square centimetres, for example 1 cm².
- Multiply by the conversion factor 100 (because 1 square centimetre = 100 mm²).
- 1 × 100 = 100 mm².
- To go back from square millimetres to square centimetres, divide by 100 – or multiply by 0.01.
cm² to mm² conversion table
| Square centimetres | Square millimetres | Square millimetres | Square centimetres |
|---|---|---|---|
| 0.01 cm² | 1 mm² | 1 mm² | 0.01 cm² |
| 0.1 cm² | 10 mm² | 2 mm² | 0.02 cm² |
| 0.5 cm² | 50 mm² | 5 mm² | 0.05 cm² |
| 1 cm² | 100 mm² | 10 mm² | 0.1 cm² |
| 2 cm² | 200 mm² | 20 mm² | 0.2 cm² |
| 5 cm² | 500 mm² | 50 mm² | 0.5 cm² |
| 10 cm² | 1,000 mm² | 100 mm² | 1 cm² |
| 100 cm² | 10,000 mm² | 1,000 mm² | 10 cm² |
What is a square centimetre?
A square centimetre is 100 mm². It is used for small areas such as wound sizes, sensor surfaces and the cross-sections of pipes.
What is a square millimetre?
A square millimetre is a square 1 mm on each side. Electrical wire sizes in metric countries are given by their cross-section in mm², for example 1.5 mm² or 2.5 mm² cable.
Common mistakes to avoid
Converting area with a length factor (1 m = 3.28 ft, but 1 m² = 10.76 ft², not 3.28 ft²), and assuming regional land units such as marla, bigha or katha have one standard size everywhere.
Formula
1 cm² = 100 mm²1 mm² = 0.01 cm²mm² = cm² × 100Worked example
Inputs — Square centimetres: 1 cm².
Results — Square millimetres = 100 mm².
Frequently asked questions
How many mm² in a cm²?
100.
How many cm² is 2.5 mm²?
0.025 cm².
How do I convert square centimetres to square millimetres?
Multiply the number of square centimetres by 100. For example, 1 cm² × 100 = 100 mm².
How do I convert square millimetres back to square centimetres?
Divide by 100 (or multiply by 0.01), or simply type the value into the square millimetres field above.
What is 10 cm² in square millimetres?
10 cm² = 1,000 mm².
What is 100 cm² in square millimetres?
100 cm² = 10,000 mm².
Is this conversion exact?
Yes. The factor comes from the official definitions of both units (NIST and the SI), so the only difference you may see is rounding in the last displayed digit.
Can I convert to other units on this page?
This page converts only between square centimetres and square millimetres. To pick any area unit, use the general area converter linked under Related calculators.
What formula does the Square cm to Square mm Converter use?
1 cm² = 100 mm².