MM to CM Converter
Convert millimetres to centimetres — ten to the centimetre. Results update as you type; exact factors shown.
One millimetre is 0.1 centimetres — see the exact factor, not a rounded rule of thumb.
How the mm to cm converter works
Every length is converted through the metre, the SI base unit of length. The inch has been defined as exactly 25.4 mm since the 1959 international yard and pound agreement, so a foot is exactly 0.3048 m, a yard 0.9144 m and a statute mile 1,609.344 m. The nautical mile is 1,852 m by international definition.
Australia is fully metric under the National Measurement Act 1960; imperial units appear only in trade with the US and in older documents.
Common length conversions
| From | To | Units |
|---|---|---|
| 1 mm | 0.1 cm | millimetre to centimetres |
| 5 mm | 0.5 cm | millimetres to centimetres |
| 10 mm | 1 cm | millimetres to centimetres |
| 12 mm | 1.2 cm | millimetres to centimetres |
| 15 mm | 1.5 cm | millimetres to centimetres |
| 20 mm | 2 cm | millimetres to centimetres |
| 25 mm | 2.5 cm | millimetres to centimetres |
| 50 mm | 5 cm | millimetres to centimetres |
| 100 mm | 10 cm | millimetres to centimetres |
| 150 mm | 15 cm | millimetres to centimetres |
| 250 mm | 25 cm | millimetres to centimetres |
| 1,000 mm | 100 cm | millimetres to centimetres |
Units in this converter and their exact factors
| Unit | Symbol | One unit in metres |
|---|---|---|
| millimetre | mm | 0.001 metre |
| centimetre | cm | 0.01 metre |
| metre | m | 1 metre |
| kilometre | km | 1,000 metre |
| inch | in | 0.0254 metre |
| foot | ft | 0.3048 metre |
| yard | yd | 0.9144 metre |
| mile | mi | 1,609.344 metre |
| nautical mile | nmi | 1,852 metre |
FAQFrequently asked questions about length conversion
How many mm in a cm?
Ten.
What is 250 mm in cm?
25 cm.
How do I convert quickly?
Move the decimal point one place left.
Which is used on drawings?
Millimetres, because most part dimensions come out whole.
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 Measurement Institute (NMI) — Australia's national measurement authority.
Last checked: September 2026. Conversion factors are fixed by definition and do not change with tax years or regulations.