CM to Inches Converter
Convert centimetres to inches — 1 cm is 0.3937 in, and 2.54 cm makes exactly one inch. Results update as you type; exact factors shown.
One centimetre is 0.3937 inchs — see the exact factor, not a rounded rule of thumb.
How the cm to inches 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 cm | 0.3937 in | centimetre to inchs |
| 2 cm | 0.7874 in | centimetres to inchs |
| 5 cm | 1.9685 in | centimetres to inchs |
| 10 cm | 3.937 in | centimetres to inchs |
| 15 cm | 5.9055 in | centimetres to inchs |
| 20 cm | 7.874 in | centimetres to inchs |
| 25 cm | 9.8425 in | centimetres to inchs |
| 30 cm | 11.811 in | centimetres to inchs |
| 50 cm | 19.685 in | centimetres to inchs |
| 100 cm | 39.3701 in | centimetres to inchs |
| 150 cm | 59.0551 in | centimetres to inchs |
| 180 cm | 70.8661 in | centimetres to inchs |
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 inches is 1 cm?
0.3937 inches. The relationship is defined exactly the other way round: one inch is exactly 2.54 cm.
How do I convert cm to inches in my head?
Divide by 2.5 and take a little off — 30 cm is roughly 12 inches, and the true answer is 11.81.
How tall is 180 cm in feet and inches?
70.87 inches, which is 5 feet 10.9 inches.
Is the inch exactly 2.54 cm?
Yes, since the 1959 international yard and pound agreement. Before that the US and UK inches differed very slightly.
Why does my tape measure disagree?
Most tapes round to the nearest sixteenth of an inch, which is 0.159 cm — enough to differ from an exact conversion.
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.