The exact factor
One inch is exactly 0.0254 metres — the same as 2.54 cm or 25.4 mm. It became an exact definition in 1959 when the international yard was fixed at 0.9144 m, so every inch-to-metre conversion is precise, not rounded. For a rough check in your head, 40 inches is about 1 metre (the exact figure is 39.37).
Common values
| Inches | Centimetres | Metres |
|---|---|---|
| 1 in | 2.54 cm | 0.0254 m |
| 12 in | 30.48 cm | 0.3048 m (1 foot) |
| 36 in | 91.44 cm | 0.9144 m (1 yard) |
| 39.37 in | 100 cm | 1.0 m |
| 60 in | 152.4 cm | 1.524 m (5 ft) |
| 72 in | 182.88 cm | 1.829 m (6 ft) |
Screen and TV sizes stay in inches worldwide: a 27-inch monitor is a 68.6 cm diagonal, a 55-inch TV is 1.40 m.
Watch the “about 2.5 cm” shortcut
- 1 inch is 25.4 mm, not 25. The 1.6% gap is invisible on one inch but adds up over a long run, so use the exact factor for anything with a tolerance.
- 1 foot is 30.48 cm, not 30. Rounding a foot to 30 cm carries the same 1.6% error into every measurement.
- An inch is not a centimetre. They differ by a factor of 2.54, a common beginner mix-up.
Common questions
How many metres is one inch?
Exactly 0.0254 metres, which is 2.54 cm or 25.4 mm. This has been an exact definition since the 1959 international agreement, not an approximation.
How do I convert inches to metres?
Multiply the number of inches by 0.0254. For example, 50 inches is 50 x 0.0254 = 1.27 metres. Going the other way, multiply metres by 39.37 to get inches.
What is 36 inches in metres?
0.9144 metres, which is exactly one yard. A yard is 36 inches, and the 1959 agreement fixed it at 0.9144 m, which is where the 0.0254 factor comes from.
