1 inch = 2.54 centimeters
Convert inches to centimeters with an exact, internationally defined factor — 1 in = 2.54 cm (exact).
inches to centimeters
Computed with the exact factor · NIST SP 811
| Inch | Centimeter |
|---|---|
| 0.5 in | 1.27 cm |
| 1 in | 2.54 cm |
| 2 in | 5.08 cm |
| 3 in | 7.62 cm |
| 5 in | 12.7 cm |
| 10 in | 25.4 cm |
| 25 in | 63.5 cm |
| 50 in | 127 cm |
| 100 in | 254 cm |
Exact factor details
- Exact factor
- 1 in = 2.54 cm (exact definition)
- Significant digits
- up to 4 significant digits shown
- Data source
- NIST SP 811 — verified against official tables
Why in to cm trips people up
Length conversions between metric and US customary units. The international yard and pound agreement of 1959 defined the foot as exactly 0.3048 meters, which makes every conversion below exact rather than approximate. One inch is exactly 2.54 centimeters by international definition. A centimeter is one-hundredth of a meter — the everyday metric unit for small measurements.
Metric lengths (millimeter, centimeter, meter, kilometer) scale by powers of ten, while US customary units (inch, foot, yard, mile) relate by 12, 3, and 1,760. Because the inch is defined as exactly 2.54 centimeters, converting between the two systems never accumulates rounding error at the definition level — differences only appear in how results are displayed.
Use the quick-reference table for the amounts people actually look up, and the converter above for everything in between. Both are computed from the same factor at full precision, so the table and the converter can never disagree — there is no second, rounded copy of the data anywhere on this page.
Frequently asked questions
Is the in to cm conversion exact?
Yes. 1 in = 2.54 cm (exact) and 1 cm = 0.01 m (exact) are exact definitions, so the conversion is exact — results are rounded only for readability.
How do I convert in to cm in my head?
Multiply inches by 2.5 — 10 in is 25 cm.
Why do other sites show slightly different in to cm results?
They round at different steps. This page computes with the full-precision factor and rounds only the final displayed number, so small trailing digits can differ from sites that round earlier.