Inches to Centimetres Calculator — in to cm
One inch is exactly 2.54 centimetres — a defined constant since 1959. Enter any length in inches to get centimetres, millimetres and metres instantly.
in
1 inch = 2.54 cm (exact, by definition)
- 1
Conversion factor
2.541 inch = 2.54 cm — an exact defined constant since the 1959 international agreement. - 2
Centimetres
12 × 2.54 = 30.4800
How does this calculator work?
Multiply inches by 2.54 to get centimetres — this is exact by international definition. For millimetres multiply by 25.4; for metres multiply by 0.0254. Example: 12 inches = 30.48 cm.
Formula
How this is calculated
The inch-to-centimetre conversion is exact: one international inch is defined as 2.54 centimetres. This has been the legal definition in both the United States and the United Kingdom since 1 July 1959, so there is no measurement uncertainty — the conversion factor is a mathematical constant, not an approximation.
Multiply the number of inches by 2.54 to get centimetres. For millimetres, multiply by 25.4 (since 1 cm = 10 mm). For metres, divide centimetres by 100. The "feet and inches" breakdown uses integer division: whole feet = ⌊inches / 12⌋ with the remainder expressed as fractional inches.
This calculator accepts decimal inch values (e.g. 5.5 inches = 13.97 cm) and is useful for conversions between US customary / imperial measurements and the metric system used in most of the world.
Frequently asked questions
Exactly 2.54 centimetres. This is the international standard definition of the inch, set in 1959, and is exact — not a rounded approximation.
First convert the total length to inches: 5 × 12 + 11 = 71 inches. Then multiply by 2.54: 71 × 2.54 = 180.34 cm.
A centimetre is a metric unit equal to 1/100 of a metre. An inch is an imperial/US customary unit. One inch is 2.54 cm, so a centimetre is about 0.394 inches — just under half an inch.
Also known as
TG we-Calculate Editorial Team. (2026). Inches to Centimetres Calculator — in to cm [Online calculator]. TG we-Calculate. https://we-calculate.com/calculator/in-to-cm-calculator
TG we-Calculate Editorial Team. "Inches to Centimetres Calculator — in to cm." TG we-Calculate. 2026. https://we-calculate.com/calculator/in-to-cm-calculator.
TG we-Calculate Editorial Team, "Inches to Centimetres Calculator — in to cm," TG we-Calculate, 2026. [Online]. Available: https://we-calculate.com/calculator/in-to-cm-calculator
@misc{wecalculate_in_to_cm_calculator, title = {Inches to Centimetres Calculator — in to cm}, author = {{TG we-Calculate Editorial Team}}, howpublished = {\url{https://we-calculate.com/calculator/in-to-cm-calculator}}, year = {2026}, note = {TG we-Calculate} }
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