Convert inches and centimetres instantly. This free inch to cm converter works either direction using the exact factor (1 in = 2.54 cm), and also shows millimetres and feet-and-inches.
Enter a length and choose the direction. One inch equals exactly 2.54 centimetres, so the conversion is precise (not rounded).
A quick estimate: multiply inches by 2.5 for centimetres, or centimetres by 0.4 for inches. The calculator uses the exact factor (2.54) for accurate results.
What This Inch to CM Converter Does
Convert inches to centimetres, or centimetres back to inches, using the exact internationally defined conversion factor. The result also shows the equivalent in millimetres and a feet-and-inches breakdown.
The Exact Conversion Factor
One inch is defined as exactly 2.54 centimetres – not an approximation, but an exact international standard set in 1959. This makes inch-to-cm conversion one of the few unit conversions with zero rounding error at the defining ratio.
For example, 12 inches converts to exactly 30.48 cm, which is also exactly 1 foot.
The Quick Estimate vs the Exact Figure
A common shortcut multiplies inches by 2.5 for a quick centimetres estimate. This is close enough for casual use but introduces a small error that grows with larger measurements, since the true factor is 2.54, not 2.5.
Why the 1959 Standardization Matters
Before 1959, different English-speaking countries used slightly different inch definitions for precision engineering and surveying. The International Yard and Pound Agreement fixed the inch at exactly 2.54 cm worldwide, removing that ambiguity for all modern conversions.
Reading Feet and Inches
Height and door or furniture dimensions are often expressed in feet and inches rather than inches alone, where 1 foot = 12 inches. This converter breaks an inch total down into whole feet plus remaining inches automatically.
Common Uses for This Conversion
This conversion comes up constantly when following furniture or appliance dimensions listed in a different unit than you’re used to, checking clothing or shoe size charts across regions, comparing screen or monitor sizes, reading a printed pattern or blueprint, or converting height between metric and imperial systems.
Why Millimetres Matter for Precision Work
For woodworking, machining, and other precision trades, centimetres alone can be too coarse a unit to work with comfortably. Converting down to millimetres gives a finer level of detail – for example, a fraction of an inch like 1/8 in converts to about 3.2 mm, a distinction that matters when a tight tolerance is required.
How to Use the Inch to CM Converter
- Choose a direction: inches to cm, or cm to inches.
- Enter your length, decimals included.
- Review the result along with the millimetres and feet-and-inches breakdown.
Converting a weight instead? See our Kg to Pounds Converter.