Length
Inches to centimetres
A single multiplication. The factor is exact by definition, so it never contributes error of its own.
The Formula
cm = in x 2.54
A single multiplication. The factor is exact by definition, so it never contributes error of its own.
| Symbol | Meaning | Unit | Notes |
|---|---|---|---|
| in | Length in inches | inches | Collapse feet-and-inches measurements into one number of inches first. |
| 2.54 | Centimetres per inch | cm per inch | Defined exactly in 1959, not a measured or rounded value. |
| cm | Length in centimetres | centimetres | Always larger than the inch count, which is the fastest sanity check. |
What Each Symbol Means
ininches
Length in inches
Collapse feet-and-inches measurements into one number of inches first.
2.54cm per inch
Centimetres per inch
Defined exactly in 1959, not a measured or rounded value.
cmcentimetres
Length in centimetres
Always larger than the inch count, which is the fastest sanity check.
See It Worked With Real Numbers
A formula on its own does not tell you which number goes where. The how to convert inches to centimeters page applies this equation to a concrete case, shows every intermediate step, and names the mistakes that produce a wrong answer even when the algebra is right.
Where This Formula Appears
This equation is the working core of How To Convert Inches To Centimeters, filed under Unit Conversion. Every number the guide produces comes from substituting into this one line.