Convert centimetres to inches

Formula: in = cm × 0.393701

cm to in quick reference table

Everyday cm values, converted

• 30 cm = 11.811 in — a school ruler.
• 100 cm = 39.3701 in — one metre.
• 180 cm = 70.8661 in — a frequently quoted adult height.

Where cm to in comes up

Length conversions come up in DIY and construction, screen and print sizing, running distances, and clothing or furniture measurements ordered from abroad. Mixed-unit plans are the usual reason a cut ends up wrong.

Doing cm to in in your head

Divide by 10 and multiply by 4, then shave a little off. 30 becomes 12, and the exact answer is 11.81.

Precision and rounding

One centimetre is exactly 0.393701 inches under the current definitions of both units, so the only judgement call is how many digits you keep. Two decimal places is already finer than most household scales and tape measures can read, while engineering and medical work usually keeps the full factor and rounds once at the end rather than at every step.