CM to MM Converter

How to convert centimeters to millimeters

1 centimeter = 10 millimeters. To convert centimeters to millimeters, multiply by 10. A centimeter is one hundredth of a meter. A millimeter is one thousandth of a meter.

Worked examples

• 0.5 centimeters = 5 mm (0.5 × 10)
• 2.5 centimeters = 25 mm (2.5 × 10)
• 30 centimeters = 300 mm (30 × 10)

Where this conversion comes up

Centimeters are used for body height, clothing and furniture sizes; millimeters for screw and drill sizes, rainfall, paper and phone dimensions. Both are metric, so it is just a decimal shift: 1 cm is 10 mm. Rulers show it directly; the ten small ticks between centimeter marks are millimeters.

Quick estimate

Move the decimal point one place right: 2.5 cm = 25 mm.

Common mistakes

• Dividing instead of multiplying. A millimeter is smaller than a centimeter, so the number of millimeters must come out larger: 0.5 centimeters = 5 mm.
• Rounding too early. Keep the full factor until the last step; rounding 10 to 10 first puts large values noticeably off.

Related length converters: mm to inches, inches to mm, inches to feet, feet to inches, meters to feet, feet to meters.