🦉 UnitOwl

Centimeters to Millimeters

1 Centimeter (cm) = 10 Millimeter (mm)

Result
10 mm
1 cm = 10 mm

How Many Millimeters in a Centimeter?

One centimeter equals exactly 10 millimeters. To convert centimeters to millimeters, multiply by 10 (or move the decimal point one place to the right). This is the simplest metric conversion — a clean factor of 10 with no decimals or approximation. Despite its simplicity, this conversion is used constantly in engineering, manufacturing, medicine, and crafts. Technical drawings and engineering specs almost always use millimeters, while rulers and tape measures may show centimeters. A surgeon measuring a wound at 2.3 cm records it as 23 mm. A 3D printer with 0.1 mm precision needs dimensions in millimeters, not centimeters.

How to Convert Centimeter to Millimeter

  1. Start with your measurement in centimeters (cm).
  2. Multiply by 10 to get millimeters (mm).
  3. Equivalently, move the decimal point one place to the right.
  4. Example: 5.7 cm × 10 = 57 mm.
  5. For fractions: 0.1 cm = 1 mm, 0.5 cm = 5 mm, 0.01 cm = 0.1 mm.

Real-World Examples

Engineering drawing: A part dimension is listed as 4.5 cm on a sketch
4.5 × 10 = 45 mm. The engineer would label the technical drawing as 45 mm per ISO standards.
Medical: A skin lesion measures 1.2 cm
1.2 × 10 = 12 mm. Medical records often switch between cm and mm depending on the size of the measurement.
Jewelry: A ring band is 0.6 cm wide
0.6 × 10 = 6 mm. Ring bands are typically described in millimeters, with 6 mm being a common width for men's wedding bands.
Photography: A lens filter is 7.7 cm in diameter
7.7 × 10 = 77 mm. Camera lens filters are sold by their diameter in millimeters — this is a 77 mm filter.
3D printing: A model needs walls that are 0.15 cm thick
0.15 × 10 = 1.5 mm. The slicer software expects dimensions in mm, so you would enter 1.5.

Quick Reference

Centimeter (cm) Millimeter (mm)
1 10
2 20
5 50
10 100
25 250
50 500
100 1,000
500 5,000
1,000 10,000

History of Centimeter and Millimeter

Both the centimeter and the millimeter are children of the meter, which was created during the French Revolution in the 1790s. The prefix "centi-" means one hundredth (1 cm = 1/100 meter), while "milli-" means one thousandth (1 mm = 1/1000 meter). This gives the clean 1:10 relationship between them. In practice, different fields adopted different preferences: French and German engineering traditions favored millimeters for technical drawings, while everyday measurements in many countries used centimeters. The ISO (International Organization for Standardization) eventually standardized on millimeters for technical drawings, which is why engineering and manufacturing worldwide use mm as their default unit.

Common Mistakes to Avoid

  • Dividing by 10 instead of multiplying. To go from cm to mm, the number should get larger (10 times larger). If your mm result is smaller than the cm value, you went the wrong direction.
  • Confusing cm with mm on a ruler. On a metric ruler, the longer lines are centimeters and the shorter lines between them are millimeters. There are exactly 10 mm divisions between each cm mark.
  • Mixing up cm and mm in technical contexts. An error of 1 cm vs 1 mm is a factor of 10 — a 50 mm part is very different from a 50 cm part. Always double-check your units.

Frequently Asked Questions

When should I use millimeters vs centimeters?
Use millimeters for engineering, manufacturing, medical measurements, and any precision work where avoiding decimals improves clarity. Use centimeters for everyday measurements like body height, clothing sizes, and general descriptions. The rule of thumb: if accuracy matters, use mm.
How many millimeters are in 1 meter?
Exactly 1,000 mm. Since 1 m = 100 cm and 1 cm = 10 mm, the total is 100 × 10 = 1,000 mm.
Is the cm-to-mm conversion always exact?
Yes, always. The relationship 1 cm = 10 mm is exact by definition. The metric system was designed specifically to have clean, exact decimal relationships between all its units.
Quick Tip

When reading a metric ruler, the numbered marks are centimeters and the smallest tick marks are millimeters. Counting from the 3 cm mark to the 4 cm mark, you will pass through 31, 32, 33... 39 mm. This makes metric rulers naturally bilingual in cm and mm without needing any conversion — just count the small ticks.