To convert millimeters to centimeters, divide by 10. So 10 mm = 1 cm, 25 mm = 2.5 cm, and 100 mm = 10 cm. The factor is exact - 1 cm = 10 mm by the SI metric prefix system.
- Exact factor: 1 cm = 10 mm (SI prefix definition, no approximation).
- 10 mm = 1 cm. 25 mm = 2.5 cm. 100 mm = 10 cm = 1 dm.
- The conversion is a simple decimal shift - just move the decimal point one place left.
- Common use cases: sewing patterns, woodworking, medical measurements.
How to Use This Converter
Type any millimeter value in the mm field and the centimeters result appears instantly. You can also type in the cm field to convert back to millimeters - it works in both directions without pressing a button.
How Do You Convert Millimeters to Centimeters?
Divide millimeters by 10. The relationship is exact: the SI prefix "centi-" means 1/100 and "milli-" means 1/1000, so there are exactly 10 mm in every centimeter. No rounding is ever needed.
$$\text{cm} = \text{mm} \div 10$$
Worked examples: 5 mm = 0.5 cm. 10 mm = 1 cm. 50 mm = 5 cm. 100 mm = 10 cm. 210 mm = 21 cm (A4 paper width).
Mental shortcut: simply move the decimal point one place to the left. 125 mm → 12.5 cm. This is the simplest conversion in the metric system.
How Do You Convert Centimeters to Millimeters?
Multiply centimeters by 10. For a dedicated reverse converter, see the centimeters to millimeters converter.
$$\text{mm} = \text{cm} \times 10$$
Worked examples: 1 cm = 10 mm. 2.5 cm = 25 mm. 30 cm = 300 mm (standard ruler length).
Millimeters to Centimeters Reference Table
Common values converted at the exact factor of 0.1:
| Millimeters | Centimeters | Common context |
|---|---|---|
| 1 mm | 0.1 cm | Fine line on a ruler |
| 5 mm | 0.5 cm | Standard pencil diameter |
| 10 mm | 1 cm | Small button diameter |
| 25 mm | 2.5 cm | Approx. 1 inch (25.4 mm exactly) |
| 50 mm | 5 cm | Standard camera filter rim |
| 100 mm | 10 cm | Smartphone width (approx.) |
| 150 mm | 15 cm | 6-inch ruler |
| 210 mm | 21 cm | A4 paper width |
| 297 mm | 29.7 cm | A4 paper height |
| 300 mm | 30 cm | Standard 30 cm ruler |
| 500 mm | 50 cm | Half a meter |
| 1000 mm | 100 cm | 1 meter exactly |
When Do You Need to Convert Millimeters to Centimeters?
Within the metric system, mm and cm are the two most common small-length units. The conversion is needed when measurements come from different sources or instruments:
- Sewing and crafts - patterns often mix mm and cm; seam allowances in mm, fabric widths in cm.
- Woodworking - European rulers show both; joinery and inlay work is often specified in mm, room dimensions in cm.
- Medical - tumour sizes and wound measurements are recorded in mm; height and anatomy in cm.
- Photography - focal lengths and sensor dimensions are in mm; print sizes are in cm.
- Engineering drawings - tolerances in mm, overall part dimensions often in cm for readability.
Frequently Asked Questions
How many cm is 1 mm?
1 mm equals 0.1 cm. There are 10 millimeters in one centimeter, so 1 mm is one-tenth of a centimeter. In decimal notation: 1 mm = 0.1 cm = 0.001 m.
How do you convert mm to cm?
Divide by 10, or equivalently move the decimal point one place to the left. This is the simplest conversion in the SI system. 125 mm → 12.5 cm. 7 mm → 0.7 cm.
How many mm is 1 cm?
Exactly 10 mm. Use the centimeters to millimeters converter to check any cm value. For converting further to inches, see the mm to inches converter.
What is 25 mm in cm?
25 mm equals 2.5 cm. This is close to 1 inch (which is exactly 25.4 mm = 2.54 cm). For mm to inches, use the millimeters to inches converter.