Length converter
Centimeters to millimeters.
Move between centimeter readings and millimeter dimensions without losing the decimal part.
The marker shows the fractional part of one inch. This diagram illustrates tick positions; it is not a physical-size ruler.
Conversion formula
millimeters = centimeters × 10
Enter the source length above. The result updates immediately. These calculations use exact length definitions: 1 m = 100 cm = 1000 mm, 1 in = 25.4 mm, and 1 ft = 12 in. Only the displayed answer and fractional ruler mark are rounded. The feet-and-inches output splits a length into whole feet and remaining inches; decimal feet do not encode an inch count.
Worked example
7.3 cm is 73 mm: seven whole centimeters contribute 70 mm, and the remaining 0.3 cm contributes 3 mm. On the ruler, this is the third small tick after the number 7.
Conversion table: cm → mm
Select a source value to load it into the calculator. Decimal results are displayed to at most six places; inch fractions in this table are rounded to 1/16 inch.
| Centimeters (cm) | Millimeters (mm) | Nearest inch fraction |
|---|---|---|
| 1 | ≈ 1/16 in | |
| 5 | ≈ 3/16 in | |
| 10 | ≈ 3/8 in | |
| 15 | ≈ 9/16 in | |
| 20 | ≈ 13/16 in | |
| 25 | ≈ 1 in | |
| 50 | ≈ 1 15/16 in | |
| 70 | ≈ 2 3/4 in | |
| 73 | ≈ 2 7/8 in | |
| 100 | ≈ 3 15/16 in | |
| 200 | ≈ 7 7/8 in | |
| 300 | ≈ 11 13/16 in |
When to use this conversion
Use this for school measurement exercises, small parts, labels, and specifications that ask for millimeters even though your first reading was in centimeters. Both units describe the same length on the same metric scale.
Count the spaces between marks. The mark at the starting edge is the origin, so it is not counted as the first millimeter.
Exact conversion versus a ruler reading
The unit relationship is exact, but a measured object may have uncertainty. At 1/16 inch, the maximum rounding difference is half a tick: 1/32 inch, or 0.79375 mm. The calculator shows the actual rounding difference for your value. Use a finer division only if the source measurement and physical instrument support that precision.
Next steps
Numerical conversion needs no display calibration. Comparing a physical object against your screen does. Use the ruler for small objects, a verified paper ruler away from your display, or an appropriate calibrated instrument for safety-critical measurements.
Related converters
Reference: NIST unit conversion factors. Calculations use the international foot, not historical survey-foot units. Fractions are explicitly approximate. NIST ↗