How many mm are in 1 cm?

There are exactly 10 millimetres in 1 centimetre. This is a straightforward metric conversion since "milli" means one-thousandth and "centi" means one-hundredth, so 1 cm = 10 mm. To convert mm to cm, simply divide by 10.

When should I use mm instead of cm?

Millimetres are preferred for precision work such as engineering drawings, woodworking tolerances, medical measurements (like tumour sizes), and rainfall amounts. Centimetres are more common for everyday measurements like clothing sizes, furniture dimensions, and body measurements.

How do I convert mm to inches?

Divide the millimetre value by 25.4 to get inches. For example, 100 mm = 100 / 25.4 = 3.937 inches. This converter shows the inch equivalent automatically alongside the centimetre result.

Millimetres to Centimetres Converter

Convert millimetres to centimetres and centimetres to millimetres

Published by UltraCalculatorsLast reviewed: 1 Apr 2026v1.0Report an issue

Millimetres and centimetres are both metric units of length, but they serve different purposes in everyday life. Millimetres offer the precision needed for engineering specifications, medical imaging, and fine woodworking, while centimetres are the go-to unit for clothing sizes, furniture dimensions, and general household measurements. The conversion between the two is straightforward: there are exactly 10 millimetres in every centimetre. Despite this simplicity, having a quick converter is useful when dealing with large numbers or when you also need the value in metres or inches. This is especially true in the UK, where metric and imperial measurements coexist and you might need to translate a measurement given in millimetres into something more intuitive. This tool converts in both directions and also displays the equivalent in metres and inches, giving you a complete picture of any measurement at a glance.

How to Use This Calculator

To use the millimetres to centimetres converter: 1. Select the conversion direction. Choose "Millimetres to Centimetres" if you have a measurement in mm. Choose "Centimetres to Millimetres" if you need to go the other way. 2. For mm to cm: Enter the number of millimetres. The converter divides by 10 and shows the result in centimetres, along with the equivalent in metres and inches. 3. For cm to mm: Enter the number of centimetres. The converter multiplies by 10 and shows the result in millimetres, with metres and inches alongside. 4. Results update instantly, making it easy to check multiple measurements in quick succession.

How It Works

The conversion is based on the metric system definition: 1 centimetre = 10 millimetres. Millimetres to Centimetres: cm = mm / 10 Metres = mm / 1,000 Inches = mm / 25.4 Example: 350 mm = 350 / 10 = 35 cm = 0.35 m = 13.78 inches Centimetres to Millimetres: mm = cm x 10 Metres = cm / 100 Inches = (cm x 10) / 25.4 Example: 7.5 cm = 7.5 x 10 = 75 mm = 0.075 m = 2.953 inches

Worked Examples

Example 1: Checking a drill bit size against a spec sheet

Inputs: Millimetres: 6.5. Direction: mm to cm.

Centimetres = 6.5 / 10 = 0.65 cm.
Metres = 6.5 / 1,000 = 0.0065 m.
Inches = 6.5 / 25.4 = 0.2559 inches (just over a quarter inch).

Result: 6.5 mm equals 0.65 cm or approximately a quarter of an inch.

Example 2: Converting rainfall measurement for a garden log

Inputs: Millimetres: 23. Direction: mm to cm.

Centimetres = 23 / 10 = 2.3 cm.
Metres = 23 / 1,000 = 0.023 m.
Inches = 23 / 25.4 = 0.9055 inches.

Result: 23 mm of rainfall equals 2.3 cm or just under 1 inch.

Example 3: Converting a phone screen size from cm to mm

Inputs: Centimetres: 16.95. Direction: cm to mm.

Millimetres = 16.95 x 10 = 169.5 mm.
Metres = 16.95 / 100 = 0.1695 m.
Inches = 169.5 / 25.4 = 6.673 inches.

Result: A 16.95 cm screen diagonal is 169.5 mm or about 6.67 inches.

Quick reference: 1 mm = 0.1 cm, 5 mm = 0.5 cm, 10 mm = 1 cm, 100 mm = 10 cm, 1,000 mm = 100 cm = 1 m. In the UK, rainfall is typically reported in millimetres (the annual average for London is about 600 mm or 60 cm). Medical scans often describe findings in millimetres for precision. For DIY projects, timber dimensions in the UK are usually given in millimetres (e.g., 50 x 100 mm rather than 5 x 10 cm).