About Mm to Cm Conversion

Converting millimeters to centimeters is common in printing, crafts, and design work. Paper sizes are typically specified in mm, while everyday measurements often use cm for convenience.

Where You'll Use This

Paper sizes — A4 paper is 210 mm × 297 mm (21 cm × 29.7 cm)
Printing — Understanding margins, bleed areas, and trim sizes
Crafts — Cutting precise pieces from specifications given in mm
Jewelry — Ring sizes and gem dimensions often use mm

The Simple Conversion

One centimeter equals 10 millimeters. To convert, divide mm by 10: 50 mm = 5 cm.

Paper Size Standards

The A-series paper sizes (A0 to A10) are defined in mm. A4, the most common, is 210 × 297 mm. Each size is exactly half the previous one when folded.

How to Convert Mm to Cm

Using This Tool

Enter millimeters in the top field
Read centimeters appearing below
Copy the result for your project

Paper Sizes Reference

Common paper sizes in both units:

A4 (210 mm × 297 mm) = 21 cm × 29.7 cm
A3 (297 mm × 420 mm) = 29.7 cm × 42 cm
A5 (148 mm × 210 mm) = 14.8 cm × 21 cm
Letter (216 mm × 279 mm) = 21.6 cm × 27.9 cm

Printing Measurements

Common print specifications:

3 mm bleed = 0.3 cm on each side
5 mm margin = 0.5 cm safety zone
Standard photo 4×6 = 102 mm × 152 mm = 10.2 cm × 15.2 cm

Quick Math

Move the decimal point one place left: 210 mm → 21.0 cm, 5 mm → 0.5 cm.

Features

Print-Focused Reference

The quick reference table shows standard paper sizes in both units. No need to look up A4 dimensions again.

Precise Results

Full decimal precision for design work where 0.5 mm matters.

Bidirectional

Convert cm to mm by entering in the bottom field. Useful when design software uses cm but print specs are in mm.

Copy for Design Tools

Copy the number for pasting into Photoshop, Illustrator, or any design software.

Always Accessible

Works anywhere — Use at the print shop or craft table
No account needed — Instant access
Private — Your project measurements aren't stored

Frequently Asked Questions

How many mm in 1 cm?

Exactly 10 millimeters. The prefix "milli" means one-thousandth (of a meter), while "centi" means one-hundredth.

What size is A4 paper in cm?

A4 is 21 cm × 29.7 cm (210 mm × 297 mm). It's the standard office paper size in most countries outside North America.

How do I convert mm to cm for printing?

Divide by 10. A 3 mm bleed becomes 0.3 cm. Most design software accepts either unit; check your preferences panel.

Why are paper sizes in mm?

The ISO 216 paper standard uses mm for precision. Paper manufacturing requires exact dimensions to ensure sheets fold and fit properly.

What's the difference between A4 and Letter?

A4 (210 × 297 mm) is slightly narrower and taller than US Letter (216 × 279 mm). This difference can cause formatting issues when printing international documents.

Millimeters to Centimeters