Millimeters to Centimeters (mm to cm) Converter

Millimeters to Centimeters

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

One centimetre equals 10 mm. To convert, divide millimetres by 10 (move the decimal one place left): 50 mm = 5 cm.

Where You'll Use This

Paper Sizes

A4 paper is 210 mm × 297 mm, which is 21 cm × 29.7 cm.

Printing

Understand margins, bleed areas, and trim sizes specified in mm.

Crafts & Jewellery

Cut precise pieces and read ring or gem dimensions given in mm.

How to Use This Converter

Enter millimetres

Type the mm value in the top field. Centimetres appear instantly below.

Read centimetres

The result updates live — full decimal precision for design work.

Copy or swap

Copy the number for design software, or swap to convert cm back to mm.

Conversion Formula

cm = mm ÷ 10 • Just move the decimal one place left. 210 mm → 21.0 cm; 5 mm → 0.5 cm.

Common Paper & Print Sizes

Size	Millimetres	Centimetres
A4	210 × 297 mm	21 × 29.7 cm
A3	297 × 420 mm	29.7 × 42 cm
A5	148 × 210 mm	14.8 × 21 cm
Letter	216 × 279 mm	21.6 × 27.9 cm

Features

Instant As-You-Type Results

The result updates the moment you enter a number — no button to press, no page reload.

One-Click Swap

The swap button between the two fields reverses the direction instantly, so you can convert back without retyping.

Copy Without the Unit

Each field has its own copy button that grabs only the number, ready to paste into forms, spreadsheets, or documents.

Searchable Unit Picker

Each dropdown has a search box — switch to any other length unit and use it as a general-purpose converter.

Print & Design Tips

Print Specifications

A 3 mm bleed is 0.3 cm on each side; a 5 mm margin is a 0.5 cm safety zone.

A-Series Logic

ISO 216 sizes are defined in mm. Each size is exactly half the previous one when folded.

Always accessible, fully private. Use it at the print shop or craft table — no account needed and your project measurements aren't stored.

Frequently Asked Questions

How many mm are in 1 cm?

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

What size is A4 paper in cm?

A4 is 21 cm × 29.7 cm (210 mm × 297 mm) — 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 the preferences panel.

Why are paper sizes given in mm?

The ISO 216 paper standard uses mm for precision. Paper manufacturing needs exact dimensions so 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). The difference can cause formatting issues when printing international documents.

Millimeters to Centimeters