How many decimeters is 1 millimeter?

One millimeter equals exactly 0.01 dm (1/100 of a decimeter).

How many millimeters are in 1 decimeter?

One decimeter contains exactly 100 millimeters.

When would I convert mm to dm?

Rarely. The decimeter is mainly used for volume (1 dm3 = 1 L). For linear measurement, converting mm to cm or m is more common.

Millimeters to Decimeters (mm to dm) Converter

1 mm = 0.01 dm

1 Millimeter equals 0.01 Decimeters (1 mm = 0.01 dm). Convert Millimeters to Decimeters with formula, table, and examples.

One millimeter equals exactly 0.01 decimeters (10^-2 dm). A decimeter (100 mm) is about the width of a liter bottle. The millimeter measures engineering details; the decimeter defines the liter. Both are metric but serve different scales.

How to Convert Millimeters to Decimeters

dm = mm ÷ 100

Divide the value in Millimeters by 100

Take your value in Millimeters
Divide by 100
Read the result in Decimeters

Common Millimeters to Decimeters Conversions

Millimeters (mm)	Decimeters (dm)	Status
0.5 mm	0.005 dm
1 mm	0.01 dm
2 mm	0.02 dm
5 mm	0.05 dm
10 mm	0.1 dm
20 mm	0.2 dm
25 mm	0.25 dm
50 mm	0.5 dm
100 mm	1 dm
200 mm	2 dm
500 mm	5 dm
1,000 mm	10 dm
5,000 mm	50 dm

Good to Know About Millimeters to Decimeters Conversion

The millimeter and decimeter are like siblings who never talk. The mm dominates engineering drawings. The dm dominates through its cube (the liter). They share the same metric family but serve different professions. The mm builds things; the dm measures liquids.

Millimeters to Decimeters: What You Need to Know

100 mm = 1 dm. A 50 mm lens is 0.5 dm. An A4 sheet at 297 mm long is 2.97 dm. The decimeter's main significance is volumetric: 1 dm³ = 1 liter. But in linear measurement, the millimeter dominates engineering.

What is a Millimeter? mm

A metric unit of length equal to one thousandth of a meter. Used in engineering, manufacturing, and precise measurements.

Metric engineering manufacturing rainfall

Learn more about Millimeter →

What is a Decimeter? dm

One tenth of a meter, or 10 centimeters. Used in some European countries for everyday measurements and in education.

Metric European education everyday measurement

Learn more about Decimeter →

Going the other way? Use our Decimeters to Millimeters converter.

Millimeters to Decimeters FAQ

One millimeter equals exactly 0.01 dm (1/100 of a decimeter).
One decimeter contains exactly 100 millimeters.
Rarely. The decimeter is mainly used for volume (1 dm³ = 1 L). For linear measurement, converting mm to cm or m is more common.

Non-Frequently Asked Questions About Millimeters to Decimeters

Questions nobody should ask - but someone did.

An M&M is about 13 mm in diameter. 1 dm (100 mm) fits about 7.7 M&Ms. So about 8 M&Ms make a decimeter. This is the most delicious way to teach the metric system.
Roughly. A standard 1-liter water bottle is about 80-90 mm (0.8-0.9 dm) in diameter. The theoretical cube of 1 dm x 1 dm x 1 dm holds exactly 1 liter. Real bottles are taller and narrower to be grippable. The liter is a perfect cube; the bottle is a practical compromise.
A nano-SIM is 12.3 mm long. 1 dm (100 mm) fits about 8.1 SIM cards. Your entire mobile identity fits 8 times across a decimeter. Technology keeps shrinking; the decimeter stays the same size.