Convert Millimetre to Decimetre
Turn Millimetres into Decimetres in an instant. Type a value below to get an accurate mm → dm result, with the formula and a quick-reference table.
1 mm = 0.01 dm
Quick answer: 1 Millimetre = 0.01 Decimetre
Millimetre to Decimetre conversion table
| Millimetre (mm) | Decimetre (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 |
| 50 mm | 0.5 dm |
| 100 mm | 1 dm |
| 500 mm | 5 dm |
| 1,000 mm | 10 dm |
How to convert Millimetre to Decimetre
To convert Millimetres to Decimetres, multiply the value by 0.01.
- Take your measurement in Millimetres.
- Multiply it by 0.01 — the number of Decimetres in one Millimetre.
- The result is the same amount, expressed in Decimetres.
To go the other way, multiply Decimetres by 100 — or simply divide by 0.01.
For example, a sharp pencil tip is about 0.5 mm, which is 0.005 dm.
About Millimetre and Decimetre
A millimetre is one-thousandth of a metre (1/1000 m) — the smallest line printed on a standard ruler. It is the everyday unit for fine measurements such as engineering tolerances, screw threads, paper thickness and rainfall.
A decimetre is one-tenth of a metre, or 10 centimetres. It is rarely used in daily life but appears in science — a cubic decimetre is exactly one litre.
Both the Millimetre and the Decimetre are metric units, so converting between them is just a change of scale: one Millimetre equals 0.01 Decimetres, and the Decimetre is the larger unit.
Other length conversions
Frequently asked questions
How many Decimetres are in a Millimetre?
1 Millimetre equals 0.01 Decimetre (mm → dm). To convert any amount, multiply the number of Millimetres by 0.01.
How do I convert Millimetre to Decimetre?
Enter the number of Millimetres in the converter above and read the result in Decimetres. It applies the exact mm → dm factor instantly, with full precision.
Is the Millimetre to Decimetre converter free?
Yes — it is completely free and unlimited, needs no sign-up, and runs right in your browser, so it is instant and private.
Is the conversion accurate?
Yes. It uses the internationally defined length factors and full floating-point precision, then rounds the display to a clean, readable number.