Convert Decimetre to Millimetre
Turn Decimetres into Millimetres in an instant. Type a value below to get an accurate dm → mm result, with the formula and a quick-reference table.
1 dm = 100 mm
Quick answer: 1 Decimetre = 100 Millimetre
Decimetre to Millimetre conversion table
| Decimetre (dm) | Millimetre (mm) |
|---|---|
| 1 dm | 100 mm |
| 2 dm | 200 mm |
| 5 dm | 500 mm |
| 10 dm | 1,000 mm |
| 20 dm | 2,000 mm |
| 50 dm | 5,000 mm |
| 100 dm | 10,000 mm |
| 500 dm | 50,000 mm |
| 1,000 dm | 100,000 mm |
How to convert Decimetre to Millimetre
To convert Decimetres to Millimetres, multiply the value by 100.
- Take your measurement in Decimetres.
- Multiply it by 100 — the number of Millimetres in one Decimetre.
- The result is the same amount, expressed in Millimetres.
To go the other way, multiply Millimetres by 0.01 — or simply divide by 100.
For example, a full metre (ten decimetres) is about 10 dm, which is 1,000 mm.
About Decimetre and Millimetre
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.
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.
Both the Decimetre and the Millimetre are metric units, so converting between them is just a change of scale: one Decimetre equals 100 Millimetres, and the Decimetre is the larger unit.
Other length conversions
Frequently asked questions
How many Millimetres are in a Decimetre?
1 Decimetre equals 100 Millimetre (dm → mm). To convert any amount, multiply the number of Decimetres by 100.
How do I convert Decimetre to Millimetre?
Enter the number of Decimetres in the converter above and read the result in Millimetres. It applies the exact dm → mm factor instantly, with full precision.
Is the Decimetre to Millimetre 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.