Decimeters to Millimeters
Convert decimeters to millimeters instantly — one decimeter is 100 millimeters.
| Decimeters | Millimeters |
|---|---|
| 1 dm | 100 mm |
| 2 dm | 200 mm |
| 3 dm | 300 mm |
| 5 dm | 500 mm |
| 10 dm | 1000 mm |
| 25 dm | 2500 mm |
| 50 dm | 5000 mm |
| 100 dm | 10000 mm |
How to use
- Enter a value in the Decimeters field.
- The Millimeters figure appears immediately — no button to press.
- Typing in the Millimeters field converts back to Decimeters the same way.
- Use the reference table for the values that come up most often.
Decimeters to Millimeters formula
The factor from decimeters to millimeters is 100.
mm = dm × 100
Put another way, one decimeter is exactly 100 millimeters.
Why this factor: the decimeter and the millimeter are both defined against the meter, so dividing one definition by the other gives 100 directly. Both definitions are set out in full below.
To go the other way, divide by 100 — or use the Millimeters to Decimeters converter, which is the same calculation reversed.
Worked example
Given 100 dm, multiplying by 100 yields 10000 mm.
100 dm × 100 = 10000 mm
The converter above does this for any value you type, in either direction.
What is a decimeter?
A decimeter is one tenth of a meter — 10 centimeters.
Definition: Exactly 0.1 meter by SI prefix definition.
Where it is used: Rare in everyday speech, but it matters because a cubic decimeter is exactly one liter.
Worth knowing: The decimeter's real importance is volumetric: 1 dm³ = 1 L exactly, which is where the liter comes from.
What is a millimeter?
A millimeter is one thousandth of a meter — the working precision unit of manufacturing and construction.
Definition: Exactly 0.001 meter by SI prefix definition.
Where it is used: Engineering drawings, machining tolerances, timber and steel dimensions, rainfall totals.
Decimeters vs Millimeters
The decimeter and the millimeter belong to the same family of units, so converting between them is usually a matter of shifting a decimal point or applying a small whole-number factor.
Frequently asked questions
How many millimeters are in a decimeter?
One decimeter equals 100 millimeters.
What is the formula to convert decimeters to millimeters?
Multiply the number of decimeters by 100. To reverse it, divide by 100 instead.
How do I convert millimeters back to decimeters?
Divide by 100, which is the same as multiplying by 0.01.
How many millimeters are in 10 decimeters?
10 dm works out to 1000 mm.
Is there anything to watch out for with decimeters?
The decimeter's real importance is volumetric: 1 dm³ = 1 L exactly, which is where the liter comes from.
How is the decimeter defined?
Exactly 0.1 meter by SI prefix definition.