## Conversion formula

The conversion factor from decimeters to millimeters is 100, which means that 1 decimeter is equal to 100 millimeters:

1 dm = 100 mm

To convert 21 decimeters into millimeters we have to multiply 21 by the conversion factor in order to get the length amount from decimeters to millimeters. We can also form a simple proportion to calculate the result:

1 dm → 100 mm

21 dm → L(mm)

Solve the above proportion to obtain the length L in millimeters:

L(mm) = 21 dm × 100 mm

L(mm) = 2100 mm

The final result is:

21 dm → 2100 mm

We conclude that 21 decimeters is equivalent to 2100 millimeters:

21 decimeters = 2100 millimeters

## Alternative conversion

We can also convert by utilizing the inverse value of the conversion factor. In this case 1 millimeter is equal to 0.00047619047619048 × 21 decimeters.

Another way is saying that 21 decimeters is equal to 1 ÷ 0.00047619047619048 millimeters.

## Approximate result

For practical purposes we can round our final result to an approximate numerical value. We can say that twenty-one decimeters is approximately two thousand one hundred millimeters:

21 dm ≅ 2100 mm

An alternative is also that one millimeter is approximately zero times twenty-one decimeters.

## Conversion table

### decimeters to millimeters chart

For quick reference purposes, below is the conversion table you can use to convert from decimeters to millimeters

decimeters (dm) millimeters (mm)
22 decimeters 2200 millimeters
23 decimeters 2300 millimeters
24 decimeters 2400 millimeters
25 decimeters 2500 millimeters
26 decimeters 2600 millimeters
27 decimeters 2700 millimeters
28 decimeters 2800 millimeters
29 decimeters 2900 millimeters
30 decimeters 3000 millimeters
31 decimeters 3100 millimeters