Conversion formula

The conversion factor from millimeters to decimeters is 0.01, which means that 1 millimeter is equal to 0.01 decimeters:

1 mm = 0.01 dm

To convert 400 millimeters into decimeters we have to multiply 400 by the conversion factor in order to get the length amount from millimeters to decimeters. We can also form a simple proportion to calculate the result:

1 mm → 0.01 dm

400 mm → L_(dm)

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

L_(dm) = 400 mm × 0.01 dm

L_(dm) = 4 dm

The final result is:

400 mm → 4 dm

We conclude that 400 millimeters is equivalent to 4 decimeters:

400 millimeters = 4 decimeters

Alternative conversion

We can also convert by utilizing the inverse value of the conversion factor. In this case 1 decimeter is equal to 0.25 × 400 millimeters.

Another way is saying that 400 millimeters is equal to 1 ÷ 0.25 decimeters.

Approximate result

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

400 mm ≅ 4 dm

An alternative is also that one decimeter is approximately zero point two five times four hundred millimeters.

Conversion table

millimeters to decimeters chart

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