4 decimeters in millimeters

Conversion formula
How to convert 4 decimeters to millimeters?

We know (by definition) that: $1\mathrm{dm}=100\mathrm{mm}$

We can set up a proportion to solve for the number of millimeters.

Now, we cross multiply to solve for our unknown $x$:

Conclusion: 4 ⁢ dm = 400 ⁢ mm

Conversion in the opposite direction

The inverse of the conversion factor is that 1 millimeter is equal to 0.0025 times 4 decimeters.

It can also be expressed as: 4 decimeters is equal to $\frac{1}{\mathrm{0.0025}}$ millimeters.

Approximation

An approximate numerical result would be: four decimeters is about four hundred millimeters, or alternatively, a millimeter is about zero times four decimeters.