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 840 millimeters into decimeters we have to multiply 840 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

840 mm → L_(dm)

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

L_(dm) = 840 mm × 0.01 dm

L_(dm) = 8.4 dm

The final result is:

840 mm → 8.4 dm

We conclude that 840 millimeters is equivalent to 8.4 decimeters:

840 millimeters = 8.4 decimeters

Alternative conversion

We can also convert by utilizing the inverse value of the conversion factor. In this case 1 decimeter is equal to 0.11904761904762 × 840 millimeters.

Another way is saying that 840 millimeters is equal to 1 ÷ 0.11904761904762 decimeters.

Approximate result

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

840 mm ≅ 8.4 dm

An alternative is also that one decimeter is approximately zero point one one nine times eight hundred forty 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