Kilometers to Millimeters Converter

Enter the length in kilometers below to get the value converted to millimeters.

Results in Millimeters:
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1 km = 1,000,000 mm
1 km = 100,000 cm
1 km = 1,000 m

Do you want to convert millimeters to kilometers?

How to Convert Kilometers to Millimeters

To convert a measurement in kilometers to a measurement in millimeters, multiply the length by the following conversion ratio: 1,000,000 millimeters/kilometer.

Since one kilometer is equal to 1,000,000 millimeters, you can use this simple formula to convert:

millimeters = kilometers × 1,000,000

The length in millimeters is equal to the length in kilometers multiplied by 1,000,000.

For example, here's how to convert 5 kilometers to millimeters using the formula above.
millimeters = (5 km × 1,000,000) = 5,000,000 mm

How Many Millimeters Are in a Kilometer?

There are 1,000,000 millimeters in a kilometer, which is why we use this value in the formula above.

1 km = 1,000,000 mm

Our inch fraction calculator can add kilometers and millimeters together, and it also automatically converts the results to US customary, imperial, and SI metric values.

Kilometers and millimeters are both units used to measure length. Keep reading to learn more about each unit of measure.

What is a Kilometer?

One kilometer is equal to 1,000 meters, which are defined as the distance light travels in a vacuum in a 1/299,792,458 second time interval.[1] One kilometer is equal to 0.621371 miles.

The kilometer, or kilometre, is a multiple of the meter, which is the SI base unit for length. In the metric system, "kilo" is the prefix for thousands, or 103. Kilometers can be abbreviated as km; for example, 1 kilometer can be written as 1 km.

Learn more about kilometers.

What is a Millimeter?

One millimeter is equal to one-thousandth (1/1,000) of a meter, which is defined as the distance light travels in a vacuum in 1/299,792,458 of a second. One millimeter is equal to 0.0393701 inches.

The millimeter, or millimetre, is a multiple of the meter, which is the SI base unit for length. In the metric system, "milli" is the prefix for thousandths, or 10-3. Millimeters can be abbreviated as mm; for example, 1 millimeter can be written as 1 mm.

Millimeters are often represented by the smallest ticks on most metric rulers. To get a reference point of the size, the thickness of a US dime is 1.35mm.[2]

Learn more about millimeters.

We recommend using a ruler or tape measure for measuring length, which can be found at a local retailer or home center. Rulers are available in imperial, metric, or a combination of both values, so make sure you get the correct type for your needs.

Need a ruler? Try our free downloadable and printable rulers, which include both imperial and metric measurements.

Kilometer to Millimeter Conversion Table

Table showing various kilometer measurements converted to millimeters.
Kilometers Millimeters
0.000001 km 1 mm
0.000002 km 2 mm
0.000003 km 3 mm
0.000004 km 4 mm
0.000005 km 5 mm
0.000006 km 6 mm
0.000007 km 7 mm
0.000008 km 8 mm
0.000009 km 9 mm
0.0000001 km 0.1 mm
0.000001 km 1 mm
0.00001 km 10 mm
0.0001 km 100 mm
0.001 km 1,000 mm
0.01 km 10,000 mm
0.1 km 100,000 mm
1 km 1,000,000 mm


  1. Ambler Thompson and Barry N. Taylor, Guide for the Use of the International System of Units (SI), National Institute of Standards and Technology,
  2. United States Mint, Coin Specifications,

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