There are 1,000,000 (one million) millimeters in a kilometer.
The prefix “kilo-” in the metric system denotes a factor of 1,000. So, when you have 1 kilometer (1 km), you can convert it to millimeters by multiplying by 1,000:
1 kilometer = 1,000 meters 1 meter = 1,000 millimeters
Therefore:
1 kilometer = 1,000 meters x 1,000 millimeters/meter = 1,000,000 millimeters
So, there are 1,000,000 millimeters in 1 kilometer.
Also Read: How do you convert mm to km