The decision when to use kilometers and when to use meters is sort of arbitrary. But usually you would use kilometers when you expect the distance to be close to a kilometer, or larger than a kilometer. For example, distances between towns or cities are often expressed in kilometers.
Use units of millimeters, meters, or kilometers.
you would use kilometers.
Americans use miles as the traditional measure of distance.
Kilometers are a unit of length, used to measure distance.
Miles or kilometers
Kilometers
You would use a length/distance unit, such as meters or kilometers.
kilometers
Kilometers
miles or kilometers
kilometers or miles
I would typically use kilometers to measure the distance between Delhi and Mumbai, as it is a commonly used unit of length for measuring geographic distances in India.