meters
Metres (in a built-up area), kilometres if across open spaces.
I would use a yardstick, a foot ruler, a tape measure, a meter stick, or a laser rangefinder to make the measurement. After I knew the distance, I could convert it into any convenient unit in order to describe it or report it to others. The most convenient metric units would be either meters or centimeters.
Kilometre.
You would use kilometers.
Meters
distance
A global positioning system (GPS)
A metric ruler.
You would typically use the metric unit "kilometers" to measure the distance from home to school.
Kilometers
kilometers
meters
You would use the unit "meter" in the metric system to measure the distance from point A to point B.
Metres (in a built-up area), kilometres if across open spaces.
Miles is best.
A calculator would be between 100 and 150 millimetres.