How this calculator works
The milli prefix means 10^-3 and kilo means 10^3. A millimetre is therefore one millionth of a kilometre. This large ratio is useful when a survey or CAD export stores a long route in millimetres but the report needs kilometres.
Formula
km = mm / 1000000; mm = km x 1000000.
Worked example
A 2500000 mm path is exactly 2.5 km. A 0.075 km cable is exactly 75000 mm.
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Frequently asked questions
Why divide by a million?
A kilometre has 1000 metres, and each metre has 1000 millimetres.
Does this apply to square millimetres?
No. For area the length factor must be squared.
Can it convert a drawing distance to ground distance?
Only after applying the drawing scale. This page converts the same physical length between units.