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15 things in the Megametre group
1 megametre =
SI units
1,000.00 km 1.000×10^6 m
Astronomical units
6.685×10^−6 AU 105.70000181838×10^−12 ly
US customary / Imperial units
621.37 mi 3.281×10^6 ft

The megametre (International spelling as used by the International Bureau of Weights and Measures; SI symbol: Mm) or megameter (American spelling) is a unit of length in the metric system, equal to one million metres, the SI base unit of length, hence to 1,000 km or approximately 621.37 miles.

Megametres (from the Greek words megas = big and metro = count/measure) are rarely seen in practical use, e.g. "5000 km" is much more common than "5 Mm". Unless dealing with astronomy, distances on Earth can't be more than 40,075 km (Equator length). The symbol (Mm) can also be confused with millimetres (mm) and care should be taken to use the correct capitalisation when using such symbols. Megametres are also occasionally found in science fiction.[citation needed]

See also[edit]