kilometre, km, K (kilometre), kilometres per hour, km²

Leave a space between kilometre (or its symbol km) and the number that immediately precedes it.

  • It is two kilometres from here to the lake.

SI usage, followed in scientific and technical writing, prescribes that both the number and the unit name be written in full (e.g. fifteen kilometres) or that the numeral be followed by the symbol (e.g. 15 km). However, general usage accepts numerals with spelled-out unit names (e.g. 15 kilometres), to improve comprehension.

  • Matthew received a ticket for driving 55 kilometres per hour in a school zone.

When no specific figure is stated, write kilometre in full.

  • The first bolts of lightning struck near the lake—just a kilometre away.

Symbol km

Because the metric (SI) system uses symbols, not abbreviations, the symbol km for kilometre does not contain periods, or an s in the plural form.

  • From Winnipeg, it is 2,306 km to Vancouver and 2,372 km to Montréal.

The symbol km is always in lower case, even when the rest of the text is in upper case, as in a newspaper headline.


Kilometres per hour is expressed as km/h (not kmh or kph).

  • A good cyclist can travel at 25 km/h for hours on end.

Area and volume in the metric system are expressed by means of superscript numerals: not square kilometres but km².

  • The area of the Lazy K Ranch was only 52 km².


For the sake of clarity, when kilometre is used as a modifier, a hyphen is inserted between the numeral and the unit name.

  • In this ten-kilometre race, participants may run, walk or bicycle.

However, if the symbol km is used, do not put a hyphen between the numeral and the symbol.

  • In this 10 km race, participants may run, walk or bicycle.

K is not an official symbol for kilometres, but races are often described by this letter. Do not leave a space or put a hyphen between the numeral and the symbol K.

  • Juanita ran a 10K (or a 10 km) race in her best time yet.

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