Kilometres per hour

Kilometres per hour (American English: kilometers per hour) is a unit of both speed (scalar) and velocity (vector). The unit symbol is km/h or km·h⁻¹. The incorrect abbreviations "kph" and "kmph" are sometimes also seen in English-speaking countries, in analogy to mph. In North American slang and military usage, km/h (as well as km) is commonly pronounced, and sometimes even written, as klicks or kays (K's).

By definition, an object travelling at a speed of 1 km/h in a straight line for 1 hour moves 1 kilometre.

The km/h is the worldwide most commonly used speed unit on road signs and car speedometers. Therefore, it is far more common in everyday usage than the proper SI unit of speed, m/s. Along with the kWh, km/h is the most commonly used metric unit based on the hour, which is only a "non-SI unit accepted for use with the International System of Units" by the BIPM.^[1]

[edit] Conversions

• 3.6 km/h ≡ 1 m/s, the SI derived unit of speed, metre per second
• 1 km/h ≈ 0.277 78 m/s
• 1 km/h ≈ 0.621 37 mph ≈ 0.911 34 feet per second
• 1 knot ≡ 1.852 km/h (exactly)
• 1 mile = 1.609344 km (~1.61 km)^[2]
• km/h = ~1.61 * mph

[edit] See also

• Orders of magnitude (speed)

[edit] References

1. ^ BIPM brochure (SI reference)
2. ^ Converting a mile to kilometres: with 1 inch = 2.54 cm, centimeters per mile = 5280 ft * 12 inches/ft * 2.54 cm/inch = 160934.4 cm, then dividing by 100_000 cm in 1 km, 1 mile = 1.609344 km.

[edit] External links

• The converter Online conversions for speed units: km/h, mph, knots, etc.
• Conversion Calculator for Units of Speed

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