Speed Converter
Kilometres per hour, miles per hour, metres per second, knots and more — and the same speed written as a running pace. Nothing is uploaded.
| Unit | Speed |
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How to use it
- Type the speed and pick the unit it is already in.
- Every other unit fills in at once — nothing to convert twice.
- The pace tiles read the same speed the way a runner does, in minutes and seconds per kilometre and per mile.
The conversions worth knowing by heart
km/h to mph: multiply by 5 and divide by 8. The real factor is 0.6214 and this shortcut gives 0.625, which is close enough to read a road sign. It is also why 80 km/h and 50 mph are treated as the same limit: 80 times five eighths is exactly 50.
m/s to km/h: multiply by 3.6, because an hour is 3600 seconds and a kilometre is 1000 metres. Physics gives answers in m/s and everyday life wants km/h, so this is the one that comes up most in homework.
knots to km/h: multiply by 1.852, exactly. A nautical mile was defined as 1852 metres, so the conversion is a definition rather than a measurement.
Speed and pace are the same thing upside down
A speed says how far you go in a fixed time. A pace says how long you take over a fixed distance. Runners think in pace because a race is a known distance, so one divided by the other gets you between them.
The consequence catches people out: a faster runner has a smaller pace. Going from 5:00 per kilometre to 4:30 is an improvement, and the number went down. It also means pace cannot be averaged the way speeds can — two kilometres at 4:00 and 6:00 do not average to a 5:00 pace over the pair.
At zero there is no pace at all. Standing still does not take a very long time to cover a kilometre; it never covers one. The tiles say so rather than printing an enormous number.
A note on Mach
Mach 1 is the speed of sound, and the speed of sound is not a fixed number. It depends almost entirely on air temperature, falling as the air gets colder. This page uses 340.29 m/s, the standard figure for dry air at sea level and 15 °C.
High up where airliners fly it is nearer 295 m/s, so the same Mach number is a slower true speed. Treat the Mach line here as a sea-level reference, not as a reading for an aircraft at altitude.
Frequently asked questions
How do I convert km/h to mph in my head?
Multiply by 5 and divide by 8. That gives 0.625 where the true figure is 0.6214, so 80 km/h comes out as 50 mph against a real 49.7. It is close enough for a speed limit sign and it is the reason 80 km/h and 50 mph are treated as the same limit in practice.
Why are boats and planes measured in knots?
A knot is one nautical mile an hour, and a nautical mile is one minute of latitude — one sixtieth of a degree. That makes navigation arithmetic simple on a chart: sixty nautical miles north is exactly one degree of latitude. The name comes from counting knots in a rope paid out behind a ship over a timed interval.
What pace is a five minute kilometre in minutes per mile?
About 8 minutes 3 seconds per mile, which is 12 km/h or 7.46 mph. A mile is 1.609 kilometres, so a per-mile pace is always the per-kilometre pace multiplied by roughly 1.61. Five minute kilometres for the full distance is a 3 hour 31 minute marathon.
Is anything I type sent anywhere?
No. The arithmetic happens in JavaScript inside your own browser. Nothing is uploaded and nothing is saved - close the tab and it is gone.