🚀 Speed Converter
mph, km/h, m/s, knots. Runs privately in your browser.
Distance over time, anchored to metres per second
Speed units are distance-per-time compounds, so each factor is defined per metre-per-second: 1 km/h = 1000/3600 m/s ≈ 0.27778, 1 mph = 0.44704 m/s exactly, 1 knot = 1852 m/h ≈ 0.514444 m/s. The converter reduces everything to m/s, then builds the target unit.
Knots deserve a note: a knot is one nautical mile per hour, where the nautical mile (1852 m) is defined as one minute of latitude — which is why aviation and marine charts still use it. mph-to-knots mixups in weather reporting are common because both appear in forecasts.Athletics and cycling add a fifth context: pace. Runners speak in minutes-per-kilometre or minutes-per-mile, which is the inverse of speed — a 5:00/km pace is 12 km/h. To convert pace to speed, divide 60 by the pace in minutes (60 ÷ 5 = 12 km/h); to get pace from speed, divide 60 by the speed. The converter handles the speed side; the pace arithmetic is one division away.
target = value × (factor_from ÷ factor_to) with m/s as base: kmh 0.277778, mph 0.44704, kn 0.514444.
Motorway traffic, cruising jets, sprinters
100 km/h: 27.78 m/s and 62.14 mph. A 747 cruising at 490 knots: 903.3 km/h ≈ 561 mph. A 10-second 100 m sprinter averages 10 m/s = 36 km/h. A 15-knot wind: 27.8 km/h.
Knots, mph and wind-speed confusion
- Confusing knots with mph in marine/aviation contexts — a 100-knot limit is 115 mph, not 100.
- Reading EU wind forecasts (km/h) against US ones (mph) without converting.
- Forgetting that m/s values look 'small' but are fast: 30 m/s is 108 km/h.
- Applying road-speed intuition to cycling speeds — 40 km/h on a bike is exceptional, in a car it's slow.Confusing average speed with average of speeds. A return trip at 60 km/h out and 30 km/h back averages 40 km/h (harmonic mean), not 45.
Speed questions
How fast is 100 km/h in mph?
62.14 mph. Enter 100 km/h to confirm — the 0.62137 factor is exact.
What is a knot?
One nautical mile (1852 m) per hour = 1.852 km/h = 1.15078 mph. Used in shipping and aviation.
Mach — is that included?
Not in this set; Mach varies with altitude and temperature, so it isn't a fixed factor.
Why is 1 mph exact but km/h not?
Because mph is defined from the inch (25.4 mm exact), while km/h divides an hour unevenly into seconds.
What speed is 30 m/s?
108 km/h ≈ 67.1 mph — highway speed.
How do I convert running pace to km/h?
Divide 60 by pace in minutes per km. 5:30/km → 60/5.5 ≈ 10.9 km/h.
What is 60 mph in km/h?
60 × 1.609344 = 96.56 km/h — the common '100 km/h ≈ 62 mph' pair inverted.
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Tip: double-check inputs before relying on results for important decisions.