Convert between m/s, km/h, mph, knots, ft/s, ft/min, cm/s, mm/s, Mach, km/s and mi/min with instant bidirectional output and click-to-copy values.
Formula & how it works
All inputs are first normalized to meters per second (the SI base), then each target unit is computed with its conversion factor. This avoids rounding chains when converting between arbitrary pairs.
Conversion table — common road speeds
| km/h | mph | m/s | ft/s | knots |
|---|
Frequently asked questions
How do I convert km/h to mph?
Multiply km/h by 0.621371. For a mental shortcut, multiply by 5 and divide by 8 — this gives a result within 0.4%. Example: 100 km/h × 0.621371 ≈ 62.14 mph.
How do I convert m/s to km/h?
Multiply m/s by 3.6. The factor comes from 3 600 seconds in an hour divided by 1 000 meters in a kilometer. Example: 10 m/s × 3.6 = 36 km/h.
What is a knot and why is it different?
One knot equals one nautical mile per hour, and a nautical mile is 1 852 meters (one minute of latitude along a meridian). So 1 knot = 1.852 km/h = 0.5144 m/s. Knots are standard in marine navigation and aviation.
What is Mach 1 exactly?
Mach is the ratio of an object's speed to the local speed of sound. At sea level in dry air at 15 °C, Mach 1 ≈ 340.29 m/s ≈ 1 225 km/h ≈ 761 mph. In colder air at altitude, the speed of sound drops, so the same Mach number corresponds to a lower true airspeed.
How accurate are these conversions?
All conversion factors use the internationally defined values: 1 mile = 1 609.344 m, 1 foot = 0.3048 m, 1 nautical mile = 1 852 m. Results are displayed with up to 6 significant digits — enough for engineering, navigation and everyday use.
Why convert everything through m/s?
m/s is the SI base unit for speed, so it acts as a neutral hub: value × factor(in) = m/s, then m/s × factor(out) = target. Chaining direct pair conversions (km/h→mph→ft/s…) would accumulate rounding errors.
Speed Converter handles eleven units in one place: meters per second, kilometers per hour, miles per hour, knots, feet per second, feet per minute, centimeters per second, millimeters per second, kilometers per second, miles per minute, and Mach. Enter a value, pick the source unit, and every other unit is computed instantly. All inputs are first normalized to m/s (the SI base unit) and then re-expressed, which avoids rounding chains when converting between arbitrary pairs. Quick presets cover walking (5 km/h), cycling (25 km/h), highway driving (120 km/h), jet cruise (800 km/h), the speed of sound (340 m/s) and the speed of light (299 792 km/s). Example: enter 100 km/h and the grid shows 62.14 mph, 27.78 m/s, 91.13 ft/s, 53.996 knots and Mach 0.0816. A conversion table lists typical road speeds side by side for quick reference.