Metric speed units
Meters per second (m/s) is the SI unit. Kilometers per hour (km/h) is the everyday driving unit in most of the world. 1 m/s equals exactly 3.6 km/h.
Speed conversion
Convert any speed,
instantly.
From a stroll in cm/s to the speed of light — every common scale, side by side.
km/h
0.62137119
mph1 km/h = 0.62137119 mph
Quick to:
1 km/h in all units
| Meters per second | 0.27777778 | m/s |
| Centimeters per second | 27.777778 | cm/s |
| Feet per second | 0.91134442 | ft/s |
| Miles per hour | 0.62137119 | mph |
| Knots | 0.5399568 | kn |
| Mach (at sea level) | 0.00081629721 | Ma |
| Speed of light | 9.265669e-10 | c |
About speed conversion
Speed measures distance over time. Different domains use different scales: cars in km/h or mph, ships and aircraft in knots, physics in m/s. This converter handles them all with full double-precision math.
Imperial speed units
Miles per hour (mph) is standard in the United States and the United Kingdom for road speeds. Feet per second (ft/s) appears in physics problems and ballistics. 1 mph ≈ 1.609 km/h.
Knots
A knot is one nautical mile per hour (1.852 km/h), used in marine and aeronautical navigation. The name comes from old log-line measurements, where knots in a rope were counted as it spooled overboard.
Mach & speed of light
Mach is a ratio relative to the local speed of sound (≈340 m/s at sea level). The speed of light, c, is exactly 299,792,458 m/s — the universal speed limit and a defining constant in SI.
Frequently asked questions
- How do I convert km/h to mph?
- Divide the km/h value by 1.609344. For example, 100 km/h ≈ 62.137 mph. The converter handles this instantly with full precision.
- How fast is one knot?
- One knot equals one nautical mile per hour, or exactly 1.852 km/h (about 1.151 mph). Knots are the standard unit in marine and air navigation.
- What is Mach 1?
- Mach 1 is the speed of sound. At sea level in dry air at 15°C it's about 340.29 m/s, or 1,225 km/h (761 mph). The actual value depends on air temperature and pressure.
- How fast is the speed of light?
- Light travels at exactly 299,792,458 m/s in a vacuum — about 1.079 billion km/h. It's the universal speed limit in physics and the basis of the SI definition of the meter.