Understanding Speed Conversions
Speed is distance per unit time — meters per second (m/s), kilometers per hour (km/h), miles per hour (mph), knots, and more. This converter supports over 30 units, from everyday (km/h, mph) to scientific (Mach, cosmic velocities, speed of light). Convert between any of them instantly.
How Speed Conversion Works
All speed units are defined relative to the meter per second (m/s), the SI unit. To convert between any two units, the value is first expressed in m/s, then divided by the target unit's m/s equivalent. The general formula is:
Result = Value × (source unit in m/s) ÷ (target unit in m/s)
For example, converting 100 km/h to mph: 100 × (1000/3600) ÷ (1609.344/3600) ≈ 62.14 mph. Speed units combine a length unit and a time unit — kilometer per hour, foot per second, nautical mile per hour (knot) — so conversion factors depend on both.
Key Speed Units Explained
The most common and scientifically important speed units, with their relationship to meters per second.
Meter/second (m/s)
Factor: 1 (base unit)
The SI unit of speed — one meter traveled per second. Used in physics, engineering, and weather (wind speed in some countries). 1 m/s = 3.6 km/h.
Kilometer/hour (km/h)
Factor: 1 km/h = 0.2778 m/s
The standard for road speed limits and vehicle speedometers outside the US. 1 km/h = 1000 m / 3600 s. To convert km/h to mph, multiply by 0.621371.
Mile/hour (mph)
Factor: 1 mph ≈ 0.44704 m/s
Used in the US, UK, and a few other countries for road speeds and wind. 1 mph = 1 statute mile (1609.344 m) per hour. To convert mph to km/h, multiply by 1.60934.
Knot (kt, kn)
Factor: 1 knot ≈ 0.5144 m/s
One nautical mile (1852 m) per hour. Used in aviation, maritime, and meteorology. 1 knot ≈ 1.15078 mph ≈ 1.852 km/h. Knot (UK) uses the UK nautical mile (1853.184 m).
Foot/second (ft/s)
Factor: 1 ft/s = 0.3048 m/s
Common in US engineering and ballistics. 1 ft/s = 0.6818 mph = 1.0973 km/h. Flow rates and projectile speeds are sometimes given in ft/s.
Mach (20°C, 1 atm)
Factor: 1 Mach ≈ 343.22 m/s
Speed of sound in dry air at 20°C and 1 atmosphere. Aircraft and missiles are often described in Mach number. Mach 1 ≈ 1235 km/h ≈ 767 mph. Varies with temperature and humidity.
Speed of light in vacuum
Factor: c = 299,792,458 m/s
The universal speed limit. Used in relativity and astronomy. 1 c ≈ 1.08 billion km/h. Cosmic and Earth velocities are much smaller but still huge compared to everyday speeds.
Cosmic velocities (first, second, third)
Factor: ~7910, ~11200, ~16670 m/s
First: orbital velocity at Earth's surface (~7.9 km/s). Second: escape velocity from Earth (~11.2 km/s). Third: escape from the solar system from Earth's orbit (~16.7 km/s). Used in astronautics.
Common Speed Conversions at a Glance
Reference for every unit in the calculator: each row shows how to convert that unit to a common reference (m/s or km/h). Use the tool above to convert between any pair.
| From | To | Formula | Example |
|---|---|---|---|
| Meter/second | Kilometer/hour | m/s × 3.6 | 10 m/s = 36 km/h |
| Kilometer/hour | Meter/second | km/h × 0.277778 | 36 km/h = 10 m/s |
| Mile/hour | Kilometer/hour | mph × 1.60934 | 60 mph = 96.56 km/h |
| Meter/hour | Meter/second | m/h ÷ 3600 | 3600 m/h = 1 m/s |
| Meter/minute | Meter/second | m/min ÷ 60 | 60 m/min = 1 m/s |
| Kilometer/minute | Kilometer/hour | km/min × 60 | 1 km/min = 60 km/h |
| Kilometer/second | Kilometer/hour | km/s × 3600 | 1 km/s = 3600 km/h |
| Centimeter/hour | Meter/second | cm/h ÷ 360000 | 360000 cm/h = 1 m/s |
| Centimeter/minute | Centimeter/second | cm/min ÷ 60 | 60 cm/min = 1 cm/s |
| Centimeter/second | Meter/second | cm/s ÷ 100 | 100 cm/s = 1 m/s |
| Millimeter/hour | Meter/second | mm/h ÷ 3.6e6 | 3.6e6 mm/h = 1 m/s |
| Millimeter/minute | Millimeter/second | mm/min ÷ 60 | 60 mm/min = 1 mm/s |
| Millimeter/second | Meter/second | mm/s ÷ 1000 | 1000 mm/s = 1 m/s |
| Foot/hour | Foot/second | ft/h ÷ 3600 | 3600 ft/h = 1 ft/s |
| Foot/minute | Foot/second | ft/min ÷ 60 | 60 ft/min = 1 ft/s |
| Foot/second | Meter/second | ft/s × 0.3048 | 1 ft/s = 0.3048 m/s |
| Yard/hour | Yard/second | yd/h ÷ 3600 | 3600 yd/h = 1 yd/s |
| Yard/minute | Yard/second | yd/min ÷ 60 | 60 yd/min = 1 yd/s |
| Yard/second | Meter/second | yd/s × 0.9144 | 1 yd/s = 0.9144 m/s |
| Mile/minute | Mile/hour | mi/min × 60 | 1 mi/min = 60 mph |
| Mile/second | Kilometer/hour | mi/s × 5793.64 | 1 mi/s = 5793.64 km/h |
| Knot | Kilometer/hour | knot × 1.852 | 10 kn = 18.52 km/h |
| Knot (UK) | Kilometer/hour | kt (UK) × 1.85318 | 10 kt (UK) = 18.53 km/h |
| Speed of light in vacuum | Kilometer/hour | c × 1.079e9 | 1 c = 1.08 billion km/h |
| Cosmic velocity - first | Kilometer/hour | × 28476 | 1 = 28,476 km/h |
| Cosmic velocity - second | Kilometer/hour | × 40320 | 1 = 40,320 km/h |
| Cosmic velocity - third | Kilometer/hour | × 60012 | 1 = 60,012 km/h |
| Earth's velocity | Kilometer/hour | × 107154 | 1 = 107,154 km/h |
| Velocity of sound in pure water | Meter/second | 1 = 1500 m/s | 1 = 1500 m/s |
| Velocity of sound in sea water (20°C, 10 m) | Meter/second | 1 = 1542.6 m/s | 1 = 1542.6 m/s |
| Mach (20°C, 1 atm) | Kilometer/hour | Mach × 1235.59 | Mach 1 = 1235.59 km/h |
| Mach (SI standard) | Kilometer/hour | Mach × 1225.04 | Mach 1 = 1225.04 km/h |
Why So Many Speed Units?
Speed is distance divided by time, so every combination of length unit (meter, mile, nautical mile, foot) and time unit (second, minute, hour) gives a valid speed unit. Different industries standardized on different pairs: roads use km/h or mph, aviation and marine use knots, physics uses m/s, and high-speed flight uses Mach number (multiples of the speed of sound).
This converter includes metric and imperial everyday units (m/s, km/h, mph, ft/s, yd/s, mi/min, etc.), nautical units (knot, knot UK), and scientific reference speeds (speed of light, cosmic velocities, Earth's orbital velocity, speed of sound in water and air). Use the dropdown to select any unit and convert to another.
Real-World Speed References
Approximate speeds to calibrate your intuition when converting km/h to mph or comparing units.
Walking & Running
- Walking: ~5 km/h (3.1 mph)
- Jogging: ~10 km/h (6.2 mph)
- Running (marathon pace): ~12 km/h (7.5 mph)
- Sprint (100 m): ~36 km/h (22 mph) peak
Road & Rail
- City speed limit: 50 km/h (31 mph) typical
- Highway: 100–120 km/h (62–75 mph)
- High-speed train: 250–350 km/h (155–217 mph)
Aviation & Maritime
- Ship (cruise): 20–25 knots (37–46 km/h)
- Commercial jet: ~800 km/h (497 mph, Mach 0.85)
- Speed of sound (sea level, 20°C): 1235 km/h (767 mph)
Science & Space
- Earth's orbital speed: ~107,000 km/h (66,600 mph)
- Escape velocity (Earth): ~40,300 km/h (25,000 mph)
- Speed of light: ~1.08 billion km/h
Speed Conversion FAQ
? How do you convert km/h to mph?
Multiply the speed in km/h by 0.621371 to get mph. For example, 100 km/h = 62.14 mph. To convert mph to km/h, multiply by 1.60934. This converter does the math for any pair of units.
? What is the difference between a knot and mph?
A knot is one nautical mile (1852 m) per hour. One knot ≈ 1.15078 mph ≈ 1.852 km/h. Knots are used in aviation, shipping, and meteorology (wind speed at sea). The UK knot uses a slightly different nautical mile (1853.184 m).
? How many km/h is Mach 1?
Mach 1 (speed of sound in air at 20°C and 1 atm) is approximately 343 m/s, or 1235 km/h (767 mph). The exact value depends on temperature, humidity, and pressure. At higher altitude (colder air), the speed of sound is lower.
? What are cosmic velocities?
First cosmic velocity (~7.9 km/s) is the orbital speed at Earth's surface. Second cosmic velocity (~11.2 km/s) is the escape velocity from Earth. Third cosmic velocity (~16.7 km/s) is the speed needed to leave the solar system from Earth's orbit. They are used in astronautics and orbital mechanics.