Speed converters
Speed converters for km/h, m/s, mph and knots, plus a practical speed, distance and time calculator.
Last updated: May 2026
Core speed tools
Speed values are shown in different units depending on the country, machine or type of task. Road speeds often use km/h or mph. Technical specs may use m/s. Marine and aviation contexts still use knots. Putting the right tool in one place saves time and avoids easy mistakes.
Where each speed unit is used
Speed is measured in different units depending on the industry and country. Road signs in the US and UK use mph; most of the rest of the world uses km/h. Physics and engineering often use m/s because it fits cleanly into SI formulas. Aviation and maritime navigation use knots, where one knot equals one nautical mile per hour. Knowing which unit a source is using prevents easy errors when comparing specs or reading reports.
| Context | Typical unit | Real-world example |
|---|---|---|
| Road speed (US, UK) | mph | Urban limit 30 mph = 48 km/h |
| Road speed (EU and most of world) | km/h | Motorway limit 120 km/h = 74.6 mph |
| Physics and engineering | m/s | 60 km/h = 16.7 m/s |
| Aviation and marine | knots | Cruising speed 480 kn = 889 km/h |
| Wind speed (weather) | km/h or knots | Strong breeze: 40 km/h = 21.6 kn |
| Running pace | min/km or min/mile | 5 min/km = 12 km/h = 7.5 mph |
Speed conversion factors
| Conversion | Multiply by | Example |
|---|---|---|
| km/h to mph | 0.6214 | 100 km/h = 62.1 mph |
| mph to km/h | 1.6093 | 60 mph = 96.6 km/h |
| m/s to km/h | 3.6 | 27 m/s = 97.2 km/h |
| km/h to m/s | 0.2778 | 50 km/h = 13.9 m/s |
| knots to km/h | 1.852 | 20 kn = 37 km/h |
When unit choice is not optional
Knots are not just a tradition. ICAO mandates that air traffic worldwide uses knots for airspeed and nautical miles for distance, so a pilot cannot simply choose km/h when filing a flight plan or reading instrument markings. The nautical mile is defined as one minute of latitude, which makes position reporting and navigation consistent across all countries. Ships use the same standard for the same reason.
Running pace is the speed unit most likely to cause confusion because it is the inverse of every other speed measure. Every other unit tells you distance per unit of time; pace tells you time per unit of distance. Faster pace is a lower number: a 4:30/km pace is faster than a 5:00/km pace, which is the opposite of how km/h or mph work. Converting between pace and speed requires the extra step of inverting the ratio (pace in min/km = 60 / speed in km/h), which is why runner's apps rarely show km/h directly.
GPS speed and car speedometers diverge deliberately. Regulators allow speedometers to over-read by up to 10 percent but prohibit under-reading, so manufacturers calibrate them to show slightly more than true speed. A GPS receiver measures actual distance over actual time and is typically within 1-2 km/h of true speed at road velocities. The gap is most visible on a motorway: a speedometer reading 110 km/h often corresponds to a GPS speed of 103-107 km/h. Neither is wrong; they measure different things.
Frequently Asked Questions
How do I convert m/s to km/h quickly?
Multiply by 3.6, because one metre per second equals 3.6 km/h. To reverse it, divide km/h by 3.6. So 27 m/s is 97.2 km/h, and 90 km/h is 25 m/s.
What is a knot and why is it different from km/h?
One knot is one nautical mile per hour, which is 1.852 km/h. Nautical miles are tied to lines of latitude, so knots stay standard for ships and aircraft worldwide regardless of the country.
What is a quick way to estimate km/h in mph?
Multiply km/h by 0.6, or take off roughly a third. 100 km/h is about 62 mph, and 50 km/h is about 31 mph. For the reverse, add about 60 percent to the mph figure.
Why does my GPS speed differ from the car speedometer?
Car speedometers are designed to read slightly high so they never under-report, while GPS measures actual distance over time and is usually closer to true speed. A few km/h difference is normal.
How do I get travel time from speed and distance?
Time equals distance divided by speed, kept in matching units. For 150 km at 100 km/h, that is 1.5 hours. The speed, distance and time calculator handles the arithmetic for you.
What speed is 100 km/h in mph?
100 km/h is 62.1 mph. A rough mental shortcut: multiply km/h by 0.6 for a close estimate. For the reverse, multiply mph by 1.6. Common check values: 50 km/h = 31 mph, 80 km/h = 49.7 mph, 110 km/h = 68.4 mph.
What is the speed of sound and how fast is that in km/h?
The speed of sound in dry air at 20 degrees C is about 343 m/s, which is 1235 km/h or 767 mph. Aircraft speed is sometimes expressed as a Mach number: Mach 1 is the speed of sound, Mach 2 is twice that (2470 km/h). The Mach value changes slightly with altitude and temperature.
How do I convert running pace to speed?
Divide 60 by your pace in minutes per km to get km/h. A pace of 5 min/km is 60 / 5 = 12 km/h. A pace of 6 min/km is 10 km/h. For miles, divide 60 by minutes per mile to get mph: 8 min/mile is 60 / 8 = 7.5 mph = 12.1 km/h.