How to use the Speed Converter
- Enter the speed you have.
- Choose the unit you are converting from and the unit you want.
- Read the converted speed and the exact conversion factor.
- Check the table for other common speeds in the same units.
Formula used
Result = Value × (m/s per source unit ÷ m/s per target unit). 1 mph = 0.44704 m/s exactly, 1 km/h = 0.27778 m/s and 1 knot = 1852 m per hour exactly.
Worked example
Here is the Speed Converter worked through with the example values shown above, so you can check each step by hand.
| Inputs | |
|---|---|
| Value | 100 |
| From | Kilometres per hour (km/h) |
| To | Miles per hour (mph) |
| Result | |
| Converted value | 62.137119 |
| Conversion rate | 1 kmh = 0.62137119 mph |
Quick reference table
Common values converted with the units selected above.
| From | To |
|---|---|
| 10 kmh | 6.2137119 mph |
| 30 kmh | 18.641136 mph |
| 50 kmh | 31.06856 mph |
| 60 kmh | 37.282272 mph |
| 100 kmh | 62.137119 mph |
| 120 kmh | 74.564543 mph |
The key conversions
To convert km/h to mph, multiply by 0.621371. To convert mph to km/h, multiply by 1.609344. So 100 km/h is 62.14 mph, and 60 mph is 96.56 km/h.
One metre per second is 3.6 km/h, so you multiply m/s by 3.6 to get km/h. A speed of 10 m/s is 36 km/h, or 22.37 mph.
Speed limits in both systems
Common speed limits make useful reference points. 30 mph is 48 km/h, 50 mph is 80 km/h, 60 mph is 97 km/h and 70 mph is 113 km/h. In the other direction, 50 km/h is 31 mph, 100 km/h is 62 mph and 130 km/h is 81 mph.
If you drive in a country that uses a different unit, check that you are reading the speedometer scale for the right unit, and follow the posted limits.
Knots and aviation
A knot is one nautical mile per hour, and a nautical mile is exactly 1,852 metres, so one knot is exactly 1.852 km/h or about 1.151 mph. A ship travelling at 20 knots is going 37 km/h. Knots are used at sea and in the air because a nautical mile corresponds to one minute of latitude, which makes navigation easier.
A typical airliner cruising at 480 knots is going about 889 km/h.
Walking, running and sport
A brisk walking pace is around 5 to 6 km/h (about 3 to 3.7 mph). A runner holding 5:30 per kilometre is going 10.9 km/h. A fast sprinter can reach more than 10 m/s, which is over 36 km/h. For running pace in minutes per kilometre or mile, use the pace calculator on this site.
Feet per second appears in some engineering, ballistics and sports measurements. One foot per second is exactly 0.3048 m/s, about 1.097 km/h.
Everyday speeds for comparison
A brisk walk is about 5 km/h (3 mph), an easy bicycle ride is 15 to 20 km/h and city traffic often flows at 30 to 50 km/h. Motorway limits are commonly 100 to 130 km/h (62 to 81 mph). A commercial jet cruises at roughly 850 to 900 km/h, and sound travels through air at about 343 m/s, which is about 1,235 km/h, at 20 °C.
Light travels at 299,792,458 m/s, which is about 1.08 billion km/h. Use these values to get a feel for the numbers, and remember that stopping distances grow quickly with speed: doubling your speed roughly quadruples the braking distance.
Frequently asked questions
How do I convert km/h to mph?
Multiply by 0.621371. For example, 100 km/h is about 62.14 mph.
How do I convert mph to km/h?
Multiply by 1.609344. For example, 60 mph is about 96.56 km/h.
What is a knot?
One nautical mile per hour, which is exactly 1.852 km/h.
How do I convert m/s to km/h?
Multiply by 3.6. For example, 10 m/s is 36 km/h.
Is the conversion exact?
The mph, knot and ft/s factors are exact by definition. The result is shown to 8 significant digits.
What is Mach?
The speed of sound, which changes with temperature and altitude, so it is not a fixed number of km/h and is not included here.
How fast is 100 km/h in m/s?
About 27.8 m/s. Divide km/h by 3.6.
This calculator gives estimates for information only. Actual figures from a bank, employer, tax authority or doctor may differ. It is not financial, tax, legal or medical advice.