Speed Converter
Convert speed across six units, from everyday road speeds to knots and Mach.
All units
How to use the Speed Converter
- Enter the speed you want to convert.
- Select the units to convert from and to.
- The table below shows the same speed in every supported unit.
Common speed equivalents
| km/h | mph | m/s | Context |
|---|---|---|---|
| 5 | 3.1 | 1.4 | Walking pace |
| 30 | 18.6 | 8.3 | Urban speed limit in much of Europe |
| 50 | 31.1 | 13.9 | Typical city limit |
| 100 | 62.1 | 27.8 | Highway cruising |
| 120 | 74.6 | 33.3 | Motorway limit in many countries |
Two conversions worth memorising: multiply km/h by 0.62 for mph, and divide by 3.6 for m/s.
Knots and Mach
A knot is one nautical mile per hour — 1.852 km/h exactly. It persists in aviation and shipping because it maps cleanly onto latitude: one knot for one hour covers one minute of latitude on a chart. The name comes from the knotted line sailors once let out behind a ship to measure its speed.
Mach is not a fixed speed. It is a ratio against the local speed of sound, which depends on air temperature and therefore altitude. At sea level in standard conditions sound travels at about 340 m/s; at cruising altitude it is closer to 295 m/s. This converter uses the sea-level value, so treat Mach figures as indicative only.
Frequently asked questions
How do I convert km/h to m/s quickly?
Divide by 3.6. The factor comes from 1,000 metres per kilometre divided by 3,600 seconds per hour.
Is a knot the same as a mile per hour?
No. A knot is 1.15 mph, because it is based on the nautical mile of 1,852 metres rather than the statute mile of 1,609.
Why is Mach marked "at sea level"?
The speed of sound falls as air gets colder, so Mach 1 is a different speed at 10,000 metres than at ground level. A fixed conversion can only use one reference condition.
How do I convert a running pace?
Pace is time per distance, the inverse of speed. To convert 5 minutes per kilometre, divide 60 by 5 to get 12 km/h, then convert that.
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