Speed Converter
Convert between km/h, mph, metres per second, feet per second and knots.
The speed converter translates between the units used for road speed, wind, aviation and science. Kilometres per hour is standard in India and most countries, miles per hour in the UK and USA, while knots are used at sea and in the air.
How to use the converter
- Enter the speed value.
- Choose the from and to units.
- See the converted speed and the full table.
- Useful for reading vehicle specs, weather reports and flight data.
How the conversion works
Result = value in metres per second ÷ factor of the target unit
Worked example
100 km/h to mph
100 × 0.2777777778 = 27.7778 m/s, then ÷ 0.44704 = 62.14 mph
That is also about 54 knots.
Popular conversions
Jump straight to a single conversion, or use the converter above for any pair.
Who should use this speed converter
- Drivers and travellers reading speed limits or vehicle specifications in miles per hour when they think in kilometres per hour.
- Runners and cyclists comparing pace in minutes per kilometre with speed in kilometres per hour.
- Anyone reading weather or marine reports where wind speed is given in knots.
- Students working problems in physics, where metres per second is the unit that fits the equations.
Common mistakes to avoid
- Confusing pace with speed. They move in opposite directions: 6 minutes per kilometre is 10 km/h, but 6 miles per hour is 10 minutes per mile. Mixing them up makes a slow runner look fast.
- Using the wrong conversion factor between km/h and mph. Multiply by 0.6214 to go from km/h to mph. Dividing by 1.6 is a decent approximation, but rounding to 1.5 is a 7% error.
- Assuming a knot is the same as a mile per hour. A knot is one nautical mile per hour, or 1.852 km/h — noticeably faster than a statute mile per hour.
- Forgetting that speedometers over-read. Almost every car shows a speed a few percent above the true figure by design, so a GPS reading is usually closer to reality.
- Comparing acceleration with top speed. Zero to 100 km/h and top speed are different measurements, and one says little about the other.
Speed, pace and what the numbers mean
Speed measures distance covered per unit of time; pace measures time taken per unit of distance. The two are reciprocals, which is why a faster runner has a lower pace figure and a higher speed figure. Runners tend to use pace because it makes planning easier — if your pace is 6 minutes per kilometre, a 10 km run takes an hour.
For travel, the useful mental anchor is that 60 mph is about 96.5 km/h, so a 65 mph limit is roughly 105 km/h. Wind is reported in knots at sea because a knot is one minute of latitude per hour, which lines up neatly with nautical charts. Converting those figures into km/h makes weather warnings much easier to judge.
Speed units explained
- Kilometres per hour
- The standard road speed unit in India and most of the world. One km/h is 0.2778 metres per second.
- Miles per hour
- The road speed unit in the US and UK. One mph is 1.609 km/h.
- Knot
- One nautical mile per hour, or 1.852 km/h. Used in aviation and marine navigation.
- Metres per second
- The SI unit of speed, used in physics. Multiply by 3.6 to get km/h.
- Pace
- Time per unit distance, usually minutes per kilometre or per mile. The reciprocal of speed.
Speeds worth memorising
Once a handful of conversions are familiar, most situations need no calculation. In round numbers: 30 km/h is 18.6 mph, 50 km/h is 31 mph, 80 km/h is 50 mph, 100 km/h is 62 mph and 120 km/h is 75 mph. A 30 mph limit is 48 km/h and a 70 mph motorway limit is about 113 km/h.
Wind and marine speeds use knots, where one knot equals 1.852 km/h. So a 30-knot wind is about 55 km/h and a 50-knot gust is close to 93 km/h — the difference between a breezy day and a damaging one. Knowing that one knot is nearly two kilometres per hour makes weather warnings much easier to read quickly.
Frequently asked questions
How do I convert km/h to mph?
Multiply by 0.621371. So 100 km/h is about 62.14 mph. To convert mph to km/h, multiply by 1.609344 instead.
What is a knot?
A knot is one nautical mile per hour, equal to about 1.852 km/h or 0.514 metres per second. It is used for ships, aircraft and wind speeds at sea.
How do I convert m/s to km/h?
Multiply by 3.6. So 10 m/s is 36 km/h. This conversion is common when comparing scientific data with everyday speeds.