How do I convert m/s to km/h?

Multiply by 3.6. There are 3,600 seconds in an hour and 1,000 metres in a kilometre, so the factor is 3600/1000 — one of the few conversions worth memorising.

How fast is a knot in mph?

1.15078 mph, or 1.852 km/h exactly. A knot is one nautical mile per hour, and the nautical mile is defined as 1,852 metres.

What is 100 km/h in mph?

62.14 mph. The reverse — 60 mph — is 96.6 km/h, which is why 100 km/h and 60 mph are commonly treated as roughly equivalent motorway speeds.

Why do ships and aircraft use knots?

Because a nautical mile is about one minute of latitude, so speed in knots translates directly to progress across a chart. It is a navigational convenience that no metric unit replaces.

What is the speed of sound in these units?

About 343 m/s at 20°C, which is 1,235 km/h or 767 mph. It varies with temperature — sound travels faster in warmer air — which is why aviation figures always state conditions.

Speed Converter

Convert km/h, mph, knots, feet per second and metres per second.

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About the Speed Converter

Convert between mph, km/h, m/s, knots and more in one place. Values update as you type, and the result is calculated by converting to a base unit and back — so the arithmetic is the same in both directions and round-tripping a number returns exactly what you started with.

The conversions people need most are mph to km/h for driving abroad and m/s to km/h for physics. The second is easy once you see it: multiplying metres per second by 3.6 gives kilometres per hour, because there are 3,600 seconds in an hour and 1,000 metres in a kilometre.

Knots exist for the same reason nautical miles do. A knot is one nautical mile per hour, and since a nautical mile approximates one minute of latitude, a vessel making 10 knots covers 10 minutes of latitude per hour — which is directly readable off a chart.

How it works

Type a value and choose the units to convert between.
The result updates as you type, with the same value shown in every other unit below.
Jump straight to a direct page for the common conversions listed at the bottom.

Frequently asked questions

How do I convert m/s to km/h?: Multiply by 3.6. There are 3,600 seconds in an hour and 1,000 metres in a kilometre, so the factor is 3600/1000 — one of the few conversions worth memorising.
How fast is a knot in mph?: 1.15078 mph, or 1.852 km/h exactly. A knot is one nautical mile per hour, and the nautical mile is defined as 1,852 metres.
What is 100 km/h in mph?: 62.14 mph. The reverse — 60 mph — is 96.6 km/h, which is why 100 km/h and 60 mph are commonly treated as roughly equivalent motorway speeds.
Why do ships and aircraft use knots?: Because a nautical mile is about one minute of latitude, so speed in knots translates directly to progress across a chart. It is a navigational convenience that no metric unit replaces.
What is the speed of sound in these units?: About 343 m/s at 20°C, which is 1,235 km/h or 767 mph. It varies with temperature — sound travels faster in warmer air — which is why aviation figures always state conditions.

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