Speed unit converter

Convert m/s, km/h, mph, knots, Mach and more.

Value Unit

m/s	-
km/h	-
mph	-
knot	-
ft/s	-
Mach (sea level)	-

Mach is an approximation based on standard atmosphere at sea level (about 343 m/s).

A rental car's dashboard reads in mph while the road signs are in km/h. A flight tracker shows ground speed in knots and a weather report gives wind in metres per second. Speed is one of those quantities everyone measures differently. Enter one value with its unit and the rest fill in at once.

How it works

How to use it

Enter a number in Value, pick its Unit, and the table below shows the same speed in m/s, km/h, mph, knots, ft/s and Mach. Any of the six can be the input, so it converts in every direction.

The conversion factors

Everything is converted through metres per second. All of these except Mach are exact definitions, not approximations:

Unit	In m/s
1 km/h	0.277778 (1000 ÷ 3600)
1 mph	0.44704
1 knot	0.514444 (1 nautical mile = 1,852 m per hour)
1 ft/s	0.3048

Two shortcuts worth remembering: km/h to m/s is a division by 3.6, and a knot is exactly 1.852 km/h — which is why a knot is very close to, but not the same as, a mile per hour.

Mach is the approximate one

Mach is a ratio to the local speed of sound, and the speed of sound depends on air temperature. This tool uses roughly 343 m/s, the value near sea level in ordinary conditions. Higher up, where the air is much colder, sound travels slower — around 295 m/s in the cruise altitudes of an airliner — so the same true airspeed corresponds to a higher Mach number up there. Treat the Mach column as a rough reference rather than a flight-grade figure.

A note on wind and vehicle speeds

Weather services typically report wind in m/s or knots, road traffic in km/h or mph, and marine and aviation traffic in knots. Confirm which unit a source is using before comparing two numbers — the gap between 30 knots and 30 km/h is large enough to matter.

Terms explained

m/s: Metres per second, the SI unit of speed and the value everything here converts through.
km/h: Kilometres per hour. Divide by 3.6 to get m/s.
mph: Miles per hour, based on the statute mile of 1,609.344 m. Used for road speeds in the US and UK.
Knot: One nautical mile per hour, exactly 1.852 km/h. Standard in aviation and at sea.
ft/s: Feet per second, where one foot is exactly 0.3048 m. Common in US engineering contexts.
Mach: A speed expressed as a multiple of the local speed of sound. Mach 1 here assumes about 343 m/s near sea level.

Frequently asked questions

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

Divide by 3.6. A kilometre is 1,000 metres and an hour is 3,600 seconds, so 1 km/h equals 1000 ÷ 3600, about 0.2778 m/s. Going the other way, multiply m/s by 3.6.

How fast is one knot?

Exactly 1.852 km/h, or about 1.15 mph, since a knot is one nautical mile per hour and a nautical mile is defined as 1,852 metres. That closeness to mph is why the two are easy to confuse in reports.

Is Mach 1 always the same speed?

No. Mach compares a speed to the local speed of sound, which falls as air temperature drops. Near sea level it is roughly 343 m/s, but at airliner cruise altitude it is closer to 295 m/s. This converter assumes the sea-level value.

Why does 60 mph not come out as exactly 96 km/h?

Because a mile is 1,609.344 m, so 60 mph is 96.56 km/h. The familiar "60 mph is about 96 km/h" is a rounded figure; this tool applies the exact factor, so small differences from mental estimates are expected.

Which unit is used for wind speed?

It varies by country and service — metres per second and knots are both common in meteorology, while km/h appears in general forecasts. Check the unit on the source before comparing two wind figures.