How is each unit converted?

Every input is first converted to metres per second using its exact factor, then out to every other unit. This single-base method avoids compounding rounding across chained conversions.

What value of Mach 1 is used?

Mach 1 here is 340.29 m/s, the speed of sound in dry air at 15 degrees Celsius (sea-level ISA standard atmosphere). Mach number falls with altitude and temperature, so this is a reference figure, not a universal constant.

How many m/s is one knot?

Exactly 0.514444 m/s. A knot is one nautical mile (1852 m) per hour, so 1852 divided by 3600 seconds gives 0.5144 m/s, or about 1.852 km/h.

What is the exact mph to km/h factor?

1 mile per hour equals exactly 1.609344 km/h, because a mile is defined as exactly 1609.344 metres. So 60 mph is 96.56 km/h.

Does this tool send my data anywhere?

No. All conversions run locally in your browser with JavaScript. Nothing is uploaded, logged or stored.

Speed Unit Conversion Reference

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Convert any speed unit in one place

Speed is distance over time, and the world uses many units for it: scientists use metres per second, drivers use km/h or mph, sailors and pilots use knots, and aerospace uses Mach number. This reference converts between all of them from a single input, plus shows the value as a fraction of the speed of light.

How it works

Every unit has an exact factor to the SI base, metres per second. Your input is converted to m/s first, then out to each target:

1 km/h   = 0.277778 m/s   (1000 / 3600)
1 mph    = 0.44704  m/s   (1609.344 / 3600)
1 knot   = 0.514444 m/s   (1852 / 3600)
1 ft/s   = 0.3048   m/s   (exact foot definition)
Mach 1   = 340.29   m/s   (dry air, 15 C, sea level ISA)
c        = 299792458 m/s  (speed of light, exact)

Converting through a single base avoids the error that builds up when you chain unit-to-unit factors one after another.

Tips and notes

Mach number depends on air temperature; the 340.29 m/s figure is sea-level standard only.
A handy mental check: 1 m/s is about 3.6 km/h and roughly 2.24 mph.
Knots and km/h are close: 1 knot is about 1.15 mph or 1.85 km/h.
The light-speed fraction is tiny for everyday speeds but useful for physics context.