A speed converter moves a velocity between the units different worlds use: km/h on most road signs, mph in the US and UK, m/s in physics, knots at sea and in the air, and ft/s in some engineering. It works by converting your value into a base unit — metres per second — and back out. Because the underlying length and time units are defined exactly, every speed conversion is exact, not an approximation.
Reviewed: June 20, 2026 · Author: Naveen P N, Founder — AI Calculator · Verified against: exact length/time definitions, recomputed in code.
How the conversion works
Each unit equals a fixed number of metres per second: km/h is 1000 m over 3600 s (0.277778), mph is one mile (1609.344 m) over an hour, and a knot is one nautical mile (1852 m) over an hour. Multiply your value by the "from" factor to reach m/s, then divide by the "to" factor. The two everyday shortcuts fall right out: divide km/h by 3.6 for m/s, and multiply mph by 1.609344 for km/h.
Worked example — 100 km/h across the units
Scenario: convert 100 km/h (a common motorway speed) to other units.
100 km/h is 62.1371 mph, 27.7778 m/s and 53.9957 knots. The reverse cases are just as clean: 60 mph is 96.5606 km/h, 10 m/s is exactly 36 km/h, and 1 knot is 1.852 km/h. The converter shows all five units at once, so whether you're reading a foreign speed limit or sanity-checking a physics answer, the figure you need is there.
Frequently Asked Questions
× 1.609344. 60 mph = 96.5606 km/h.
÷ 3.6. 100 km/h = 27.7778 m/s; 36 km/h = 10 m/s.
One nautical mile per hour: 1 kn = 1.852 km/h = 1.15078 mph.
62.1371 mph (also 27.7778 m/s, 53.9957 kn).
Yes — mile, foot and nautical mile are exact in metres; hour is 3600 s.