Speed Converter
Turn any speed into a different unit — metric, imperial, or nautical — using exact international conversion factors.
Exact factors
Every conversion uses official international definitions — a mile is exactly 1609.344 m and a nautical mile exactly 1852 m — never a rounded guess.
Repeating decimals
Km/h and knots come from exact definitions but divide into repeating decimals, so results are rounded to six decimal places.
What is a speed converter?
One value, any unit
A speed converter changes a rate of travel from one unit into another — kilometres per hour to miles per hour, metres per second to km/h, knots to mph, and back. It works by translating every unit through a single shared base, the metre per second, so any pair of units can be converted with one consistent rule. This tool covers five common units across the metric, imperial, and nautical systems, making it useful for driving abroad, sailing, aviation, sports, physics homework, and anywhere speeds in different systems need to meet.
Each unit has an exact size in metres per second. To convert, the value is first turned into metres per second, then into the target unit.
Result = value × (m/s per from-unit) ÷ (m/s per to-unit)Because the conversion factors come from exact international definitions — mile = 1609.344 m, nautical mile = 1852 m, foot = 0.3048 m, and one hour = 3600 s — the result is mathematically faithful, limited only by how many decimal places are displayed. The same single rule handles every direction, so converting mph back to km/h just swaps which factor divides.
Suppose you want to convert 100 km/h into miles per hour.
Convert to the base unit
One km/h is 1000 m ÷ 3600 s = 0.277778 m/s, so 100 km/h = 27.7778 m/s.Divide by the target factor
One mph is 0.44704 m/s, so 27.7778 ÷ 0.44704 = 62.137119.Read the result
100 km/h converts to about 62.137119 mph.
The converted figure is as precise as the digits shown. Note that km/h and knots come from exact definitions — 1000/3600 and 1852/3600 metres per second — yet both produce repeating decimals, so the converter rounds results to six decimal places. For everyday tasks like checking a speed limit abroad or reading a boat's log, round the result to a sensible number of decimals; for physics or engineering work, keep the full precision. The knot, used in sea and air navigation, is slightly faster than 1 km/h, so a speed that looks modest in knots is a little larger than it first appears.
The arithmetic is faithful to the definitions; the only limit is display precision.
Rounding and unit choice
Because km/h and knots are repeating decimals, results are rounded to six decimal places, so the last digit may differ from an unrounded calculation. The converter handles steady speed only; it does not account for acceleration, wind, or current, which change real-world travel times. For navigation, motorsport, or scientific work, always confirm against the governing standard for your field.