Speed Converter

1. 01Enter a value and its unitType the number and select which speed unit it is currently in.
2. 02Read the converted valuesEvery other supported unit updates automatically.
3. 03Enter a value of 0 or greaterThis tool treats speed as a non-negative magnitude, since direction is not part of a plain speed conversion.

• Converting a road speed limit or vehicle specConvert a speed limit or top-speed figure given in km/h to mph, or the reverse, when comparing specs between regions.
• Reading a wind or weather reportConvert wind speed between knots (common in marine and aviation forecasts), km/h, and mph.
• Working out a running or cycling paceConvert a speed in km/h or mph into m/s for pace or interval-training calculations.

• 100 km/h ≈ 62.14 mphA common highway speed of 100 km/h converts to approximately 62.14 miles per hour.
• 1 knot ≈ 1.15078 mphA knot (one nautical mile per hour) is slightly faster than one mile per hour — used in marine and aviation contexts rather than mph or km/h.
• 1 km/h = 5/18 m/s, exactlySince 1 km/h is defined as 1000 meters per 3600 seconds, the exact fraction 5/18 converts km/h to m/s with no rounding.

This tool uses exact, internationally defined constants: 1 km/h = 1000/3600 m/s = 5/18 m/s exactly; 1 mph = 1609.344 m (the exact international mile) / 3600 s = 0.44704 m/s exactly; and 1 knot = 1852 m (the exact international nautical mile) / 3600 s exactly. Every conversion is computed through one canonical internal unit (m/s) with no intermediate rounding, so chained or round-trip conversions do not drift.

A knot is one nautical mile per hour, and a nautical mile (1852 m) is longer than a statute/international mile (1609.344 m) — so a given number of knots is always a slightly higher speed than the same number expressed in mph. Knots are the standard unit in marine navigation and aviation, while mph and km/h are the common units on land.

Speed here is treated as a non-negative number — a magnitude, not a vector with direction. A negative input is rejected rather than converted, since a negative speed reading is not physically meaningful in this context (unlike, for example, a pressure-converter vacuum-gauge reading, which legitimately can be negative).

What is the exact km/h-to-m/s conversion?

1 km/h = 5/18 m/s exactly (about 0.277778 m/s), derived directly from 1000 meters per 3600 seconds — not a rounded approximation.

Is a knot the same as mph?

No. A knot (1 nautical mile per hour, based on the 1852 m international nautical mile) is about 15% faster than 1 mph (based on the 1609.344 m international mile).

Why does the tool reject negative speed values?

This converter treats speed as a non-negative magnitude, since a plain speed conversion has no concept of direction. A negative number would not represent a real speed reading here, so it is rejected rather than silently converted into a misleading result.

Which unit should I use for wind speed?

Knots are the standard for marine and aviation forecasts; km/h and mph are more common in general weather reporting. This tool shows all four units at once so you can read whichever one you need.

Is my data saved?

No. Everything is calculated in your browser; nothing is sent to a server.