Speed Converter

How to use it

Speed conversions here run through meters per second, the SI unit, as the base. Multiplying by 3,600 (seconds per hour) and dividing by 1,000 (meters per kilometer) gives the shortcut everyone half-remembers: 1 m/s = 3.6 km/h exactly. So 10 m/s — a fast sprint pace — is 36 km/h. Miles per hour and kilometers per hour are both units of distance-over-time, just with different distance units: 1 mph equals exactly 1.609344 km/h, the same conversion factor as the mile itself, since the 'per hour' part doesn't change. A highway speed of 65 mph converts to 65 × 1.609344 ≈ 104.6 km/h — useful to know before driving in a country that posts speed limits in the other unit. Knots are different again: 1 knot is 1 nautical mile per hour, and a nautical mile (1,852 meters) is based on one minute of latitude, not the standard mile. That makes 1 knot equal to exactly 1.852 km/h, or about 1.151 mph. Knots are the standard unit for maritime and aviation speed because a vessel's speed in knots directly relates to how many minutes of latitude it covers — 1 nautical mile per hour was historically convenient for navigation with a map and a clock, before GPS. A rough anchor for sanity-checking results: walking pace is about 1.4 m/s (5 km/h, 3.1 mph), a car on a city street is often 13-18 m/s (50-65 km/h), and commercial jets cruise around 250 m/s (900 km/h, 486 knots). If a converted speed lands far outside a plausible range for its context, check whether you picked the right units before trusting the number.

Frequently asked questions

How do I convert km/h to mph quickly?

Multiply km/h by 0.6214, or roughly divide by 1.6. For a fast mental estimate, multiply by 0.6 — 100 km/h is close to 62 mph (the precise answer is 62.14 mph). For anything safety-related, like reading a foreign speed limit, use the exact conversion, not the shortcut.

Why do ships and planes use knots instead of mph or km/h?

A knot equals 1 nautical mile per hour, and a nautical mile is defined as one minute of latitude — a unit tied directly to navigation charts and the Earth's geometry. That made manual position-and-speed calculations easier long before GPS, and the convention has stuck in maritime and aviation use.

Is a nautical mile longer than a regular mile?

Yes. A nautical mile is 1,852 meters, versus 1,609.344 meters for a standard (statute) mile — about 15% longer. That's why 1 knot (1.852 km/h) is a slightly higher speed than 1 mph (1.609 km/h) even though both describe 'one mile per hour' in their respective systems.

What's a simple way to remember the m/s to km/h conversion?

Multiply by 3.6. It comes directly from unit arithmetic: there are 3,600 seconds in an hour and 1,000 meters in a kilometer, so m/s × 3,600 ÷ 1,000 simplifies to m/s × 3.6. It's exact, not an approximation, so you can rely on it without a calculator.