Speed Calculator

Distance and time — speed, converted to whichever unit you need.

Speed
80.47 km/h

Speed = distance ÷ time — entered here as if "time" is in hours and the unit selector tells the calculator which distance unit you used.

A worked example

Traveling 100 miles in 2 hours works out to 50 mph — or about 80.5 km/h.

Frequently asked questions

What's a knot, and where is it used?

A knot is one nautical mile per hour, the standard speed unit in maritime and aviation contexts — it's based on nautical miles rather than standard miles, so it doesn't convert to mph with a simple round number.

Why does the distance unit matter here?

Speed is always distance over time, so the unit you pick determines how the raw number gets interpreted — entering 100 with 'mph' selected assumes the distance was measured in miles.