Speed Calculator
0 mph
| Unit | Speed |
|---|---|
| Miles per hour (mph) | |
| Kilometers per hour (km/h) | |
| Meters per second (m/s) | |
| Feet per second (ft/s) | |
| Knots (nautical mph) |
The Formula: Speed Equals Distance Over Time
This calculator uses the basic kinematic definition of average speed, speed = distance ÷ time. It converts whatever distance unit and hours/minutes/seconds you enter into a common base (meters and seconds), divides to get meters per second, and then converts that single result into miles per hour, kilometers per hour, feet per second, and knots so you can read off whichever unit you need. Because it's an average, it doesn't account for acceleration or variation during the trip — entering a 2-hour drive that included stoplights and highway stretches gives you the average speed over the whole trip, not your speed at any one moment.
Nautical Miles and Knots Use a Different Mile
A nautical mile (1,852 meters by international definition) is longer than a standard statute mile (1,609.34 meters), because it's historically based on one minute of latitude along a great circle rather than any land-survey distance. A "knot" is simply one nautical mile per hour — it is already a speed, so saying "knots per hour" is a common but redundant mistake. This calculator treats the knots row as nautical miles per hour for consistency with the other unit rows.
Related Tools
If you want to convert a single distance or time value on its own rather than compute a speed, the conversion calculator handles that directly. For working out fuel usage over a trip instead of speed, see the gas mileage calculator.
Frequently Asked Questions
How do I calculate average speed?
Divide total distance traveled by total time taken: speed = distance / time. This calculator converts your distance and time inputs into meters and seconds internally, computes meters per second, then converts that into mph, km/h, ft/s, and knots so you can read whichever unit you need.
Why is my calculated speed different from my car's speedometer reading?
This calculator gives average speed over the whole distance and time you enter, while a speedometer shows instantaneous speed at one moment. If you sped up, slowed down, or stopped during the trip, the average will differ from any single speedometer reading, and often from the highest speed you actually reached.