Speed Distance Time Calculator

The speed distance time calculator is built on one of the most fundamental relationships in physics: speed equals distance divided by time (v = d/t). Rearrange this formula and you get the other two: distance equals speed multiplied by time (d = v × t), and time equals distance divided by speed (t = d/v).

This calculator lets you solve for any of the three variables. Select what you want to find using the buttons at the top, enter the two values you know, and the result appears instantly. All unit conversions — between mph, km/h, m/s, miles, kilometres, and more — happen automatically behind the scenes.

The speed distance time relationship applies everywhere: road trips, running pace calculations, physics homework, astronomy, and engineering. Understanding how to move between the three values is one of the most practical skills in applied mathematics.

Use the speed distance time calculator for trip planning (how long will this drive take?), running and cycling training (what pace do I need to run a 4-hour marathon?), physics homework (find the velocity given displacement and time), and any scenario where you know two of the three values and need the third.

For physics problems involving acceleration, use a kinematics calculator instead — this tool assumes constant speed throughout.

The most common mistake is mixing units — entering speed in mph and distance in kilometres without converting. This calculator handles that automatically, but when doing manual calculations always confirm your units match before dividing.

A second mistake is forgetting to convert time into a single unit. If your time is 1 hour 30 minutes, that is 1.5 hours — not 1.3 hours. The calculator accepts hours, minutes, and seconds separately to avoid this error.

Finally, these formulas assume constant speed. Real-world travel involves acceleration, stops, and speed changes. Results are best understood as averages over the total journey.

The core formula is v = d/t, where v is speed (or velocity for direction-aware problems), d is distance, and t is time.

To find speed: v = d ÷ t. Example: 300 km in 3 hours = 100 km/h. To find distance: d = v × t. Example: 100 km/h for 2.5 hours = 250 km. To find time: t = d ÷ v. Example: 150 km at 60 km/h = 2.5 hours.

Unit conversions used internally: 1 mph = 0.44704 m/s, 1 km/h = 0.27778 m/s, 1 mile = 1609.34 m, 1 km = 1000 m. All inputs are converted to SI units (metres and seconds) before calculation, then converted back to the selected output unit.