How fast
are you going?

About the speed calculator

This calculator works with the three quantities of steady motion — distance, speed and time — and lets you solve for whichever one you do not know. Pick the target at the top, enter the other two, and the answer updates instantly. It is the everyday version of the physics relationship that connects how far something travels, how fast it moves, and how long the journey lasts.

How to use it

Choose what you want to find with the “Solve for” menu. To get average speed, leave it on Speed and enter the distance and the time: 100 km in 1.5 hours gives about 66.7 km/h. Switch to Distance to see how far you travel at a set speed for a set time, or to Time to find how long a trip takes at a given speed. Enter time in hours as a decimal, so half an hour is 0.5, and read the miles-per-hour equivalent beside the result.

The formula

All three answers come from one equation, $d = v \cdot t$, where $d$ is distance, $v$ is speed and $t$ is time. Rearranging it gives the other two forms, $v = \frac{d}{t}$ for speed and $t = \frac{d}{v}$ for time. Because each variable can be isolated on its own, knowing any two is always enough to work out the third — which is exactly what the “Solve for” switch does behind the scenes.

Where it is used

Drivers and cyclists use it to plan journey times and estimate arrival, runners use it to check pace over a known distance, and pilots and sailors use the same relationship for navigation. In physics classes it is the first step towards acceleration and motion problems. Anywhere something moves at a roughly steady rate — a delivery route, a train timetable, a treadmill workout — these three numbers are all you need.