Speed, Distance & Time Calculator

About this tool

Solve for speed, distance, or time using the classic formula speed = distance ÷ time. Pick which value you want to solve for, fill in the other two, and get an instant result — handy for physics homework, trip planning, or pace calculations.

The one formula, three ways. Speed, distance, and time are locked together by speed = distance ÷ time, which rearranges into distance = speed × time or time = distance ÷ speed depending on which value is unknown. This tool doesn't do anything more advanced than that — it just picks the right rearrangement automatically based on which field you're solving for, so you never have to rearrange the algebra by hand.

Worked example. A 100 km trip taking 2 hours: speed = 100 ÷ 2 = 50 km/h. Going the other direction — traveling at 50 km/h for 2 hours covers 50 × 2 = 100 km. And at 50 km/h, covering 100 km takes 100 ÷ 50 = 2 hours. All three are the same underlying relationship, just solved for a different unknown.

The chart. Below the result, a distance-over-time line plots exactly this relationship visually: a straight line from the origin, whose slope is the speed — a steeper line means faster travel, and hovering anywhere along it reads off the distance covered by that point in time.

Units. Everything here is kilometers, hours, and km/h, chosen for consistency across the three fields — if your numbers are in miles, minutes, or another unit, convert them to km/h and hours first (or work entirely in whatever consistent unit system you prefer, since the arithmetic itself doesn't care what the units are called, only that all three fields agree).

Why time can't be zero, and speed matters more than it looks. Solving for time when speed is entered as zero would mean "how long to cover a distance while not moving," which has no finite answer — the tool flags this rather than showing a meaningless result. The same logic applies in reverse: solving for speed with a time of zero is equally undefined.

Common uses: checking a trip's expected drive time before leaving, working backward from an arrival deadline to the average speed needed, physics and school homework on uniform (constant-speed) motion, and sanity-checking a claimed speed or pace against a known distance and time.

For running or walking pace specifically (time per distance rather than distance per time), see the pace calculator. For converting between unit systems first, the unit converter.

Frequently asked questions

What units does this use?

Kilometers, hours, and km/h throughout, for consistency — convert your inputs to these units first if they're in miles, minutes, or another unit.

How is "time" solved for?

Using time = distance ÷ speed, the rearranged form of the same core formula.

What if I enter a speed of zero when solving for time?

The result shows a hint instead of a calculation, since dividing by zero speed would mean infinite time — not a meaningful answer.

Does this account for acceleration or stops along the way?

No — this is uniform (constant-speed) motion only. A real trip with stops, traffic, or varying speed only matches this formula for its average speed over the whole distance and time, not the speed at any one moment.

What does the slope of the chart line represent?

The speed itself — since distance = speed × time, the line's steepness (rise over run) is exactly the speed value, plotted visually rather than just as a number.

Can I use this for a pace in minutes per kilometer instead of km/h?

Not directly — this solves for speed as distance per hour. For a running or walking pace expressed as time per distance, the dedicated pace calculator is built for that exact framing.

Does it work for very small or very large numbers, like light-speed physics problems?

The arithmetic itself works for any positive numbers you enter — it's the same formula whether the units represent a walk to the shop or a homework problem with astronomical distances, as long as you're consistent with what "distance" and "time" mean in your problem.