Pace Calculator

Solve for any one of pace, time, or distance from the other two — and see your speed in km/h and mph at the same time. Pick a race preset, toggle km or miles, and read the answer instantly. No sign-up; everything runs in your browser.

What is the Pace Calculator?

The pace calculator is a free running tool that links three numbers — your distance, your time, and your pace — and works out whichever one you are missing. Leave any single field blank and it fills it in: enter a distance and a finish time to discover your pace, enter a pace and a distance to predict a finish time, or enter a pace and a time to see how far that effort carries you. Alongside the answer it also reports your speed in km/h and mph, so you instantly see the same effort from both the runner's view (minutes per kilometer or mile) and the dashboard view (kilometers or miles per hour).

How to use it

Choose your unit toggle: kilometers or miles. Distance and pace follow that choice; results are still shown in both systems.
Fill in any two of the three fields — distance, time (hh:mm:ss), and pace (mm:ss per unit).
Leave the field you want to find empty and read the result the moment you stop typing — there is no Calculate button.
In a hurry? Tap a race preset (5K, 10K, half marathon, or marathon) to load the distance for you.

That is the whole flow: pick a unit, enter two numbers, read the third, and close the tab.

The formula and method behind it

Everything rests on one relationship:

pace = time / distance

which rearranges into time = pace x distance and distance = time / pace. Speed is the same effort flipped over:

speed = distance / time

The tool converts your inputs to a common base (kilometers and seconds), solves for the missing quantity, then converts back. The mile uses its exact definition of 1 mile = 1.609344 km, so metric and imperial results agree to the second. The standard race distances are 5K = 5 km, 10K = 10 km, half marathon = 21.0975 km, and marathon = 42.195 km.

Examples

Find pace: 10 km in 50:00 → 50 ÷ 10 = 5:00 per km (about 8:03 per mile, 12.0 km/h).
Find finish time: a marathon (42.195 km) at 6:00 per km → 4:13:10.
Find distance: running 5:30 per km for 45:00 → 45 ÷ 5.5 = 8.18 km.

Common use cases

Setting a goal pace for an upcoming 5K, 10K, half marathon, or full marathon.
Converting a treadmill speed into a real-world per-mile or per-kilometer pace.
Checking whether your training run hit the target effort.
Predicting a finish time so you can pick the right start corral or pacer.
Translating a coach's pace prescription between minutes per kilometer and minutes per mile.

Why use this one

Many pace pages only solve for pace, force you to pick a single unit, or hide the answer behind a button. This one is a true three-way solver: distance, time, or pace — leave any one blank and it computes it live. It carries one-tap race presets, a km/mi toggle, and a parallel speed readout in km/h and mph, so you never have to convert by hand. And it is completely private: every calculation runs in your browser, nothing you type is uploaded, and there is no account or app to install.

Frequently asked questions

How do I calculate my running pace?

Pace is your total time divided by the distance you ran. Enter the distance and the finish time, leave the pace field blank, and the calculator returns your pace per kilometer and per mile. For example, 10 km in 50 minutes is a 5:00 per km pace.

Can it work out my finish time for a race?

Yes. Pick a race preset like the marathon or type a distance, enter your target pace, and leave the time field blank. The tool multiplies pace by distance to predict your finish time, so you can plan a goal time before race day.

What is the difference between pace and speed?

Pace is time per distance (for example 5:00 per km) and goes down as you get faster, while speed is distance per time (for example 12 km/h) and goes up as you get faster. This calculator shows both at once, in km/h and mph.

Can I switch between kilometers and miles?

Yes. A single unit toggle switches the distance and pace between metric and imperial, and the results always display pace and speed in both systems so nothing gets lost in translation.

Is my data sent anywhere?

No. Every calculation runs entirely in your browser using plain JavaScript. Your distances and times are never uploaded, stored, or shared, and the tool keeps working after the page has loaded.