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Pace Calculator

Work out your running pace, finish time, or distance — just enter the two values you know. See your speed in km/h and mph, and get race-time predictions for 5K, 10K, the half marathon and the full marathon.

I want to calculate

Enter your distance and finish time to find your pace and speed.

Time

Understanding the Pace Calculator

The Pace Calculator turns any two of pace, time, and distance into the third — the core maths every runner needs. Pick what you want to find, enter the values you know in kilometres or miles, and it returns your pace in both minutes per kilometre and minutes per mile, your finish time, and your speed in km/h and mph. It also builds a race-time predictions table, showing what your current pace works out to over 5K, 10K, the half marathon, and the full marathon. Everything runs entirely in your browser with no sign-up, so you can plan training runs, goal-race splits, and treadmill sessions instantly and privately.

How it works

Choose whether to calculate pace, time, or distance, then fill in the two known values. The tool normalises your input to a single internal unit — seconds of pace per kilometre — so metric and imperial entries stay perfectly consistent. To find pace it divides your time by your distance; to find time it multiplies pace by distance; to find distance it divides time by pace. From the resulting pace it derives speed (3600 divided by seconds per km gives km/h) and converts to miles using the exact factor 1.609344. The race-time table simply multiplies your pace per kilometre by each standard race distance. Inputs are validated inline, so blank or zero values produce a friendly message rather than an error.

pace = time ÷ distance · time = pace × distance · distance = time ÷ pace. Speed (km/h) = 3600 ÷ (pace in seconds per km). Unit conversion: 1 mile = 1.609344 km. Race time = pace per km × race distance in km (5 km, 10 km, 21.0975 km half, 42.195 km marathon).

Worked example

Say you run 5 km in 25 minutes. Choose "Pace", enter 5 km and 0:25:00, and the calculator returns a pace of 5:00 per kilometre (about 8:03 per mile) and a speed of 12.00 km/h (7.46 mph). The predictions table then shows that holding 5:00/km would give roughly 50:00 for 10K, 1:45:29 for a half marathon, and 3:30:59 for a full marathon — handy for setting a realistic goal-race target before you commit to a training plan.

Tips & common mistakes

  • Time your pace over a flat, accurately measured route — GPS watches can read short or long on tree-lined or twisty courses.
  • Race predictions assume you hold an even pace the whole way; add a few percent for marathons, where late-race fatigue almost always slows you down.
  • Practise running at your goal pace in training so it feels controlled on race day rather than a surprise.
  • Use minutes per mile if you race in the US or UK road scene, and minutes per kilometre for track and most international events — the tool shows both.
  • Negative splits (running the second half slightly faster) usually beat going out too hard, so treat the predicted time as a ceiling, not a starting pace.
  • Re-check your pace as fitness improves; even a 10-second-per-km gain compounds into minutes over a half or full marathon.

Sources & methodology

  • • World Athletics – official road race distances (5 km, 10 km, half marathon 21.0975 km, marathon 42.195 km)
  • • Daniels' Running Formula (Jack Daniels) – pace and race-time relationships
  • • Road Runners Club of America – training pace and even-pacing guidance

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Reviewed by the TopOpenTools editorial team · Last updated June 2026. These tools provide general estimates for educational purposes only and are not financial, tax, insurance, investment, or medical advice. Verify important decisions with a qualified professional.

How to Use This Calculator

  1. 1Choose what to calculate — Pace, Time, or Distance.
  2. 2Enter the two values you know in km or miles, then click Calculate.
  3. 3Read your pace, speed, and race-time predictions — then plan fuelling with the calories burned calculator.

Frequently Asked Questions

How do I calculate running pace?

Pace is your time divided by the distance you covered. For example, running 5 km in 25 minutes gives a pace of 5:00 per kilometre. This calculator does the maths for you and also converts between minutes per kilometre and minutes per mile.

Can it predict my marathon time?

Yes. Once you enter a pace (or a recent run to derive one), the predictions table shows the finish time for 5K, 10K, the half marathon and the full marathon at that pace. The estimate assumes you hold an even pace, so allow some margin for fatigue over longer races.

Does it support both miles and kilometres?

Yes. You can enter distance in kilometres or miles and pace in minutes per kilometre or minutes per mile. Results always show pace and speed in both metric and imperial units, so you can read whichever you prefer.