Running Pace Calculator

Enter any two of distance, time, or pace and it computes the missing value plus speed in km/h, mph, and m/s. Generates a split table at standard race checkpoints.

T2 = T1 x (D2/D1)^1.06 — extrapolates a finish time at a target distance from a known race. Most accurate when the two distances are within a factor of 4.

Distance in km, miles, meters, yards. Pace in min/sec per km or per mile. Outputs show metric and imperial side by side.

Yes, the Running Pace Calculator is 100% free with no registration, no hidden fees, and no usage limits. All processing happens locally in your browser, ensuring complete privacy.

Absolutely. The Running Pace Calculator processes everything client-side in your browser. No data is uploaded to or stored on any server. Your content remains private on your device at all times.

Yes, the Running Pace Calculator is fully responsive and works on smartphones and tablets. You can use it on any device with a modern web browser -- no app download required.

No account or registration is needed. Simply open the Running Pace Calculator in your browser and start using it immediately. There are no sign-up walls or usage restrictions.

Simply enter your input in the provided field, adjust any settings to your preference, and the tool will process it instantly. You can then copy the result to your clipboard or download it.

The Running Pace Calculator works in all modern browsers including Chrome, Firefox, Safari, Edge, and Opera. For the best experience, use the latest version of your preferred browser.

A sub-4-hour marathon means covering all 42.195 km in under 240 minutes, which works out to roughly 5:41 per kilometre, or about 9:09 per mile, held steadily from start to finish. That is a speed of around 10.5 km/h. The hard part is consistency: drift just 10 seconds per kilometre too slow and you finish several minutes over four hours, so most runners aim for an even or slightly negative split rather than banking time early. To plan it, use Calculate Time mode by entering 42.195 km and your goal pace, or Calculate Pace mode by entering the distance and a 3:59:59 target. The split table then shows the exact cumulative time you should hit at 5K, 10K, the half, and beyond, so you can check your watch against the plan during the race.

One mile is 1.60934 kilometres, so to convert a per-mile pace to per-kilometre you divide it by 1.60934, and to go the other way you multiply. For example, 8:00 per mile is about 4:58 per kilometre, and 5:00 per kilometre is roughly 8:03 per mile. Doing this in your head is error-prone because pace is in minutes and seconds rather than decimal minutes, so a single conversion mistake can throw off a whole race plan. This calculator removes the guesswork: every result displays pace in both minutes per kilometre and minutes per mile side by side, along with speed in km/h, mph, and m/s. Just enter your distance and time in whichever units you train in, and read the equivalent pace in the other unit directly, with no manual arithmetic.

The Riegel formula, T2 = T1 x (D2/D1)^1.06, is most reliable when your known race and your target are within a factor of about four of each other and you are equally trained for both distances. Predicting a half marathon from a 10K result usually lands close, because the gap is small and both reward similar endurance. Predicting a full marathon from a single fast 5K tends to look optimistic, since the 5K rewards speed while the marathon punishes any pacing or fuelling error over 42.195 km, plus the exponent assumes endurance-specific training you may not have. Treat a marathon projection as a best-case ceiling and shade your goal slightly slower. Enter your most recent comparable race here and the predictor returns equivalent 5K, 10K, half, and marathon times with the pace each implies.

Pace fades over distance because the body cannot sustain its short-distance power indefinitely. A 5K leans heavily on speed and your anaerobic capacity, while a marathon is governed by aerobic endurance, glycogen stores, and fatigue resistance, so the longer you run, the lower the pace you can hold. The Riegel formula captures this with its exponent of 1.06: if pace stayed identical the exponent would be exactly 1.0, and the slightly higher value mathematically slows your predicted pace as distance grows. That is why a runner who races 5K at 4:30 per kilometre will average noticeably slower over a half or full marathon. This calculator builds that slowdown into its race-time predictions, so the equivalent times it shows reflect realistic endurance decay rather than assuming you hold one pace forever.

To find distance from a pace and a duration, you divide the time by the pace per unit: at 5:00 per kilometre for 40 minutes, you cover 8 kilometres, since 40 divided by 5 equals 8. At 5:30 per kilometre that same 40 minutes yields about 7.27 kilometres. Working this out by hand is fiddly because pace is in minutes and seconds rather than decimals, which is exactly why fixed-duration sessions like tempo runs are easy to misjudge. Use the Calculate Distance mode: enter your pace and the time, and the tool returns the distance in kilometres, miles, metres, or yards, plus your speed in km/h, mph, and m/s. It is ideal for planning a 40-minute tempo or any timed workout where you want to know in advance how much ground you will actually cover.