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The calculator takes the distance of a run or race you completed and the time it took, both entered as simple numbers. It converts the distance to kilometres if you entered miles, then divides total minutes by kilometres to get your pace in min/km. It multiplies that by 1.60934 for min/mi, and computes speed as 60 divided by the pace. For the predictions, it applies the Riegel formula T2 = T1 × (D2 / D1)¹.06 to your known run: it treats your input as T1 and D1, then predicts T2 for 5K, 10K, half marathon (21.0975 km) and full marathon (42.195 km). The 1.06 exponent models the natural slowing of pace over longer distances, so predictions always show a slightly slower per-kilometre pace for longer races. These are estimates for planning and training, not medical advice. Always build fitness gradually and stop if you feel pain or dizziness.
Running pace is the time it takes you to cover a fixed distance, usually shown as minutes per kilometre (min/km) or minutes per mile (min/mi). It is the number most runners plan their training and races around, because it tells you exactly when you will reach each kilometre or mile marker. Speed is the inverse idea: distance covered per unit of time, shown as km/h or mph. A faster runner has a lower pace number but a higher speed number. In most countries outside the US, pace in min/km is the standard unit; in the US, min/mi is more common. This calculator shows both, so you can use whichever your training plan uses.
Enter the distance of a run or race you have completed, plus the time it took, and choose whether the distance is in kilometres or miles. The calculator instantly returns your average pace in min/km and min/mi, your speed in km/h and mph, and race-time predictions for 5K, 10K, half marathon and full marathon based on that performance. Use it before a race to find the pace a goal time requires, or after a run to see what your result predicts for longer distances. The inputs are large, full-width and touch friendly, and results update with one tap. This page works as a min/km to min/mile converter and a race time predictor in one.
Pace per km = total time in minutes / distance in km | Pace per mile = pace per km × 1.60934 | Pace per mile (from total time) = total time in minutes / distance in miles | Speed (km/h) = 60 / pace in min/km | Speed (mph) = 60 / pace in min/mile | Riegel race prediction: T2 = T1 × (D2 / D1)¹.06, where T1 and D1 are your known time and distance, and D2 is the target distance. The 1.06 exponent models how pace naturally slows as race distance grows.
Once you have a recent race result, you can estimate your finish time at other distances with the Riegel formula, published by Pete Riegel in 1977: T2 = T1 × (D2 / D1)¹.06. The exponent 1.06 accounts for the fatigue that slows you over longer races, so a marathon prediction is always a bit slower than simply scaling your 5K pace up. The calculator applies this formula to your input run and predicts your 5K, 10K, half marathon and full marathon times. Predictions are most accurate when your input was a recent maximum-effort race and the target distance is within a few multiples of it. A handy shortcut from runners: your marathon time is roughly your 5K time multiplied by 9.6. Enter any recent result, for example a 5K time, to predict your marathon time and other distances.
A 5K run in 25 minutes means a pace of 25 / 5 = 5:00 min/km, which converts to 8:03 min/mi and equals 12.0 km/h. The Riegel formula predicts from that 25:00 5K: a 10K in about 52 minutes, a half marathon in about 1 hour 55 minutes, and a marathon in about 4 hours. A 10K run in 50:00 gives the same 5:00 min/km pace and predicts a marathon of about 3 hours 50 minutes. A classic benchmark: a sub-4 hour marathon requires an average pace of 5:41 min/km (9:09 min/mi), which is about 10.55 km/h. These are even-split targets; real races with hills, heat or crowds will vary.
Even pacing is the most efficient race strategy for 5K and longer: the same pace every kilometre. Many runners instead aim for a negative split, running the second half slightly faster than the first, which research shows can improve times by 1 to 2 percent. Beginners typically run comfortably at 6:30 to 8:00 min/km, where conversation is possible (the talk test). Avoid the most common error: starting 10 seconds per kilometre too fast, which can cost several minutes over a marathon. Build a small buffer into the plan instead of chasing lost seconds after a slow first kilometre. As a quick running pace chart reference: 5:00/km gives a 25:00 5K, a 50:00 10K, a 1:45:00 half marathon and about a 3:31:00 marathon. Both even splits and negative splits start from these even-split targets, which you adjust into your race-day plan.
The classic mix-up is pace versus speed: pace is time per distance, speed is distance per time, and they are inverses. Do not include warm-up or cool-down walking in your race time, or your calculated pace will look slower than your true running pace. Another frequent mistake is running easy days too fast: most training should feel conversational. Finally, remember the calculator assumes flat conditions; add roughly 10 to 30 seconds per kilometre for heat or humidity and 5 to 20 seconds for hills.
Build your aerobic base with 70 to 80 percent of weekly mileage at an easy, conversational pace. Add one tempo run and one interval session per week, plus a weekly long run, to push your sustainable pace down over time. Strength training improves running economy, and a cadence around 170 to 180 steps per minute reduces injury risk. Track progress by timing a standard distance such as a 5K every few weeks and watching your pace improve with consistent training.
Divide your total running time in minutes by the distance you covered. For example, running 5 km in 25 minutes gives a pace of 25 / 5 = 5:00 min/km. Enter those two numbers here and the calculator also converts the result to min/mi and speed automatically.
Pace is time per distance, for example 5:00 min/km, and tells you how long each kilometre takes. Speed is distance per time, for example 12 km/h, and tells you how far you travel in an hour. They are inverses of each other: a faster runner has a lower pace but a higher speed.
Multiply your min/km pace by 1.60934 to get min/mi. For example, 5:00 min/km × 1.60934 = 8:03 min/mi. To convert the other way, divide min/mi by 1.60934, so 7:00 min/mi = 4:21 min/km. The calculator performs this conversion automatically.
A sub-4 hour marathon requires an average pace of 5:41 min/km or 9:09 min/mi over 42.195 km, which is about 10.55 km/h. Enter 42.195 km and 4:00:00 in the calculator to see the exact pace and the Riegel predictions for other distances.
A comfortable beginner pace is typically 6:30 to 8:00 min/km (10:30 to 12:50 min/mi). The right pace is one where you can hold a conversation without gasping, sometimes called the talk test. A typical beginner 5K time is 30 to 40 minutes.
Typically within 2 to 5 percent if your input was a recent maximum-effort race and you are properly trained for the target distance. The Riegel formula assumes similar conditions and training; first-time marathoners often run 10 to 15 percent slower than the prediction from a 5K, because marathon-specific endurance needs dedicated training.
The Riegel formula predicts your finish time at one distance from a known result at another: T2 = T1 × (D2 / D1)¹.06. T1 and D1 are your known time and distance, D2 is the target distance, and the 1.06 exponent models how pace slows as races get longer. It was published by Pete Riegel in 1977 and is the standard method behind most race predictors.
Use whichever is standard in your country: the US uses miles, most other countries use kilometres. The calculator accepts both and shows results in min/km, min/mi, km/h and mph, so your choice never limits you.