Running Pace Calculator
Pace from a race time, plus Riegel predictions for 5K, 10K, half and marathon
100% free. Runs entirely in your browser - your files and data never leave your device and nothing is uploaded to any server.
If you held this fitness (Riegel 1.06)
Predictions assume similar conditions. Hills, heat and a different distance can move the time a lot.
Estimates only. Not medical advice and not a diagnosis. Talk to a clinician about your own numbers. Training advice is not a medical clearance to run.
About this tool
Pace is finish time divided by distance. Predictions for other distances use Riegel's formula with exponent 1.06: a 10K is a little slower than twice a 5K. Hills, heat, wind and a different training block will move the time. This is a training sketch, not a guaranteed race result and not a medical clearance to run. Estimates only.
How to use this tool
- Pick a distance or type custom kilometres5K, 10K, 15K, half, marathon and 1 mile are listed.
- Enter finish time as mm:ss or h:mm:ssExample: 22:30 or 1:45:00.
- Read min/km, min/mile and predicted timesUse predictions as a training sketch, not a race promise.
How to calculate running pace
Pace is your time divided by the distance. A 5K in 25 minutes is 25 / 5 = 5:00 per kilometre, or about 8:03 per mile. To turn pace per kilometre into pace per mile, multiply by 1.609.
To predict another distance, the calculator uses Riegel’s formula: new time = old time x (new distance / old distance) to the power 1.06. From a 25-minute 5K that predicts about 52 minutes for 10K - a little slower than twice the 5K time, because pace drops as the distance grows.
Key features
- Pace per kilometre and per mile from one finish time.
- Speed in km/h.
- Riegel predictions across common race distances.
- Custom kilometres when your loop is not a standard race.
Common uses
- Turning a 5K time into a min/km training pace.
- A first marathon prediction from a recent half.
- Comparing a watch's pace with a known loop time.
Tips for better results
- Predict from a recent all-out effort, not an easy jog.
- Add time for heat, hills and a first attempt at a new distance.
- Pair with heart-rate zone 2 for easy days so you do not race every run.
Mistakes to avoid
- Using a downhill 5K to predict a hilly marathon.
- Jumping distance too fast because the predictor looked kind.
- Ignoring injury pain because the pace "should" be easy.
Frequently asked questions
Most plans keep the bulk of weekly running at an easy, conversational pace well slower than race pace, with one or two harder sessions such as tempo runs or intervals. Use the calculated race pace for those quality sessions, not every run, and adjust it as your recent race times change.
It depends on the runner. This tool converts your own time; it does not grade you against an age group.
Fatigue is not linear. Riegel's 1.06 exponent is a simple way to model that.
T2 = T1 times (D2 / D1) to the power 1.06. It is a widely used amateur predictor, not a physiological test.
Multiply the per-kilometre pace by 1.609: 5:00 per km is about 8:03 per mile. The calculator shows both so you can follow a plan written in either unit.
Usually 60-90 seconds per kilometre slower than your 5K race pace - slow enough to hold a conversation. Easy runs build endurance; running them too fast leaves you tired for the sessions that matter.
Aim for even splits based on a recent half-marathon time, and resist starting faster than goal pace in the first 10 km. Hills, heat and wind can each add minutes, so adjust the target on the day.