Enter a distance and time to get your pace per mile and per kilometre, your speed, and predicted finish times for common race distances.
Predicted finish times at this effort (Riegel formula):
| Race | Finish time | Pace / mi |
|---|
Race predictions use Riegel's formula and assume similar conditions and appropriate training for the distance. Real results depend on terrain, weather, fueling, and your endurance base, and predictions get less reliable the further they are from your input distance. This tool is for educational purposes only and is not medical advice.
Pace is simply your time divided by the distance, expressed as minutes per mile or per kilometre — so a 50-minute 10K is a 5:00 per km pace, or about 8:03 per mile. Speed is the same information flipped around: distance over time, in miles or kilometres per hour.
Runners usually think in pace because it's what you hold during a race, while speed is handy for treadmills and cycling. The calculator shows both, plus your predicted times at standard race distances.
The finish-time estimates use Riegel's formula, a well-established model that scales a known time to another distance by raising the distance ratio to the power of about 1.06. In plain terms, it assumes you slow down a predictable amount as the distance grows.
It's a solid guide, but it assumes you're trained for the target distance. Predicting a marathon from a 5K will look optimistic unless you've put in the long-run mileage, so trust predictions most when the race distance is close to what you entered.
The most common racing mistake is starting too fast. Going out quicker than your goal pace burns energy you'll badly want in the later miles, and the time you bank early is usually lost — with interest — at the end.
A more reliable strategy is even or slightly negative splits: run the first half at goal pace or a touch slower, then speed up if you feel strong. Use your calculated pace as the target to settle into after the first mile.
Most of your weekly mileage should be easy — comfortably conversational, often a minute or two per mile slower than race pace. Easy running builds the aerobic base that makes race pace sustainable. Tempo runs sit at a "comfortably hard" effort, and intervals are faster than race pace in short repeats.
If every run is at the same moderate pace, progress tends to stall. Varying intensity — mostly easy, with focused hard days — is what drives improvement.
Pace tells you how fast you're going; heart rate tells you how hard your body is working. On hills, in heat, or when tired, the same pace can cost a much higher heart rate, so pairing the two gives a fuller picture of effort.
Many runners use heart-rate zones to keep easy days truly easy and to gauge race effort, which helps avoid the start-too-fast trap.
Divide your time by the distance. For example, 50 minutes for 10K is 5:00 per km, or about 8:03 per mile. Enter your distance and time above and the calculator does both units.
They use Riegel's formula and are most reliable when the predicted distance is close to what you entered and you're trained for it. Long extrapolations, like marathon from a 5K, tend to be optimistic.
It varies widely by age and experience. Many recreational runners finish a 5K around 9 to 12 minutes per mile; what matters more is improving against your own times.
No. Most runs should be easy, with a smaller number of faster tempo or interval sessions. Varying intensity builds fitness better than running every day at one moderate pace.
Running the second half of a race faster than the first. Starting controlled and finishing strong is usually more effective than going out too fast and fading.