Running Pace Calculator
Calculate your running pace and speed, and predict finish times at standard race distances.
Race Finish Predictions
Riegel's model, which allows for the pace you lose over longer distances. Assumes you have trained for the target distance.
Medical disclaimer. This calculator is for general information and education only. It is not medical advice, not a diagnosis, and not a substitute for professional care. Training paces are general guidance. Build volume gradually, and take advice before starting a new programme if you have a cardiac or respiratory condition.Speak to a doctor or another qualified clinician about any health decision.Last reviewed .
Frequently Asked Questions
How is running pace calculated?
Running pace is calculated by dividing total running time (in minutes and seconds) by total distance (in kilometers or miles).
What are standard race distances?
Standard distances include 5K (5 km), 10K (10 km), Half Marathon (21.0975 km / 13.1 miles), and Full Marathon (42.195 km / 26.2 miles).
What is a good 5K pace for beginners?
A beginner 5K pace is typically around 6:00 to 7:30 min/km (roughly 30 to 37 minutes total time).
Is my running data saved or uploaded?
No. All pace calculations run 100% locally in your web browser.
How does the race time prediction work?
It uses Pete Riegel's 1981 endurance model: T₂ = T₁ × (D₂ ÷ D₁)^1.06. The 1.06 exponent encodes the observation that pace slows slightly as distance grows — doubling the distance takes a little more than double the time. It is most reliable between about 1,500 m and the marathon, and it assumes you have actually trained for the target distance.
Why is my predicted marathon time optimistic?
Because Riegel's model describes the physiology of pacing, not glycogen depletion, heat, or the specific endurance a marathon demands. A runner with a strong 10K but a low weekly mileage will almost always run slower than predicted over 42 km. Many coaches apply an exponent nearer 1.10 for marathon predictions from short-distance results.
What is the difference between pace and speed?
They are reciprocals. Pace is time per unit distance (minutes per kilometre), speed is distance per unit time (kilometres per hour). Runners think in pace because it maps directly onto what a watch shows mid-run; cyclists think in speed. 5:00 per km is exactly 12 km/h.
How do I convert between min/km and min/mile?
Multiply the per-kilometre pace by 1.60934 to get per-mile. A 5:00/km pace is 8:02/mile. The conversion is often done wrong by converting only the minutes — 5:00 becomes 8.05 minutes per mile, which is 8 minutes and 3 seconds, not 8 minutes 5 seconds, because the decimal is a fraction of a minute rather than seconds.
What is negative splitting?
Running the second half of a race faster than the first. It is how most distance records are set, because starting slightly conservatively preserves glycogen and limits early lactate accumulation. The common mistake is the opposite: going out fast while fresh and paying for it disproportionately in the final third.
The formulas behind the numbers
pace = total time ÷ distance speed = distance ÷ total time Riegel: T₂ = T₁ × (D₂ ÷ D₁)^1.06
The exponent is what makes Riegel's model useful. An exponent of exactly 1.0 would mean you could hold the same pace at any distance, which is plainly false. At 1.06, doubling the distance multiplies the time by 2^1.06 ≈ 2.085 — so a 25-minute 5K predicts roughly a 52-minute 10K rather than 50 minutes.
Standard race distances
5K 5.000 km 3.107 miles 10K 10.000 km 6.214 miles Half marathon 21.0975 km 13.109 miles Marathon 42.195 km 26.219 miles
The marathon's awkward 42.195 km dates from the 1908 London Olympics, where the course was extended so it could finish in front of the royal box. The distance was standardised at that figure in 1921 and has stood since.