WIMSTA

Running Pace Calculator

Give any two of distance, time and pace — this fills in the third and your speed. Then predict a race time at another distance, shown as an honest range.

Pace, time, distance — enter any two
km
min / km
Enter any two of distance, time and pace to solve the third.
Predict a race time

From the run above, estimate a finish at a new distance. We use the Riegel formula across its 1.06–1.08 fatigue range, so the answer is a band — accuracy drops the further the distances are apart.

km

Solve a run above, then enter a target distance.

Pace, time, distance — pick any two

  • Pace = time ÷ distance (min per km or per mile).
  • Time = pace × distance.
  • Distance = time ÷ pace.
  • Speed = distance ÷ time (km/h or mph).

Switch km/mi freely; enter time as h:mm:ss and pace as m:ss.

Predicting a race time — and why it’s a range

To estimate a finish at a new distance we use the Riegel formula: T₂ = T₁ × (D₂/D₁)^1.06. The exponent 1.06 is the classic “fatigue factor”, but real runners fall anywhere between 1.06 and 1.08, so we show the prediction as a band across that range rather than one figure. The wider truth: a prediction is only as good as the effort behind your input run — and accuracy drops the further the two distances are apart. Projecting a marathon from a 5K is optimistic; predicting a 10K from a 5K is far more reliable. Treat it as a target window, not a guarantee.

Source: Riegel PS. “Athletic Records and Human Endurance.” American Scientist 1981;69(3):285–290.

FAQ

How do I calculate my running pace?

Divide your time by your distance. 50 minutes over 10 km is 5:00 per km; the same run in miles is about 8:03 per mile. Enter any two of distance, time and pace above and the calculator does it — and gives your speed too.

What is a good running pace?

There’s no single answer — it depends on distance, fitness and terrain. A common recreational range is roughly 6:00–7:00 per km (about 9:40–11:15 per mile) for easy running, faster over shorter races. Your own trend over time matters more than any benchmark.

Can I predict my marathon time from a 5K?

Roughly, but treat it as a wide window, not a number. The prediction here uses the Riegel formula across a 1.06–1.08 fatigue range, and accuracy falls the further apart the distances are — a marathon is a big extrapolation from a 5K, so expect real conditions and training to move it several minutes.

What’s the difference between pace and speed?

Pace is time per distance (minutes per km/mile) — lower is faster. Speed is distance per time (km/h or mph) — higher is faster. They’re the same information turned inside out; the calculator shows both.

How do I convert min/km to min/mile?

Multiply your min/km pace by about 1.609. 5:00 per km is roughly 8:03 per mile. The calculator switches units for you.