About Run Pace IQ

How the numbers are calculated

Every calculator on the site uses the same two formulas. Distances are handled in kilometres and times in seconds, then converted for display in km or miles.

• time = distance × pace: a 42.195 km marathon at 5:41/km takes about 4:00:00.
• pace = time / distance: a 50:00 10K works out to 5:00/km.

Splits assume even pacing: each split is the pace multiplied by the distance covered so far.

Race time predictions: the Riegel formula

Equivalent race times come from the Riegel formula, published by Peter Riegel in 1977: T2 = T1 × (D2 / D1)^1.06. T1 is a time you ran over distance D1, and T2 is the predicted time for distance D2. The 1.06 exponent reflects how pace slows as races get longer.

Predictions are most reliable between similar distances and assume you have trained for the longer race. Treat them as a starting point, not a guarantee.

Contact

Found a bug or have a question? Email info@runpaceiq.com.