Race Time Predictor
Enter a known distance and time plus a target distance, and this tool applies the Riegel formula (target time = known time times (target/known)^1.06) to predict your race time. For 5 km in 25 minutes, a 10 km target predicts 52 min 7 s.
What this calculator does
The Race Time Predictor estimates your result instantly from the values you enter, using standard health & fitness formulas. Enter a known distance and time plus a target distance, and this tool applies the Riegel formula (target time = known time times (target/known)^1.06) to predict your race time. For 5 km in 25 minutes, a 10 km target predicts 52 min 7 s. Calculations run in your browser, so nothing you type is sent to a server, and the output is an estimate rather than a certified or official figure.
Result
About Race Time Predictor
The Race Time Predictor uses the Riegel formula to scale a known performance to a new distance. Enter a distance you have run and its time, plus the target distance, and it estimates the time using the exponent 1.06.
Formula & Mathematical Calculation
Predicted Time (minutes) = f(Known Distance (km), Known Time (minutes), Target Distance (km))
Calculated according to standard health formulas implemented in the calculator core.
Calculation Example
Enter a Known Distance of 5 km, a Known Time of 25 minutes, and a Target Distance of 10 km. The calculator computes 25 x (10/5)^1.06 and shows a Predicted Time of 52 min 7 s, noting the Riegel formula predicts about 52.1 minutes for 10 km.
Key Benefits
- Applies the recognized Riegel endurance formula with a 1.06 exponent
- Predicts time for any target distance from one known result
- Shows the prediction in minutes and seconds
- Reports the predicted total in minutes in the interpretation line
How to Use this Calculator
-
Enter your known result
Fill in Known Distance (km) and Known Time (minutes) from a race or run you have completed. -
Enter the target distance
Type the Target Distance (km) you want a prediction for. -
Calculate and read
Click Calculate and read the Predicted Time box in minutes and seconds.
Assumptions & Limitations
What the calculation assumes
- Every value you enter is treated as an exact, known amount.
- Any rate or interval you enter is assumed to hold for the whole period unless the form asks for it separately.
- Results use standard published formulas and account only for the values entered above.
- Rounding is applied for display; the underlying calculation uses your full precision.
- Results are returned in the same units you enter, unless the tool states the output unit.
What it does not cover
- Race Time Predictor produces a calculated result for reference and learning, not a certified or official measurement.
- Real-world outcomes differ when tolerances, rounding rules or local standards apply.
- Definitions and standards vary by region and change over time; verify the convention that applies to your case.
- Figures are only as accurate as the inputs you supply — check them before acting on the result.
- For work where the result carries real consequences, confirm it against an authoritative source.
Frequently Asked Questions
Free to use, no account needed. Calculations run in your browser, so nothing you type is sent to a server. Results are estimates — how we build and check our calculators.