What this calculator does
Race time predictor works out predicts a finish time at a new distance from a recent race result, using Riegel’s formula. Enter your own figures above and the answer updates as you type: nothing is fixed in the code, so the result reflects exactly the numbers you supply.
The formula this calculator evaluates is printed under the tool and explained below, so you can check the working by hand or reuse it in a spreadsheet.
The formula
FormulaT₂ = T₁ × (D₂/D₁)^1.06
The inputs explained
| Field | What to enter |
|---|---|
| Known distance (km) | A number, measured in km. Starts at 10. |
| Known time (min) | A number, measured in min. Starts at 50. |
| Target distance (km) | A number, measured in km. Starts at 21.1. |
Worked examples
Every figure in the tables below is produced by this page’s own calculator at build time, so the numbers and the tool always agree. Select any row to load that scenario.
How the answer changes with known distance
Every other input is held at the calculator’s starting values while known distance varies. Select any row to load that scenario into the calculator.