Running Training Load Race Prediction Calculator

1. Choose a representative performance
   Use a recent race or hard time trial completed under reasonably comparable conditions.

2. Enter known distance and time
   Keep distance units consistent; this page uses kilometers and total minutes.

3. Enter the target distance
   Use the exact distance for the event you want to estimate.

4. Adjust the exponent if desired
   The default 1.06 is a general endurance assumption. A larger exponent predicts more slowing over longer distances.

5. Review time and pace
   Use the forecast as a planning range anchor rather than an exact promise.

Where:

• Known time — total minutes for the known performance.
• Known distance — distance of the known performance in kilometers.
• Target distance — distance to predict, also in kilometers.
• Exponent — power-law endurance parameter; this calculator defaults to 1.06 but lets you change it.

Assumptions: The model assumes the known result represents current fitness and that performance scales smoothly with distance. It does not explicitly model terrain, temperature, altitude, wind, pacing errors, fueling, or event-specific training.

What the result means

The prediction is the time implied by scaling the known performance to the target distance with the selected endurance exponent.

Predictions become less reliable when known and target distances are very different or conditions are not comparable.

Given:

• Known distance: 10 km
• Known time: 50.00 min
• Target distance: 21.0975 km
• Exponent: 1.06

Calculation:
Distance ratio = 21.0975 ÷ 10 = 2.10975. Time factor = 2.10975^1.06 ≈ 2.2064. Predicted time ≈ 50 × 2.2064 = 110.32 minutes.

Result:
About 1:50:19 for the half marathon.

Interpretation:
The model projects a pace of roughly 5.23 min/km, assuming the entered 10K accurately represents current endurance.