Free · Running calculators 🏃

Running Race-Time Estimate with a 1.06 Exponent

Project a race time from a known distance and finish time using the explicit distance-ratio power model, with selectable distance and duration units.

Formula & worked example
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Calculator inputs

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How to use this calculator

Enter the known values in the units shown. Results update as you type.
Where results are editable, change one to solve backwards. Lock a value to hold it fixed.
Use the worked example to check the method. Reset restores the starting fields.

Private by default

Inputs and results stay in this browser tab. Bookify does not upload or store the values you enter.

Formula and method

At the same distance, the model returns the entered time. Doubling the distance multiplies time by 2^1.06, approximately 2.085.

Estimated time₂ = known time₁ × (distance₂ / distance₁)^1.06

Worked example

Enter these known values and leave the other values blank.

Run distance: 5 km
Run time: 20 hrs / min / sec
New run distance: 5 km

Predicted time: 0:0:20 hrs / min / sec

Assumptions and limitations

Distances and elapsed times must be positive. The two distance units are normalized before forming their ratio.
The exponent is fixed at 1.06. This is a power-law estimate commonly used in race calculators, not an individualized fitness model.
The estimate assumes comparable effort, preparation and conditions. It does not account for elevation, weather, terrain or injury.
A short-distance result can be an optimistic predictor for a much longer race without suitable endurance training. Treat the output as a model estimate, not a guaranteed finish time.

Common questions

Does this tool solve backwards from the predicted time?

The captured model computes the new time from a known race and target distance. Enter the other race as the known result to reverse the scenario.

References

The calculation equations, inverse formulas, units, and input rules were imported from this source. Bookify provides the interface and equation solver.

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