Tools & Calculators
Run in your browser — your runs never leave your device.
Small, focused tools for running with power.
Athlete Settings
Nothing saved yet. Fill these in and the tools below will use them.
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CP calculators
Your critical power and W′, fitted from maximal efforts you have already run.
Critical Power Calculator
Fit CP and W′ from two running-power efforts — typed in, or read from your CP test .fit — and see the power-duration curve.
Multi-Activity CP Calculator
Fit CP and W′ across three or more maximal efforts from separate runs, with a standard error on CP and all three models compared.
Race planning
The numbers a race plan is built from. Each returns one value to carry forward; none of them predicts a finishing time.
Running Effectiveness Calculator
Compute RE — speed per mass-specific power — from a brushed range of a .fit file or manual numbers.
Riegel Exponent Lookup
Look up a fatigue-resistance exponent from a recent race and the distance you are targeting, with the likely alternatives around it.
Environment Adjustment Calculator
Convert a power measured in one set of conditions to what it would have been in another — altitude, temperature and humidity.
.fit tools
Every one of these needs a .fit file. The first reads one; the other three change one and hand it back to download.
Workout Viewer
Drop a .fit file to trace power, heart rate, cadence, pace, and elevation over time.
Activity Trimmer
Forgot to press stop? Keep the stretch you actually ran and drop the rest.
Power Scaler
Recorded at the wrong Stryd weight? Rescale every watt by one constant and download the corrected file.
Distance Scaler
A marathon that read 42.10 km? Rescale the distance by a factor, or land it on the course length.