Open a treadmill-run .fit file — distance without GPS
Indoors there is no GPS, so a treadmill .fit file’s distance is an estimate — and knowing what it is estimated from tells you why it disagrees with the machine.
Open your file
Drop your file here
a .fit file from a watch or bike computer
No account. No upload. The file is read on this device and never leaves it.
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Where the distance comes from
A treadmill run’s distance is not read from the treadmill. Unless you have a connected foot pod, the watch estimates it from wrist swing and your stride model, which is accurate for steady running and drifts on intervals, hills-mode, or a change of pace the model has not learned. So the file’s distance and the belt’s readout are two independent guesses, and a gap between them is expected rather than a fault.
Calibration is a factor stored per activity
Many watches let you correct an indoor run afterwards against the treadmill’s number, and that correction is applied as a scale factor. A file recorded before calibration and the same file after can carry different distances for identical motion. Reading the raw record lets you see the pre-correction estimate, which is the honest measurement the stride model produced.
What you get from this page
This page opens the file on your device and shows the sport as treadmill, the absence of any position fields, and the distance and cadence the watch derived — so it is clear the number is a motion estimate, not a measured track.
In the corpus this tool is tested against, 69 activities resolved to this sport. See the full activity-type list for every sport a .fit file can declare, and open any .fit file whatever its sport.