Cycling power and FTP — what the watts in your .fit file mean
Cycling power is the one number in endurance sport that is genuinely measured, and almost every other cycling metric is quietly built on top of it.
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a .fit file from a watch or bike computer
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Power is measured; the rest is arithmetic on it
A power meter measures force at the pedals or hub and reports watts directly — unlike running power, which is estimated. That raw watt stream is the foundation, and the familiar training numbers are transformations of it: average power is its mean, normalized power weights the hard efforts more heavily, intensity factor scales it against your threshold, and training stress combines intensity and duration. All of them come out of the same per-second power field your file already holds.
FTP is a reference point, not a field
Functional threshold power — roughly the power you can hold for an hour — is not stored in the file; it is a value you set, and every intensity and stress figure is computed relative to it. Change your FTP and the same ride’s intensity and stress scores change, though not a single watt did. That is why two apps can disagree on how hard a ride was while agreeing exactly on the power: they are using different FTPs against identical measurements.
Read your raw power here
This page reads the power field from your .fit file on your device and shows the actual watt stream — the measurement everything else is derived from — rather than a single summary number. It runs locally and uploads nothing, so you can see the raw data your training metrics were computed on.
This is one field among many. Open your .fit file to see every field it holds, or the activity-type list for what each sport records.