Calculate FTP and cycling power zones
Functional Threshold Power (FTP) is a practical cycling-performance metric used to organise power-based training. ATHLOMETRY lets you enter a known FTP or estimate one from the mean power of a 20-minute time trial.
FTPPower reference in watts
W/kgRelative power when body mass is entered
7 zonesAutomatic power ranges
20-minute FTP estimate
Estimated FTP = 20-minute mean power × 0.95
The 95% correction is a widely used field-testing convention. Research shows the 20-minute protocol can be reliable, but the relationship between 95% of 20-minute power and other physiological thresholds varies between individuals. Treat the result as an FTP estimate rather than a direct measurement of lactate threshold or critical power.
Why calculate W/kg?
Absolute watts describe the power produced at the pedals. Dividing FTP by body mass adds useful context when body mass influences performance, especially during climbing. W/kg does not replace absolute power: both matter depending on the cycling task.
How to use FTP zones
The seven-zone table converts FTP into practical power ranges. These zones are useful for planning and communication, but they are model-based ranges rather than directly measured physiological boundaries.
Why multiply 20-minute power by 95%?
The correction attempts to estimate a more sustainable power from a shorter maximal effort. It is a practical convention, not a universal physiological constant.
Is FTP the same as lactate threshold?
No. They can be related, but research shows they should not automatically be treated as interchangeable measurements for an individual cyclist.
Do I need body mass?
No. Body mass is only required to calculate W/kg. FTP and power zones can be calculated from watts alone.
How often should I retest FTP?
Retest when you need an updated training reference, ideally after a meaningful training block and under similar testing conditions rather than simply testing as often as possible.