FTP (Functional Threshold Power)

FTP, or Functional Threshold Power, is the highest average power output, measured in watts, that a cyclist can sustain for approximately one hour without significant fatigue. It represents a rider's physiological ceiling for sustained effort and serves as the central benchmark around which structured cycling training plans are built, since it reflects both aerobic capacity and lactate threshold in a single, measurable number.

Because a true one-hour maximal effort is exhausting and difficult to pace accurately, most cyclists estimate FTP using a shorter, more manageable test — typically a 20-minute maximal effort with the resulting average power multiplied by 0.95 to account for the slightly higher intensity a rider can sustain over 20 minutes compared to a full hour. The Cycling FTP Calculator automates this estimation, taking 20-minute test power as input and returning the estimated FTP along with associated training zones.

FTP is closely related to VO2 Max, the maximum rate at which the body can utilize oxygen during intense exertion. While VO2 max sets an upper physiological ceiling for aerobic performance, FTP reflects how much of that capacity a rider can actually sustain over a meaningful duration, incorporating lactate threshold and pacing efficiency. Two riders with similar VO2 max values can have noticeably different FTPs depending on how well-trained their lactate threshold and muscular endurance are.

FTP (watts) = 20-Minute Average Power × 0.95

Where 20-Minute Average Power is the rider's average power output, in watts, sustained during a maximal 20-minute effort, and 0.95 is the standard correction factor scaling that shorter effort down to an estimated one-hour sustainable power.

A cyclist completes a 20-minute maximal test with an average power output of 300 watts.

FTP = 300 × 0.95 = 285 watts

This 285-watt FTP estimate would then be used to calculate training zones — for example, an endurance zone around 160 to 214 watts (56–75% of FTP) and a threshold zone around 259 to 299 watts (91–105% of FTP) — giving the rider clear power targets for different types of workouts.

• FTP is estimated, not measured directly, in most training programs: the 20-minute test with a 0.95 correction factor is the standard practical substitute for a genuine one-hour maximal effort.
• Training zones are calculated as percentages of FTP: structured cycling plans divide effort into zones like endurance, tempo, and threshold, each defined as a percentage range of the rider's current FTP.
• FTP should be retested periodically as fitness changes: most cyclists retest every 4 to 8 weeks so their training zones stay aligned with their current fitness level.
• FTP depends on more than just aerobic capacity: while a high VO2 max supports a high FTP, factors like lactate threshold, pacing skill, and muscular endurance also strongly influence the final number.
• Higher FTP relative to body weight indicates stronger climbing performance: cyclists often track FTP per kilogram of body weight (watts/kg) as a normalized measure of climbing and racing ability.