How this calculator works
Functional threshold power is the highest power you can hold for about an hour. Training zones are shares of that value, so they move automatically when FTP changes. The seven zones follow the widely used Coggan model. Zone 1 is easy spinning below 55 percent. Zone 2 is aerobic endurance from 56 to 75 percent. Zone 3 is tempo at 76 to 90 percent. Zone 4 sits at the threshold itself, from 91 to 105 percent. Zone 5, from 106 to 120 percent, develops VO2 max. Zone 6 covers short anaerobic efforts from 121 to 150 percent, and zone 7 is neuromuscular sprinting above 150 percent. The upper end of zone 7 is open, so the table stops at a practical display ceiling.
Formula
Zone lower watts = FTP x lower share. Zone upper watts = FTP x upper share. Shares are zone 1 up to 55 percent, zone 2 56 to 75 percent, zone 3 76 to 90 percent, zone 4 91 to 105 percent, zone 5 106 to 120 percent, zone 6 121 to 150 percent and zone 7 above 150 percent.
Worked example
An FTP of 250 W puts zone 2 at 0.56 x 250 = 140 W to 0.75 x 250 = 187.5 W, usually shown as 140 to 188 W. Zone 4 runs from 227.5 to 262.5 W. Zone 6 runs from 302.5 to 375 W. A rider who can hold 250 W for an hour can therefore do endurance rides around 140 to 188 W and threshold intervals near 228 to 263 W.
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Frequently asked questions
How do I find my FTP?
A common field test is a 20 minute all-out effort, with FTP estimated as 95 percent of the average power. A ramp test or a longer threshold test can also be used. Whichever test you choose, repeat it the same way so the zones stay comparable.
Why are there seven zones and not five?
Different coaching systems use different counts. The seven-zone model separates anaerobic capacity from neuromuscular sprinting, which matters for track and criterium training. A five-zone model simply groups some of these ranges together.
Should outdoor rides use the same zones?
The watt ranges are the same, but wind, hills and drafting change the power needed for a given speed. Use the zones for the effort and let speed follow the terrain rather than chasing a watt number on a descent.
How often should I retest FTP?
Every six to eight weeks during a build, or after a long break. Fitness gains of a few percent are normal, and zones that are ten percent out of date can make easy rides too hard and hard rides too easy.