New take on the classic “Power Zone Calculator”

Everyone has seen the pretty images of power zones; you may have even created one as they are based on simple percentages.

A “zone” simply means a band of power corresponding to a certain intensity. It is simply a short-hand for converting the continuous power-duration curve into several categories.


Zones are arbitrary in the sense, your body does not have any special affiliation with 55% or 75% or 90% of FTP. So whilst any zone does not correspond to any physiological variable it can be useful in training to aim for a certain power band (eg tempo) when training.



However there is something missing from zones, which is built in to the power curve…..time. Let’s say your coach says, ride in zone 5 (VO2max) for as long as possible. How long is that? This would be the point on the power curve where typical zone 5 (lets say middle of it but it could be the bottom figure or the top!) can no longer be maintained. This is known as time-to-exhaustion (in z5).

I wanted to create this for a while, and fortunately time-to-exhaustion (TTE) can be reverse calculated from the power-duration curve. So in this new take on the classic power zone model, we present each zone, linked with TTE.

In addition, one more little trick, you don’t need to know your FTP, you can enter * ANY* best effort. Try it here:


One question, can all the zones be lined up like running pace / swimming pace / lactate threshold. Actually, I found a nice chart rom, so I’ll present that here for now:


I hope this helps! Please pass on the link as or access it here:

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