Zwift vs Zwiftpower Category Placement

The Zwift calculations for category placement are different than what Zwiftpower uses.

Is there a place in which Zwift shows you your category and the numbers used to determine Zwift category?

nope. but these are the vaguely defined limits Category Enforcement FAQ the exact calculation is different though

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I have been in C grade since first upgraded from my first race in D grade on Zwift. I have usually been top half of the field. In ZRL finishing between 10th and 35th depending on terrain, but usually keeping up with the main bunch. Now I am auto-categorised to B, but my wkg is only 3.17 and using your formula for MAP, I am 3.67, well below the 4.1 cut off for B grade. Is there a caluclation bug in the system. My C grade team mates who finish either side of me haven’t been upgraded.

Keep in mind that the data used to calculate your minimum category under CE is not necessarily visible to you. It’s not based on the data in ZwiftPower - it’s everything you did in game in the last 60 days. If you track all of your Zwift rides in some other application (eg, Strava, TrainingPeaks) you may want to review that data to see if you’ve exceeded the numbers you can see in ZwiftPower. You may also be able to find a super performance in your Zwift ride history, though that can be a lot of effort to review. For example if you did a free ride with a poorly calibrated power meter that overestimated your power, that would count toward your CE minimum category.

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Please be aware it is also not just about what you do at exactly the 20 minute mark it is also about what average power you put out at other various points of time. My own current best (60 and 90 day) for 20 min is 3.12 wkg because I am not at the moment making any 20 minute serious efforts. These lack of efforts moved me from an acceptable lower/mid B category rider to CE cat C. I then undertook a Herd Series climb race where I put in new personal power bests for 3.5 to 7.5 minutes. This effort immediately moved me from CE category C straight back to B category, exactly as I believe the system is expected to do, even though throughout the whole ride I only achieved 20 minute best of 2.8wkg.

I’m not sure anyone, outside of Zwift HQ staff, on this forum can tell you exactly what the CP and MAP/VO2 max calculations are. I can try and offer you three possible answers to your question - I’m not going to say any of these are correct but possibly enough to reassure you there is probably not a bug in the system in your situation.

  1. If you accept you have a 20 min best of 3.17 then IF Zwift are rounding to nearest 1decimal point then that is actually 3.2 and CE is >=3.2 for cat B

  2. During your ride on 28th June you put out some serious long duration efforts climbing Leith Hill. In fact at the very top just as you started to coast downhill you had put in a 19 minute effort of 3.22wkg. IF that 19 minute effort is used by Zwift to set your CP curve there is a good chance your CP might end up as 3.2 or just higher.

  3. I quite like this article on Critical Power.

I’m not saying that Zwift are using any of the Critical Power calculations within the article but I like to use the two test method CP calculation.

In your own situation from your power curve you have:
3 minute max power of 320
12 minute max power of 291 (going up Leith Hill)
Your CP = ((12 x 291)-(3 x 320)) / 9 = 281.33 watts

Divide this by your weight (87.1kg) gives a CP of 3.23wkg

Zwift may not be doing any of these things but I hope you can see that you are right on or above the Category Enforcement B category limit.

You are of course still a ZwiftPower category C rider and can race in that category in ZP operated races.


Thanks Ian for such a detailed response! Looking back at the DIRT race with the Leith Hill, climb, I did have good legs and did a PB that nearly killed me. I suspect you have nailed it with that CP calc from 3 to 12 minutes. I had presumed from the article above (Milan post) that used a CP of 4.1 wkg to move into B grade.

Seems I’ll be quite rightly out the back of B for the next 2 months!