Zones benchmarking or calculation by Zwift

I dont know if this shows up after the FTP test or Zwift calculates based on the heart rate, but before starting a ride or after one, Zwift shows a colored chart with my power zones in one side and the heart zones on another.
Are these Zones calculated based on my max heart rate and then by aplying the respective %of max heart rate to identify the zones?
i see some people sugesting to identify zour Zone 2 for example, heart rate and then in a free ride, see how much power you will need to reach that heart rate, being your Zone 2 power. is this necessary, or Ziwft make this for us?
thanks, just want to understand how the zones are created.

The colored zones on the graph are based on a percentage of your FTP, not heart rate. If you want to do zone 2 HR training you’ll have to calculate that for yourself and watch the numbers on the screen. Or use some other device like a Garmin head unit or watch to do it for you.

Which to follow up from what Paul is saying; your HR zones also require knowledge of your MaxHR and accuracy of maxHR, which… is generally speaking not as common as one might think or know.

I can only assume what my MaxHR is based on only two races I’ve done on Zwift over 2.5 years of riding… which to put that into perspective, that’s only a sample of 2 rides out of over 900; on which I’m assuming what is actually my MaxHR. (That’s 0.2% of all rides that I’ve hit what I can only assume is my MaxHR for the record).

That said; if aiming for Z2, but feeling a bit on or off one day, make sure to use the bias feature in workout mode to adjust for your HR.

It’s a perfect use for that feature.

Just be mindful; your HR at the start of the ride, and end of the ride, despite equal power output, will not match; which is what makes HR based training a little wonky, and imperfect.

It’s easy to have steady power output; it’s not at all easy to have a steady HR.

1 Like

The most commonly used HR zones are somewhat arbitrarily defined as 10 percentage point brackets calculated from max HR. Sure, it still works fairly well, but if you know your power zones, you could get much better estimates by doing constant-power efforts (say at least 5 mins each or whatever is long enough for the HR to stabilize) at each power zone boundary (or the most relevant ones ie Z1/2 and Z2/3) instead.

TL;DR if you ride for long enough at a steady power level (depending on your body and fitness and cooling) eventually your heart rate will go up. Doing zone 2 HR training means reducing power as you go.


Ok, if its based on a % of the FTP its fine. i just wanted to understand if Zwift does this calculation or it is just a general chart.
BASed on this i would assime then when my FTP changes automatically, zwift will aslo adjust the zones accordingly right?
thanks for helping

Yes, you are right.

Just be mindful that Zwift itself doesn’t lower your FTP, it will only go up under normal circumstances.
(until they integrate zFTP which is part of their category enforcement system).

So in a case where you get sick and or injured, or are returning after a long period, you either have to lower your FTP, or, (and I’ll need confirmation on this) I think doing an FTP test (any of them), should in theory re-set your FTP in Zwift itself.
(I’ve only done FTP tests a couple of times, so I’m unsure if doing one which ends up lower, will reset a former test)

(just again note this isn’t the same as the category enforcement zFTP; that is determined by your best 90 day efforts from races, rides, etc.)

thanks Andrew,
yes, i understand the category enforcement calculation. that calculation put me in a Cat C, which i still believe is little high…but anyways…it will at least push me…
with the FTP tests you]ve mentioned it will be interesting to know they really adjust automatically.
i remember being in a race and out of a suddenl i got a message that my FTP went up. i guess you dont really need to run a FTP test, Zwift is collecting the data and updating the FTP regularly? not sure.

Yes, youre right.

My understanding is that Zwift estimates FTP from 20 minute efforts, but a 20 minute effort is not everything that goes into an FTP test (it also includes a 5 minute segment at 125% of FTP). This means the estimated result may be high.

You might consider uploading your rides to (it can be linked to Strava). I would trust their estimates more.

If you do want to follow HR zones, use your actual max HR.
If that is unknown, you can start with 220-age the substitute your real max once you determine what it is.
For your 50, 60,70,80,&90%, remember to subtract your rest HR before calculating the % then add it back.

The formula for 80% hr looks like this:
(Max hr - resting hr) x .80 + resting hr

You have to subtract resting hr first because resting hr is a fix value for a person at a certain period of time.
You can’t be at 80 % of your resting hr.
Resting hr does change over time so should be monitored from time to time and can be used as an indicator of rest or illness.

1 Like

yes, i did and they are pretty close, only 4W difference and in the w/kg is basically the same as in Zwiftpower.