Hey, i have one question is there any chart or something to show you what watts should you pedal at specific gear.
example 52/23 80rpm = 220watts
i would like to know this because i have a feeling that my watts are to low.
I am riding 52/36 12/27
On elite qubo powermag setting 3 and garmin gsc 10 speed/cadence sensor. And i cant ride 20 min on 220watts on wattopia which is absurd, because i had ftp 275 on trainerroad. Any help?
Too many factors go into a system like ZPower to have a simple chart back to cadence.
You might be able to get an idea of Wheel Speed to ZPower but that is still probably ±20%.
Best bet is borrow a powermeter if you can and ride for 10 minutes then calibrate and record the powermeter with one device and ZPower in zwift and analyze the data side by side afterwards. Even then don’t expect to get closer than about ±5%.
AKA accuracy is difficult!
I think the goal should be repeatability over accuracy. Because the algorythm used in Trainer Road, Zwift, etc. are different, it is not surprising the results are different. I suspect your power on the road will be different yet again.
I would suggest that you adopt the power defined by each app. In effect, your will have a FTP 275 in TR, maybe 260 in Zwift and 240 in the real world. (I am just tossing in numbers here). If you know these values, train to these values in the world you will ride in.
The effort you exert will be the similar for each app at the apps respective FTP test result. If your FTP in TR is 275 and Zwift results in 250, the effort should be the same. Train to those numbers in the respective app.
Sounds complicated, but is easy to adapt to.
Thanks for replys. Yes i agree u cant compare both apps. As Bruce law said, if my zwift ftp is 240 i dont care, just train to this numbers and dont mind on numbers in trainerroad. But is hard to watch ,when i am dying on my bike with 240w and get overtaken by riders with 3,5/4w per kg. 
sry about my english 
How much do you weigh? Your weight is a critical factor.
Two riders produce 300W each, one weighs 86kg, the other weighs 75 kg. Their respective w/kg will be 3.5 w/kg and 4.0 w/kg.
If a third rider is producing 300 and weigh 100 kg, their w/kg is 3.0 (300w/100kg=3.75), they will get over-taken by the riders producing 3,5/4 w/kg .
If this scenario doesn’t fit your situation, that is your w/kg is 4 or so at 300w, then do the Zwift 20 minute FTP test and use that FTP result.
I have set zwift to 85kg. I might have 80kg now, i didnt weight myself for a months kol
At your 2.8 w/kg (240/85), those riding at 3.5 - 4 w/kg will be considerably faster than you.
For you to go the same speed as those producing 3.5 - 4 w/kg, you will need to put out 297 - 340W.
Another aspect you may want to address is cadence. You will need to exert considerably more pedal force at 240W with a cadence of, say 65, than you would at a cadence of 95 RPM. This will not alter your w/kg, but will make pedalling easier.