I know the default Zwift trainer difficulty setting is 50%, and there is a minimum and maximum setting which would be 0 and 100% respectively.
I think it would be helpful if there was a readout that lets you know what % you are at if you move the slider. I read where people say they like 40% but they are just eye-balling what they think is ~40%.
Would it be possible to give us an actual value for the slider setting?
Thank you.
Think of it in terms of variability the slider only dictates how much full scale resistance your trainer utilizes.
Let me use the kickr as a the example. (For a 75kg rider the sim mode provides at full scale 15% grade resistance)
At 100% if you are a 75kg rider you will feel a full 15% grade at or above 15% beyond that it can not do more
On the other end if you are going down hill at a -15% grade there is like no resistance at 100% (this being said the tacx neo has a motor inside to propel you down a simulated 5%)
At 50% the max grade felt is 7.5% at 15 and above
At 50% the max downward resistance is not full release
I know what you mean, even if the above poster doesn’t 
You can set a definitive value if you go into
Documents/Zwift/prefs.xml
In there you’ll find a line which looks like this
<TRAINER_EFFECT>0.5</TRAINER_EFFECT>
You can alter the value between the tags to be whatever you want. It’s a multiplication factor not a percentage however. So 0 is 0%, 0.5 is 50% and 1 is 100%.
Hope that helps.
Thank you Mark, yes sir that does help.
Sorry it’s been a while since I responded. What I did in the mean time was I made my own ruler. I used a piece of paper and measured the scale 0-100 on my T.V. screen. Then I marked on the piece of paper what 25%, 50%, and 75% would be and then held the paper up over my T.V. screen. The default setting is 50% and it hit my paper measurement smack dab in the middle. 
The prefs.xml tip is great, but Zwift should still put number to the slider.
C’mon Zwift, give us a numerical readout. I shouldn’t have to edit the prefs to get a precise figure.
I agree, it’s silly that there isn’t a numerical value for this provided on the settings screen. Personally I like to set the difficulty to make the in-game gradient feel as realistic as possible. This requires some experimentation and moderate precision. Also sometimes I might change the setting and then want to put it back to exactly where it was before. A non-marked slider is an inappropriate interface for this variable - why not just have a number and + & - buttons?