well there is some sort of “official” metrics for each category:
But from my own experience in Zwift the reality is slightly different from those numbers.
When I’ve started with Zwift I could barely hang with the D cat and the real numbers were different.
So, there are some numbers of categories metrics with the FTP, but in reality if you would like to be in the middle of group D you should be able to hold 2.5 w/kg for at least 30 minutes and you should be able to push at least 2.8-3.5 w/kg up the hill. To be in front of group D you should be able to push 2.5w/kg during the whole race. For cat C in order to be in the middle you should hold at least 2.8-3.1 for at least 30 minutes and push 3.5-4 w/kg up the hill. In order to be in top of cat C you should be able to hold the whole race (in some cases 60+ minutes) with non-stop 3.2 w/kg, push at least 4-4.5 up the hill and sprint no less then 6.5-7+ w/kg.
With the reality of today, in order to win cat C race with high level of participation one should be able to ride at the level of cat B at least. Same for the B cat, one should be able to ride at the level of A cat.
By the logic of things it shouldn’t be like this, since if the max FTP for group C is 3.2 w/kg you would not expect riders, even in the top 10 to hold this speed for an hour, but the reality is different. Same for group B.
So, at least for the front riders of each group always expect much higher numbers. There is also another side of the coin when there are more strong riders in lower categories. So you could find A, B, C riders in D cat. Or A and B riders in C category.
You could always subscribe to zwiftpower.com and connect it to your Zwift account. This will allow you to see your race stats in different manner together with own rating and your place vs other riders in the zwiftpower rating system. In some races results zwiftpower will place riders in appropriate categories automatically by using the race data. So, a lot of riders are using this source as their main “real results” race source.
The whole topic about categories and rating is highly discussed in different forum topics and this is definitely something that people care about.
ah…concerning the start of events
races for D cat, the front group will ride probably around 3w/kg for the first one or even two km. The first 500 meters with 3.5-4 w/kg start.
races for C cat, the front group will start the ride with something like 3.5-4+ w/kg for the first km or two. And the first 500 meters with approximately 4.5 or even 5 w/kg
For social events with an advertised average of 2.5w/kg, if this is a big event with a lot of participants, would be a good idea to start the event with 3.5+w/kg for the first 500 meters and then hold around 3+w/kg till the first or second km. Probably during those events the speed up hill will be around 2.7-3w/kg, and around 2.2-2.4 w/kg on flat.