Big difference between Ramp Test FTP and Xert calculated FTP

Hey, I’ve been using xert for a while now have around 3 weeks of data with a power meter uploaded to it mostly outdoor rides and more recently a couple indoor rides. Problem is xert FTP calculations give me an FTP of 280 watts however I did a indoor ramp test yesterday (which is also uploaded into xert) which gave me an FTP of 235.

My peak power seems to be close to what it is, just my FTP from xert differs a lot from my indoor ramp test. Do I have any outdoor activities that are screwing up my calculation somehow? Is the indoor factor that makes my FTP be lower from what xert calculated using outdoor rides as well?

Would like some clarification if possible since from 235 to 280 it’s still quite a big jump and not sure on what I should base my training :stuck_out_tongue: .

Ah I use exactly the same powermeter indoors and outdoors so there is no variation there!

There can be differences between a RAMP test and your Xert fitness signature as Xert calculates the numbers based upon watts achieved while fatigued and the relationship between PP, HIE and TP.
For best results try a multi-dimensional test by searching the workout library for “breakthrough” and perform one of the BT workouts in slope mode on your trainer.
When you hit the section where MPA is purposely drawn down and you are about to tap out, spin up out of the saddle and try to sprint as hard and long as you can. 5-7 seconds minimum or longer is possible.

If you are new to Xert there are lots of tips in this thread –
Beginner questions - Support - Xert Community Forum (

You can also ask Xert support to take a look at your data and adjust signature if required (

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How long ago was your breakthrough in Xert? Also an FTP calculated from a ramp test is very personal and can range from 72% to 77% of your peak 1 minute power on the test. It is also very dependant on the test protocol. The problem is nobody has any idea where on that range they are. One final thing: Xert’s TP is NOT FTP, it’s the power when your MPA starts to decline and only correlates approximately with FTP.


FTP is both the best and worst concept ever developed. it is good because it provides so idea of capacity, on the other hand the way to get the “number” is just that a number and not a fact. Each method is going to provide a slightly different in some case and a large difference in other cases depending upon a long list of potential confounds. So comparing TP to FTP is like apples and oranges they are both somewhat round fruit after that they are completely different.

So don’t get so hung up on comparison between systems or test s etc. Find a system or test that works for you and stick to it but IMHO people need to stop trying to compare the results of different system and trying to believe they should be the same. Each has it use and in the right hands can be a very good tool. The Xert approach has it strengths and weaknesses like all systems but if you stick with it you will probably find that the outcome is pretty solid and that is the proof, the outcome which is not a bigger number but when you ride your bike your fitness has improved and that is the real measurable that one needs to deal with. There are the workouts in Xert that will help dial in your signature, they are sort of like tests but they are meant to stress you to the point of failure in a more real world manner. When was the last time you did a ramp test outdoors on the road… but you can produce a breakthrough in the real world, not just the lab/ trainer/workout with a special protocol. So pick a system you feel comfortable with and stick to it. The comparison between systems is just going down a rabbit hole or through the looking glass, and probably will not get you much satisfaction in the end.


Keep in mind that Xert’s definition of Threshold Power is different than most other platforms. Rather than giving a value that you can hold for XYZ minutes, Xert’s Threshold Power displays the power at which fatigue increases faster than it dissipates (e.g. where MPA begins to decline). In my mind, that’s a more important (useful?) training metric than the power that you can hold for 60 min, in addition to the finer details about fatigue above threshold by tracking HIE & PP in addition to TP.


Thank you so much for the replies, learned a bit about it but it really seems Xert miscalculated what I can do. Not sure how much is due to indoor vs outdoor power but I simply cannot complete Xert workouts like you sugested based on the numbers xert calculated for me. So what I did was flag all my outdoor activities for now and just keep the indoor ones. That brought my calculated TP down to 238w (was around 280w) and my fitness planner updated to show that I’m tired atm which I think it is a more accurate description to how I feel atm :smiley: (was very fresh before i flagged the outdoor activities)

Going to rest and try my hand at the workouts again once I recover now with the updated numbers.

Again thank you so much for the help, going forward will keep track of outdoor activities and flag if I see a big increase in numbers randomly.

My last breakthrough was from an outdoor activity around 2 days before my ramp test in xert :stuck_out_tongue: