Garmin Estimates FTP?

After my last A race about a month ago I was happy to see that my Garmin “spit out” a new FTP estimate based on the ride. It was about 11w higher than my previous (recorded) best so of course I changed my FTP on TR!

The race was a back country MTB course with some sustained climbs, however I don’t think any of the sustained climbs were over 10 minutes. Does anyone know what Garmin uses to calculate an FTP like this? I haven’t been doing a ton of structured workouts but the ones I have seem to be ok based on the new FTP. I feel like that FTP is pretty close and I’ll be checking it with an assessment next week.

Any insights?

Garmin bases it’s FTP on 8 minute efforts.

For me and a lot of other people it’s been real close or exactly to what I’ve ramped the last time I did. So according to my unscientifical opinion it’s pretty accurate. Like 1-3W accurate.


This is quite interesting. Garmin Edge 530 has my FTP 189, power meter source are Assioma Duo pedals. On Trainer Road my Ramp test has me at 171. I adjusted my Garmin to FTP 171. Now I’m second guessing myself. I have never failed to finish any of my workouts always hit the target power. The workout are always hard and on some I have almost bailed, but I tell myself I’m not a quitter. The smart trainer is a Wahoo Kickr 2017, always make sure to calibrate it. It’s always in erg mode as well. I use the Kicker as my power source for Trainer Road. Hmmm…

If it’s a reasonably modern unit it’s using firstbeat stuff not a best “insert time period here”.


I’ve done the ramp test a few times now and I have gotten significantly lower numbers v. Traditional 2 x 8. I don’t know why? I’ve shelled myself every time. I’m up for another test this week and I do plan on using the ramp test again, first. I’ll be surprised if the results are too much different but I will be doing it as fresh as possible and with a positive mindset!

I’m sure that’s what they use but in every case that I’ve done 8 minute+ efforts I get an estimate of new FTP. If we’re talking the automatic FTP-calculations that is. The real FTP-test is 2x8 mins but that’s just what I’ve heard. I’ve never tried it myself.

Never tried the built in guided FTP test. Too awkward to do on the roads.

The automatic calculation is a bit so so but mostly works on climby days in my experience as it requires sufficient ‘time in zone’ or more accurately sufficient time across zones during he ride. It’s also dependant on having a reasonable VO2 max estimate for you. That said there’s no particular reason it’s limited to 8 minutes and from my experience of the data I don’t believe that’s what it’s doing.

fwiw I’ve found the garmin ftp guess on the 520+ to be remarkably similar to the figure from the ramp test. As somebody mentioned above, within a very few watts difference.

I haven’t done the actual garmin ftp test I’m just talking about the “a new ftp has been detected” auto generated thing

1 Like

Yup. Also if you install the xert what is my FTP connect IQ field it will be within the error bars at the end of a ramp test (though a touch higher than TR).

Garmin/Firstbeat’s FTP autodetect picks up the inflection point in Heart Rate Variability typically associated with lactate threshold, rather than the power held over a set period of time.

Personally I find the autodetect consistently reports an FTP 10-15 watts lower than what I can achieve in a 20 minute test. Fortunately Garmin will take the 20 min test (if it’s available) over the autodetect method.


FWIW I’ve found Garmin’s FTP prediction to be pretty close to my own threshold tests.


Yep, that’s what I’m referring to. Thanks everyone!

thanks, and from another thread just realized my Tickr HRM doesn’t send HRV data over ANT+ (only over Bluetooth). I switch back and forth between Garmin and Tickr HRMs, although I prefer the Garmin as its slightly more comfortable.

Didn’t know that about the tickr - I have one stashed away in a drawer somewhere. Won’t bother using it if that’s true

1 Like

might have seen the “Tickr HRV only on BT” comment on DCRainmaker site… Here is link with some info: Heart Variability Monitors and Elite HRV Compatible Monitors

1 Like

Thanks for that - I’ve also read that the wahoo speed sensor isn’t as accurate as the Garmin. They recommend you don’t use it for the Aeropod as it gives wonky results in their testing

Prob best avoid the wahoo sensors

It could be due to using different power sources. Not sure how similar the readings from each meter are but for me, I have a Garming Vector 3S (single side) and a Wahoo Kickr Core and if I don’t powermatch, the Kickr is usually average of 10-20 watts lower. So that could be part of the reason you see a variation of similar margin in your FTP readings.

This is the worst thing about Garmins, the bloated features that only a small number of people actually use. Would be nice if you could customize which options exist in the menu’s using an app, for example. Just to keep things nice and clean.

I’m really glad we’re talking about this! Myself and a fellow club rider like to joke every time Garmin tells us that our FTP went up: “Garmin FTP LOL”. For myself and my Edge 820, it really feels like their VO2MAX and FTP estimates are waaaaay too high, and I’ve always wondered how they were making their estimates.

For example, as a 43 year old male, it has my FTP as 250 and my VO2MAX as 49. The VO2MAX number is notable (hysterical?) because that puts me in the “superior” category for my age group; the only thing superior about me is the level of allergies and asthma that I have to deal with. If I calculate my VO2 using my 6 minute power and weight, I get 41.2, which puts me squarely in the “good” category.

Garmin’s FTP number is also very much a “LOL I wish” number, as well. I did Kaweah, on Saturday, with my FTP set at 230 and I had to take 30 second backspins halfway through each 10 minute threshold interval. If I had set my FTP at 250 I would be dropping the intensity, immediately.

Someone mentioned that Garmin calculates based off of smaller time segments, but do we have any idea what they’re actually doing, and why their numbers seem so off from TR and the math?


some info here:

as it requires stable vo2max estimate, you also need to look here:

My Garmin 520 estimates of vo2max and FTP estimates have been quite good. On the FTP side, during a phase with increasing ftp I’ve received same-ride notifications from Garmin and TrainingPeaks. For vo2max and FTP, I’ve used WKO software to go back and see the Garmin estimates (using Firstbeat technology) are in sync with WKO estimates (using modeled Power Duration Curve). So I’ve been pretty happy in the past. Haven’t done a more formal 20+ minute test since buying the 530 two months ago, will let you know if my opinion changes.