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If you’re new to cycling training, you’ve probably never taken an FTP test. Heck, you probably have no idea what an FTP test even is! Let’s cover the basics of FTP, and options for testing it on Zwift.
What is FTP?
FTP is short for Functional Threshold Power. It’s the most commonly used metric of fitness for cyclists and measures the maximum power you can hold for longer durations (approximately 1 hour).
Going above your FTP will result in blood lactate levels increasing until you “blow up,” but if you’re fresh and well-fueled you should be able to ride at FTP for anywhere from 40-70 minutes.
Getting a bit more precise: while FTP is often described as the maximum power you can average for 60 minutes, that is not how it was actually defined by those who pioneered its use. Andrew Coggan defined it as, “The highest power that a rider can sustain in a quasi-steady state without fatiguing.” A sports testing lab would define it as the amount of power that can be put out at maximal lactate steady state (MLSS). MLSS is the highest exercise intensity you can hold where your blood lactate level remains constant over time.
Why Test Your FTP?
On Zwift, knowing your FTP is important because that figure determines the power requirements for intervals in structured workouts. If your FTP is set too low, you won’t get an adequate workout. If it’s set too high you won’t be able to hit your power targets.
Overall, FTP is the most popular metric for tracking fitness. Even if you don’t do structured workouts on Zwift, FTP is a single, simple metric that measures your capability as a rider.
How To Test Your FTP
Here’s the simple 4-step process used by most Zwifters:
- Kit up, boot up
- Pick a test from the workout options under Training>FTP Tests
- Follow the instructions on screen, destroying yourself in the process
- If your FTP increases, share it on Zwift Riders. If it does not, never mention this test to anyone. 🙂
Let’s take a closer look at the FTP test options Zwift provides.
3 FTP Tests on Zwift
FTP Test (Standard)
The standard FTP test is also the longest, at 45 minutes. It begins with a warmup that includes 2 blocks (3 minutes at 110% of FTP into 2 minutes at 120% of FTP) meant to take the snap out of your legs so your 20-minute test uses less anaerobic power and more aerobic power.
In this workout, the 20-minute test is all that matters. Your FTP result will be computed as 95% of the power you average during the 20-minute free ride interval.
One common question people have is how Erg mode works during the 20-minute test portion of this workout, because of course you wouldn’t want your trainer enforcing a particular wattage target during the test. And at the same time, you don’t want to feel gradient changes in Zwift, which would through off your pacing!
So it works like this: the 20-minute section is a “free ride” block, which in Zwift workouts means your trainer delivers steady resistance like you’re on flat ground, regardless of in-game terrain. So shift to whatever gear you’d like, where you can hold a comfortable cadence and hit the power numbers you’re trying to hit.
Once the 20-minute block finishes, the game will put you into a cooldown block, forcing you to hit the target wattage again like Erg mode normally does.
Watch Me Do An Older Version of the 20-Minute FTP Test:
Ramp Test
The ramp test starts easy, then simply increases your wattage by 20W every minute until you can’t pedal anymore. The nice thing about the ramp test is that you don’t have to worry about pacing yourself for a 20-minute effort. Just stay seated and pedal for all you’re worth, until you can’t pedal anymore! Typically the ramp test feels very easy at the start, but gets really difficult in the last 5 minutes.
Zwift will calculate your FTP once you stop pedaling. Your FTP Is calculated as 75% of the highest 1-minute power averaged during the test. If your new FTP is higher than your old one you’ll get a popup that says “New FTP set!” along with your new FTP value.
Watch Me to the Ramp Test:
Ramp Test Lite
If you don’t know your FTP but weigh less than 60kg/132lbs, or if you know your FTP and it is below 175 watts, you’ll want to take the “Ramp Test Lite” instead of the standard ramp test. This test starts at a lower wattage and increases by only 10W per minute, providing more accurate results for riders with a lower FTP.
Which Test is Best?
Everything about the ramp test is easier than the standard FTP test, but the downside is ramp tests can be less accurate, depending on your physiology. Specifically, riders with a higher anaerobic to aerobic power balance may have their FTP overstated by a ramp test.
On the other hand, the standard FTP test with its 20-minute all-out effort is very challenging, both mentally and physically. Additionally, newer riders will struggle to properly pace a 20-minute effort (they often blow up early).
Both styles of tests have their pros and cons, but generally speaking if you are a beginning cyclist and/or you want a quicker, easier test, go with a ramp format. If you want higher accuracy, and have the experience to pace yourself properly, go with the 20-minute format.
If you’ve never taken an FTP test, we recommend using the ramp test first. This will give you a fairly accurate FTP number, which you can use to pace yourself for the 20-minute test next time.
FTP Auto-Detection
For nearly 10 years, Zwift automatically detected your FTP in game by measuring your 20-minute power average as you rode, taking 95% of that value as your FTP. If it detected an FTP increase, you would get this screen:
But since December 2024, Zwift has been using an updated FTP detection algorithm that works for efforts 8-60 minutes in length. Read about how it works in these update notes if you’d like, but the important thing is to understand that Zwift automatically detects your FTP as you ride, and you’ll get a notification if it detects an increase. If you want your FTP detected accurately, simply do an all-out effort anywhere from 8 to 60 minutes in length.
Simple. But not easy.
Apart from Zwift, most cycling data platforms also compute an estimated FTP based on your ride data, even if you never take an FTP test. These calculated FTP figures are arguably more accurate than an FTP test, but it depends on how they’re calculated and what sort of efforts you’re feeding into their algorithms. Some of these platforms are free, while others may carry fees. Popular platforms include TrainerRoad, intervals.icu, XERT, and WK05 software.
Questions or Comments?
Share below!
In my opinion, any of the FTP tests are fine, as long as you do always the same type of test, so you see your relative improvement over the previous test.
Since this is just setting your ftp for the workouts, it being inaccurate towards the higher level (ramp tests), is preferable over underestimating your ftp because you’re new to FTP tests.
And for the juicy postings of your ftp numbers, you can then use the zFTP estimate, which is based on zwifts estimates, it’s generally more accurate than an overstated ramp test/failed 1 hour test.
shouldn’t this article also contain the Grade? The new way that Zwift can determine your FTP.
I think the grade uses the same formula as the 8-60 minute detection. The only difference is the grade tells you your ftp even if you haven’t clocked it higher than your current ftp; in my opinion it isn’t as accurate as the standard tests, or the other external sites (i use intervals.icu, would recommend)
Andrew is correct. The Grade’s algorithm is now used game-wide, so pointing people to The Grade seemed unnecessary. (It’s referenced quite a bit in the post linked under “FTP Auto-Detection” thought).
Does Zwift ever reduce your FTP? If you specifically select an FTP test workout then it should at least give you the option to update if the result is lower than it was.
It does not.
zFTP definitely adjusts downward, I just watched mine move a point lower from last week.
Yes for zFTP, since it’s based strictly on 90 day power numbers. I was talking about the in game FTP setting which this article is focused on.
Something I’ve always been uncertain about, Eric…
In the Standard FTP Test, presumably the warm up blocks are with Erg mode enabled and then it’s automatically disabled for the 20 min test?
Then, during the 20 min test is the trainer difficulty constant despite riding varying inclines? Or do you need to turn Trainer Difficulty to ‘Off’ before the workout?
erg mode is disabled for the 20 min, you need to shift gears yourself. pick a flat course unless you also want the hassle of managing power on inclining and declining sections of the road
My question was prompted by Eric not appearing to have any cadence or power variations at the hairpins (significant gradient changes), suggesting constant trainer load. Otherwise I couldn’t fathom why he’d chosen the Alpe.
I’ve done some reading since and found the 20 min free ride block in Zwift’s FTP Test applies a constant resistance, ignoring terrain.
ERG mode is disabled, but gradients are not simulated. So during the 20-minute section it basically feels like you’re riding on flat ground. (There are lots of workouts that do this. It’s the default behavior for free ride sections of workouts.)
Thank you for confirming, Eric @Eric Schlange I’d long-puzzled over this.
Something I’ve been confused about is whether you need to adjust the 20 min FTP output in Zwift to calculate your 60 min FTP or the FTP used in workouts. So for example, you average 100 watts in your 20 min test. Would you set your FTP for workouts to 100, or would you adjust it lower to a number that you could in theory sustain for an hour (and if lower, what’s the formula)?
Hi Danielle… there is just 1 ftp. The 20 minute test establishes it based on 95% of your overall average on the (20 minute) test. So in your example your ftp is going to be 95 for any workouts you do. And Zwift automatically records it after a test so you wouldn’t need to go into your profile to make adjustments.
Some people say the FTP tests should only be done seated, does this actually matter? I can ride out of the saddle for an hour and did the other day going up La Reine only sitting to catch my breath momentarily from time to time.. does it matter what you do or is this another consistency thing? IMO if my legs are producing the watts it doesn’t matter if I’m sitting or standing… but is there an official/professional opinion?
If you can go 60min full power staying out of saddle you can do the 20min test staying. 99% of people cannot. But if you know, then you can do the 60 min test as well 😅
My FTP Test has always been..Stayed Attached to the Front Group, and the Wheel in Front of Me!…Has always served Me well to achieve my Highest Power #’s 💪 😂
Why has Zwift changed the standard FTP test? They’ve now changed the usual 5m VO2 block for a mixed 3 minutes at 110% of FTP into 2 minutes at 120% of FTP. As it will drain the rider less, this will result in most having a bump to their FTP. Why change it when the old test was tried and tested and allowed all to compare apples to apples?
Rider attributes impacting the MAP (Ramp test) test also impacts the sustained effort test even with the blow out effort beforehand. From memory this is documented in the explanation for FTP “Training and racing with a power meter” (it was 1st published in 2006, so I don’t remember it as much as I once did) . Its not always 95% of the 20 minute effort, varying on the rider attributes. It could be 92% or 97%!
Purists would hate this (and I’m sure Dr Coggan as he was a regular on a forum I used to frequent): People think too much about the calculation of FTP as an absolute number that is fixed until their next test. Think of it more as the max potential you have demonstrated for that period. I think its good to use a range of sources (MAP/20min/1hr NP for a hard crit/ race efforts) and not lock yourself in to a magic number because it is daily impacted by uncontrolled variables. Acute and Chronic Training loads can help make test performance more repeatable/accurate through better prediction of recovery before the test.
You’ve got to show me the rider who can do 60min at 97% of 20min max power. 95% is already overestimating for 99% of riders as you correctly state.
Great write up. I have had Zwift for couple of years now, but only just beginning to look into it in detail and this was really helpful. Thanks.
Imho FTP = 75% of MAP ist usually too high. Its more towards 70-72% for most people. Likewise 95% of 20min Power is too high. Its more like 90-92%. Just look at typical power curves. It falls clearly more than 5% when time is tripled.
I find it hard to match the watts required , I am often above the required level, should I change to an easier gear to increase my cadence. I also notice my cadence does not match what I feel I am doing