Have you ever hopped onto your Zwift Ride, ready to crush a workout, only to have a mini heart attack at the FTP number Zwift has decided is right for you? Yeah, me too! It’s like Zwift is saying, “Surprise! You’re 15 watts stronger than you thought!” Thanks for the vote of confidence, but I’m not sure I’m ready for that kind of pressure!
Surprise! You’re 15w stronger than you thought!
Okay, so you’re scratching your head wondering why your Zwift Workout FTP and that mysterious zFTP are playing a game of “guess who’s the real FTP?”
Let’s break it down in a way that doesn’t require a Ph.D. in virtual cycling.
Workout FTP: Your Friendly Neighborhood FTP
Think of your Workout FTP as the number you actively tell Zwift about yourself. It’s like updating a social media profile. You usually get this number one of three ways:
The FTP Test
You suffer (a lot!) in a 20-minute test or a ramp test, and Zwift, being the good friend, takes 95% of your best 20-minute power and says, “Okay, this is your FTP!”
The Manual Entry
You flex your muscles and confidently type in a number you think is right. (Hopefully, you’re not just giving yourself a little “bonus” for extra motivation!)
The “Oops, I Did It Again” Moment
You accidentally crush a 20-minute power best during a ride or race, and Zwift pops up, asking if you want to update your FTP. If you click “Yes!”, congratulations, you’ve increased your FTP!
Basically, this Workout FTP is the number Zwift uses to make your workouts challenging—but hopefully not too challenging! If it thinks you can handle more, it’ll bump up that FTP to keep things spicy!
zFTP: The Secret Agent FTP
Now, zFTP is a bit more sneaky. It’s like Zwift’s own private investigation into your fitness. Instead of just relying on one test, it’s constantly analyzing your power data from the last 90 days like a detective piecing together clues.
zFTP is calculated using a more complex model that looks at your best efforts across multiple durations. Your 30-second sprints, your 12-minute climbs, your 30-minute slogs…it considers everything! Then, it uses some algorithm magic to estimate what your “critical power” actually is.
So, why does Zwift do this?
Well, zFTP is primarily used behind the scenes. It’s how Zwift decides what category you’re allowed to race in (to prevent sandbagging!) and it’s used on ZwiftPower for race results.
It’s basically the “fitness police” keeping things fair(ish).
The Key Differences
A lot of Zwifters have noticed that their zFTP is usually a bit shy compared to their FTP—think of it as the cautious sibling who always rounds down just to be safe. We’re talking differences of 3–5% or sometimes even more.
For example, if you crush a 20-minute effort at 150W, Zwift will proudly declare your FTP as 142W (because, math: 95%). But your zFTP? Unless you’ve shown the algorithm some epic long-haul heroics, it might only tiptoe up to 130–135W.
Of course, there are outliers—if your power curve is flatter than a pancake or you love riding at threshold for ages, your zFTP can catch up to or even outpace your FTP. But for most of us mere mortal OWLs, zFTP tends to play it safe and stay a little lower.
The big takeaway is that you actively set your Workout FTP, while zFTP is a passive estimate Zwift calculates for other purposes. You use Workout FTP for training, and Zwift uses zFTP for competition categorization. They’re both FTPs, but they have different jobs!
In short: Zwift isn’t broken—just a little quirky with its math!
So, if you find yourself gasping for air during a workout, just remember: Zwift believes in you—even if you’re not quite ready to believe in yourself yet!
Zwift believes in you—even if you’re not quite ready to believe in yourself yet!
One final tip…
If your Zwift Workout FTP is more than 5% higher than your zFTP, feel free to change it! Setting your FTP on Zwift manually is a breeze:
- Fire up Zwift.
- On the Home Screen, click your initials, then hit My Profile.
- Type in your chosen FTP number (go ahead, be optimistic!) and smash that SAVE button.
Now, hop on for a couple of hard rides or jump into a race. If you manage to outdo the FTP you set, you’ll see an FTP Increase Detected pop up giving you a little “congrats, you’re stronger than you thought!” moment.
Remember, whether you’re setting your FTP or just enjoying a slow pace OWL Grey Zone Trivia ride— keep pushing those pedals—and don’t forget to enjoy the ride!
