Fitbit VO2 Max: Where to Find It, How Accurate It Is, by Model
Run these workouts on your iPhone, or hands-free on Apple Watch. Get PEAKVO2 Yes, Fitbit tracks VO2 max. It calls the estimate your Cardio Fitness Score, and since May 2026 it lives in the Google Health app (the renamed Fitbit app): open the Today tab, tap the heart rate tile, and scroll to Cardio Fitness. Every current Fitbit estimates it from your resting heart rate and profile; models with GPS sharpen the estimate using your outdoor runs, and validation research shows that run-based estimates land within about 10 percent of a lab test. The new screenless Fitbit Air tracks it too, for $99 with no required subscription.
If you have never checked yours, that score is one of the most useful numbers your Fitbit produces. VO2 max, the maximum rate at which your body can use oxygen, is the single best measure of cardiovascular fitness and one of the strongest predictors of long-term health (Mandsager et al., 2018). Here is where to find it, what it means, how each Fitbit model calculates it, and what to do with it.
Where to Find Your VO2 Max on Fitbit
Fitbit reports VO2 max as your Cardio Fitness Score, in ml/kg/min just like a lab test, alongside a Cardio Fitness Level that ranks you from Poor to Excellent against people of your age and sex.
- Open the app. Since May 19, 2026 the Fitbit app is called Google Health; your data and score carried over with the rebrand.
- From the Today tab, tap the heart rate tile.
- Swipe or scroll to Cardio Fitness to see your score, your level, and the trend over time.
If you only see a range (for example 42-46) instead of a single number, that is Fitbit telling you it has estimated your score from resting heart rate alone. To narrow it, record at least one outdoor run with GPS, and the estimate switches to the more precise method below.
Fitbit Air: VO2 Max Without a Screen or a Subscription
The biggest Fitbit news in years came in May 2026: the Fitbit Air, the first genuinely new device after a release drought through all of 2025, and Fitbit's direct answer to Whoop. It went on sale May 26, 2026 for $99, and the headline is the business model as much as the hardware: where a Whoop band is a paperweight without its membership (from roughly $199 a year), the Air's core health tracking works with a one-time purchase. That is the first time a major tech company has attacked Whoop's subscription model head-on, and it is why the launch got so much attention.
The device itself is a screenless 5.2-gram pebble that sits in a woven band, about 25 percent smaller than a Fitbit Luxe and 12 grams all-in, light enough to forget on your wrist and in your sleep. Inside are an optical heart rate sensor, accelerometer, and skin temperature sensor; charging is USB-C, and five minutes of it buys about a day of battery. There are no buttons and no display: everything the Air measures, from sleep stages and HRV to stress and workouts (SmartTrack auto-detects runs, walks, and rides; 40+ modes can be started from the phone), lives in the Google Health app.
For this article the key question is what the Air does for VO2 max, and the answer is better than its price suggests:
- It reports a full Cardio Fitness Score, same as every other Fitbit, in the Google Health app.
- It runs the Pixel Watch 4 algorithms for VO2 max and HRV, so the estimation logic matches Google's current flagship watch rather than the older tracker generation.
- It has no built-in GPS. Like the Inspire 3, it needs your phone along on outdoor runs to feed the precise pace-to-heart-rate method; worn daily without runs, it gives you the resting-heart-rate estimate.
Two honest caveats to the no-subscription story. The advanced layer, including the Gemini AI coach and the Daily Readiness Score, still sits behind the optional Premium tier, so the free experience is the raw metrics rather than the coaching. And the lack of any screen means no glanceable heart rate mid-workout, which matters exactly in the hard intervals where you want to know your zone: you will be training off your phone, which is where a guided interval app carries the session.
Who is the Air for? Someone who wants Whoop-style 24/7 recovery and fitness data, including a VO2 max trend, without a screen on the wrist or a rolling bill. If you want the sharper run-based estimate without carrying a phone, the Charge 6 with built-in GPS remains the better pure VO2 max tool.
How Fitbit Calculates VO2 Max
Fitbit uses two methods, and knowing which one your score comes from matters for how much to trust it.
Resting heart rate method (all models). Without GPS runs, Fitbit estimates your score from resting heart rate, age, sex, weight, and profile data. This is the same logic as the Uth-Sørensen resting heart rate formula in our VO2 max calculator: a lower resting heart rate generally means a fitter heart. It produces a reasonable ballpark and a wide range, but it never sees you actually exercise.
Run-based method (GPS models or phone GPS). Once you record outdoor runs, Fitbit analyzes the relationship between your pace and your heart rate: covering more ground at a lower heart rate means a higher VO2 max. This is the estimate worth paying attention to, and it is the one the validation research tested.
Fitbit VO2 Max by Model
Every current Fitbit shows a Cardio Fitness Score, but the quality of the estimate depends on GPS. Here is the lineup as of mid-2026.
| Model | GPS | VO2 max estimate |
|---|---|---|
| Charge 6 | Built-in | Best tracker option: run-based estimate without your phone |
| Sense 2 | Built-in | Run-based estimate without your phone |
| Versa 4 | Built-in | Run-based estimate without your phone |
| Fitbit Air (2026) | Phone GPS | Screenless band; VO2 max from phone-GPS runs, Pixel Watch 4 algorithms |
| Inspire 3 | Phone GPS | Resting-HR estimate; improves if you run with your phone |
| Luxe | Phone GPS | Resting-HR estimate; improves if you run with your phone |
| Pixel Watch 3 / 4 | Built-in | Full Fitbit health stack including Cardio Fitness Score |
Context on that lineup: Fitbit released no tracker at all in 2025, then 2026 brought the Google Health rebrand, the Gemini AI coach as a paid add-on, and the screenless Fitbit Air covered above.
If you are choosing a tracker specifically for VO2 max, the Charge 6 is the value pick and the Pixel Watch 4 the premium one; our fitness tracker comparison ranks Fitbit against Garmin, Apple Watch, and the rest.
How Accurate Is Fitbit's VO2 Max?
More accurate than its reputation suggests, provided you feed it runs. Two peer-reviewed validation studies tested Fitbit's estimate against laboratory VO2 max measurement:
- Run-based estimates are solid. In 65 adults who each recorded a qualifying outdoor run, the Fitbit Charge 2's estimate showed a bias of only 0.3 to 1.6 ml/kg/min versus the lab value, with a mean absolute error under 10 percent, and the authors concluded the measure has "an acceptable level of validity" in young, healthy adults who run (Klepin et al., 2019).
- It skews slightly optimistic. A separate study of 30 young adults found Fitbit overestimated lab-measured VO2 max on average (52.5 vs 49.9 ml/kg/min) (Kwon et al., 2019).
The practical reading: treat the absolute number as roughly plus or minus 5 ml/kg/min, assume it flatters you by a point or two, and trust the trend. A score that climbs over eight weeks of training reflects a real improvement, and the trend is exactly what Fitbit measures consistently. That advice applies to every wearable, and Fitbit sits mid-pack for accuracy: Garmin leads in head-to-head validation, with Fitbit and Apple Watch close behind.
If you want a second opinion on your number without a lab, run a Cooper test and enter the result in our VO2 max calculator, or book a lab test near you for the real measurement.
Is Your Score Good? Check the Chart
Fitbit's Poor-to-Excellent levels already adjust for age and sex, but they compress a lot of information into one word. To see exactly where you stand, look up your score in the VO2 max charts by age and sex: the same ACSM and Cooper Institute norms used in clinical exercise testing, decade by decade.
As a quick anchor: for men a good score is roughly 46+ in their 20s, 42+ in their 40s, and 35+ in their 60s; for women the thresholds run 10 to 15 percent lower.
How to Raise Your Fitbit VO2 Max
Your Fitbit measures the number. Raising it takes structured training, and the evidence points clearly at high-intensity intervals: in a controlled trial, two weekly Norwegian 4x4 sessions raised VO2 max by 7.2 percent in eight weeks (Helgerud et al., 2007), and most people can gain 5 to 15 percent in 8 to 12 weeks with consistent interval work. The full method is in how to improve your VO2 max.
The workout itself is simple: four minutes hard at 90 to 95 percent of max heart rate, three minutes easy, four times through. You can run one right now in the browser timer. And this is where PEAKVO2 pairs naturally with a Fitbit: the app guides the intervals on your iPhone with automatic phase transitions and your target zone for each phase, you train, and your Fitbit watches the Cardio Fitness Score climb.
PEAKVO2. The interval app for your cardio fitness.
Guided Norwegian 4x4, Tabata, and HIIT sessions on iPhone and Apple Watch, with your target heart rate zone each phase. Your Fitbit tracks the score; PEAKVO2 runs the training that moves it.
Download PEAKVO2Frequently Asked Questions
Does Fitbit measure VO2 max?
Yes. Fitbit estimates VO2 max and reports it as your Cardio Fitness Score, in ml/kg/min, inside the Google Health app (formerly the Fitbit app). All current models estimate it from resting heart rate and profile data; models with GPS refine it using the pace-to-heart-rate relationship from your outdoor runs.
Where is VO2 max in the Fitbit app?
From the Today tab, tap the heart rate tile and scroll to Cardio Fitness. You will see your score or score range, your Cardio Fitness Level for your age and sex, and the trend over time. Since May 2026 the app is called Google Health; the path is the same.
How accurate is Fitbit's VO2 max?
With outdoor GPS runs recorded, validation research found a bias of only 0.3 to 1.6 ml/kg/min versus laboratory measurement and a mean error under 10 percent. Without runs, the resting heart rate estimate is a rough ballpark shown as a range. One study found Fitbit overestimates slightly on average, so treat the absolute number with a grain of salt and watch the trend.
Why is my Fitbit VO2 max shown as a range?
A range means Fitbit is estimating from resting heart rate and profile data only. Record at least one outdoor run with GPS (built-in on Charge 6, Sense 2, Versa 4, and Pixel Watch; via your phone for Inspire 3 and Luxe) and the estimate narrows to a single, more reliable number.
Which Fitbit is best for VO2 max?
Any model with built-in GPS gives the better run-based estimate without needing your phone: Charge 6 among the trackers, Pixel Watch 3 or 4 among the watches. Inspire 3, Luxe, and the Fitbit Air can match them if you carry your phone on runs. The estimate quality is the same once GPS runs are recorded.
Does the Fitbit Air track VO2 max?
Yes. The screenless Fitbit Air (released May 2026, $99, no required subscription) reports a full Cardio Fitness Score in the Google Health app, using the same VO2 max algorithms as the Pixel Watch 4. It has no built-in GPS, so bring your phone on outdoor runs for the more precise run-based estimate; otherwise you get the resting-heart-rate version.
Why did my Fitbit VO2 max go down?
Common causes: a stretch without training (VO2 max genuinely declines within weeks of stopping), weight gain (the score is per kilogram of body weight), runs in heat or hills that skew the pace-to-heart-rate relationship, or simply an updated estimate after new data. If the drop persists across several weeks of normal training, read our guide on why VO2 max drops.
Can I improve my Fitbit Cardio Fitness Score without running?
Yes. The score responds to anything that improves your cardiovascular fitness: cycling, rowing, brisk incline walking, or interval training. Note that without GPS runs Fitbit falls back to the resting heart rate estimate, which still improves as your resting heart rate drops with training, just with less precision.
Keep Reading
- Best Fitness Tracker for VO2 Max: 6 Devices Compared
- Garmin VO2 Max: How It Works and How Accurate It Is
- How to Improve Your Apple Watch Cardio Fitness Score
- VO2 Max by Age: Chart of Normative Scores
- Norwegian 4x4 Protocol: Proven HIIT to Raise VO2 Max
- Why Did My VO2 Max Drop?
References
- Klepin K, Wing D, Higgins M, Nichols J, Godino JG. Validity of Cardiorespiratory Fitness Measured with Fitbit Compared to VO2max. Med Sci Sports Exerc. 2019;51(11):2251-2256. PubMed
- Kwon S, et al. Assessing the ability of the Fitbit Charge 2 to accurately predict VO2max. mHealth. 2019;5:39. PubMed
- Helgerud J, Høydal K, Wang E, et al. Aerobic high-intensity intervals improve VO2max more than moderate training. Med Sci Sports Exerc. 2007;39(4):665-671. PubMed
- Mandsager K, Harb S, Cremer P, et al. Association of cardiorespiratory fitness with long-term mortality among adults undergoing exercise treadmill testing. JAMA Netw Open. 2018;1(6):e183605. PubMed