View VO₂Max on your smartwatch and phone

Direct measurement of VO₂Max requires exercise testing equipment and respiratory gas analysis. Smartwatches increasingly estimate it from information such as the relationship between GPS-measured distance and exercise heart rate (Japan MHLW, 2023).

iPhone and Apple Watch

Apple says Apple Watch Series 3 and later estimate VO₂Max, displayed as Cardio Fitness. The iPhone is where you view the result.

Estimation requirements

• Estimates use how hard your heart works during Outdoor Walk, Outdoor Run, and Hiking workouts.
• Indoor workouts, including those using gym equipment, are not used.
• The first estimate may require at least 24 hours of wear and several eligible workouts.
• Age, sex, weight, height, and information about medication that may affect heart rate are also used.

Where to look

1. Open the Health app on iPhone.
2. Tap Browse → Heart → Cardio Fitness.
3. Switch between day, week, month, six months, and year to view the corresponding averages.

Limitations

• Apple Watch estimates values from 14 to 65 mL/kg/min.
• Age- and sex-based fitness classifications apply to people aged 20 or older. A low level may trigger a notification (notification criteria and interpretation).
• Conditions or medication that suppress heart rate may cause overestimation.

Apple: check cardio fitness (Japanese)

Fitbit and Google Pixel Watch

Google describes recording with Fitbit devices and Google Pixel Watch and viewing the result in Google Health. The former cardio fitness score is now called VO₂Max.

Estimation requirements

• Measurement is currently available only during outdoor runs with GPS enabled, not walking, cycling, or treadmill exercise.
• Record a 10-minute outdoor run for the first value. If one run is insufficient, up to three runs within 30 days may be needed.
• The calculation compares running efficiency—the relationship between pace and heart rate—with resting heart rate.

Where to look

1. Open the Fitness tab in Google Health.
2. Scroll to the key metrics section; use See all if needed.
3. Select VO₂Max.

Six fitness levels compare the value with people of the same age group and sex.

Google: view VO₂Max (Japanese)

Galaxy Watch

Samsung says Galaxy Watch measures VO₂Max during workouts and displays it in Samsung Health. The described requirements differ somewhat by model and software version.

• The Japanese Galaxy Watch9 product page specifies at least 10 minutes of outdoor brisk walking at 4 km/h or faster, or running. Results are reflected in the next day’s fitness index.
• The US support page, for models with One UI 4.1 or later, specifies a 10-minute run on flat ground at 4 km/h or faster, good GPS reception, and continuous heart rate monitoring enabled. It recommends starting the run from the smartwatch because automatically detected workouts may not produce a measurement. The result appears near the bottom of the workout summary.

Samsung: view workout results

Garmin

Compatible Garmin smartwatches estimate VO₂Max. Requirements appear in each model’s manual. The Instinct 2 series manual gives this example:

• Use wrist-based optical heart rate or an optional chest strap.
• Run outdoors with GPS reception for at least 10 minutes. Cycling also requires an optional power meter.
• Set your user profile and maximum heart rate correctly before measurement.
• The first estimate may be inaccurate; the smartwatch learns over several exercise sessions.
• Detailed data are available in Garmin Connect.

Where to look in Garmin Connect

1. Open Garmin Connect.
2. Open More at the bottom right → Performance Stats.
3. Open VO2 Max, the app’s label.

Check Garmin’s official instructions (Japanese) for the current display.

Other Android devices

Android’s Health Connect supports sharing health data between apps, including VO₂Max. Which apps can write or read VO₂Max depends on the app.

How accurate are smartwatch values?

A meta-analysis comparing wearable estimates with laboratory measurements included 14 studies and 403 participants, mostly young, physically active adults. It reported:

• Exercise-based algorithms: Average bias was close to zero (−0.09 mL/kg/min). The 95% limits of agreement, a statistical description of agreement at the individual level, were −9.92 to 9.74 mL/kg/min.
• Resting-data algorithms: Values were about 2.2 mL/kg/min higher on average. The 95% limits of agreement were −13.07 to 17.41 mL/kg/min.

The authors concluded that exercise-based algorithms were more suitable for group averages, but individual errors were large. Limits of agreement are neither the observed minimum and maximum nor a guaranteed bound for your error. This analysis did not include Apple Watch studies.

In an Apple Watch study with 30 participants and 28 included in the analysis, estimates obtained after five to ten days of wear were compared with direct measurements during maximal treadmill testing. Estimates were 6.1 mL/kg/min lower on average, with a mean absolute percentage error of about 13%. The 95% limits of agreement for measured minus smartwatch values were −6.11 to 18.26 mL/kg/min, showing substantial individual variation.

How to use the value

• Look at trends rather than one reading. Using the same smartwatch during similar activities and conditions makes changes easier to interpret. Google Health offers a past-three-month graph and monthly, quarterly, and yearly averages. Do not assume that small changes prove a change in fitness.
• Do not directly compare different models. Estimation methods differ between manufacturers and devices.
• If the value falls, check how you feel and the calculation conditions. Hills, indoor exercise, maximum heart rate settings, heat, and later stages of prolonged exercise may affect estimates. See reasons for a falling or unchanged value.
• App fitness levels use different comparison data. Each manufacturer selects its reference data; for example, Garmin manuals cite data used with permission from The Cooper Institute. These differ from the Japanese tables presented by MHLW, so the classifications may disagree.
• Do not overexert yourself to obtain a measurement. Rest when unwell. Stop immediately if chest pain, dizziness, or similar symptoms occur during exercise (safety guidance).

Compare a value with Japanese age-based values

Enter the displayed value in our comparison tool to compare it with Japanese age-group averages and reference values presented by MHLW. If you do not have a smartwatch, the same page also offers an estimate from resting heart rate.