How Garmin estimates VO2 max - and whether the calculation is accurate

VO2 max is the maximum volume of oxygen you can absorb per minute per kilogram of body weight at your peak - and almost every Garmin watch can calculate this figure automatically.

We have a dedicated guide that explains why VO2 max is an essential metric for runners, cyclists, and anybody seeking a gauge of their aerobic fitness.

However, there are some specifics to understand if you're using Garmin's calculation to track your VO2 max.

Below, we'll explain exactly how Garmin calculates its VO2 Max Estimate for running and cycling - and whether it's actually accurate.

How Garmin calculates VO2 max

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Garmin is pretty cagey about how it specifically gathers its VO2 Max Estimate, which makes sense given that each manufacturer uses a proprietary algorithm for calculating the metric.

It also varies slightly based on your device and the type of activity you're tracking.

Nevertheless, we know methods typically require your Garmin watch's heart rate data (or paired HRM data) to be elevated to 70% of your maximum heart rate for a certain period. We'll cover them in more detail below.

The most detailed explanation of how Garmin calculates VO2 max comes from its analytics arm, Firstbeat Analytics:

"The calculation relies on a combination of personal background information and data collected during your activity. This includes a focus on heart rate and running/walking speed," they say.

"Movement speed and heartbeat data are used to investigate the relationship between internal and external workloads. In other words, how hard your body is working to produce your performance."

How to get a VO2 Max Estimate for running

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While specific VO2 Max Estimate values can be given for trail running and ultra running - providing you have a compatible watch - we suspect most people will be interested in the calculation for regular running.

You'll have to use the 'Run' profile to obtain an estimate, though the requirements vary slightly depending on your watch.

For example, the Venu, Vivo, and Lily smartwatch lines calculate VO2 max slightly differently from the company's Forerunner devices.

We've consolidated these to ensure you can gain a VO2 Max Estimate for running no matter the Garmin watch you own (assuming it's compatible with the feature):

• Running activity must be 15 minutes or longer
• The activity must take place outdoors with a GPS signal
• The activity includes HR data from the watch or paired chest strap
• Heart rate data must be at least 70% of max HR for 15 minutes or longer

How to get a VO2 Max Estimate for cycling

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Garmin notes that you'll need to maintain a steady effort to receive a specific VO2 Max Estimate for cycling - and also recommends using an indoor trainer if you're struggling to obtain one. 

These are the official requirements:

• Cycling activity must be 20 minutes or longer without stopping
• Heart rate data must be collected from the watch or a connected chest strap
• Heart rate data must be at least 70% of max HR for at least 20 minutes continuously
• Power meter data must be collected during the workout

Is Garmin VO2 max accurate?

When analyzing the accuracy of Garmin's VO2 Max Estimate, it's important to remember that the feature is just that - an estimate. 

With that said, Garmin (via Firstbeat Analytics) does suggest that the feature is plenty accurate enough to be used as a guide of VO2 max:

"Firstbeat Analytics can automatically detect your VO2max fitness level during walking and running activities, using a proprietary method shown to be 95% accurate compared to laboratory measurements."

Like most of Garmin's insights, the accuracy of the VO2 Max Estimate also improves the more data you feed it.

Given it relies somewhat on accurate heart rate data, too, we think pairing a chest strap is likely to lead to a better result - or, at the very least, wearing your watch correctly.