Understanding VO₂ Max on Your Garmin: What It Means and How to Move the Needle

You finish an honest tempo run on a humid morning, sync your watch, and your VO2 max has dropped a point. Last month it ticked up into "Excellent" and you felt great about it. Neither moment means as much as it feels like it does.

Here is what the number is, how your Garmin works it out, how far to trust it, and what training actually moves it.

Photo: SportPlus.sg / Isis Ang

Garmin VO2 Max at a Glance

What the Number Means

Garmin defines VO2 max as the maximum volume of oxygen, in millilitres, you can consume per minute per kilogram of body weight at your maximum performance. Its Forerunner 265 manual calls it an indication of athletic performance that should increase as your fitness improves.

The estimate comes from Firstbeat Analytics, and the ratings that turn your number into Poor, Fair, Good, Excellent or Superior are used with permission from The Cooper Institute. In Garmin Connect you can see where your score ranks for your age and sex.

How Your Watch Works It Out

What the Watch Needs from You

• Run Outdoors: The estimate needs GPS. Indoor runs do not generate a VO2 max estimate.
• Put in Some Effort: Garmin asks for at least 10 minutes at a moderate or high intensity, reaching at least 70% of your maximum heart rate.
• Set Up Your Profile: For the most accurate estimate, Garmin says to complete your user profile and set your maximum heart rate.
• Leave Out the Trails if You Like: You can turn off VO2 max recording for trail and ultra runs, so slow, hilly outings do not drag the number down.

Give It a Few Runs

Garmin says the estimate may seem inaccurate at first, because the watch needs a few runs to learn about your running. A new watch, or a long break, means early readings are worth less.

Heat and Humidity

Garmin's watches show heat and altitude corrected VO2 max values when you are acclimating to high heat or high altitude. That helps in Singapore, but a hot, hard run can still look like a bad day on your wrist. One reading after a humid tempo session is not a loss of fitness.

Follow the trend over several weeks, not the number after one humid run.

How Accurate Is It?

A 2022 meta-analysis of 14 validation studies in Sports Medicine found that watches estimating VO2 max from exercise were close on average across a group. For individuals, though, the limits of agreement ran to roughly 10 mL/kg/min either side of the lab value.

A 2026 study of 35 endurance athletes tested a Garmin Forerunner 245 against a lab and found it underestimated VO2 max, with average errors of 7.9% and 7.2% across two runs. Our article on lab testing vs your watch covers the research in more detail.

So the number on your wrist is good for spotting direction: whether your fitness is rising or slipping over a block. It is less reliable as an exact figure to compare with a friend's.

How to Raise It

Keep Most of Your Running Easy

A 2010 review by Stephen Seiler of how top endurance athletes train found they converge on about 80% of sessions at low intensity, with about 20% dominated by high-intensity work such as intervals at around 90% of VO2 max. Easy running is where most of the volume comes from.

Add Some Hard Intervals

In a 2007 study, 40 moderately trained men did one of four programmes three days a week for eight weeks. The group running 4 x 4 minutes at 90–95% of maximum heart rate, with 3 minutes of active recovery at 70% between efforts, raised VO2 max by 7.2%. High-intensity intervals improved VO2 max significantly more than long slow running or threshold running with the same total work.

Be Patient

The study above ran for eight weeks. Give any change in training at least that long before judging it on your watch.

When a Lab Test Is Worth It

If you want a measured figure rather than an estimate, or zones built from your own data, a lab test is the next step. FORGED by ReFormd runs a VO2max Test at 1 Raffles Link, #B1-23 CityLink Mall, bookable on ATHLO+.

Track Your VO2 Max with Garmin on ATHLO+

Browse the Garmin range on ATHLO+, including the Forerunner 265, to follow your estimate through a training block.

Ready to set the zones that make your easy runs easy? Read Heart Rate Zones Explained next.