As well as delivering immersive experiences, VR gaming has another welcome, if unintended side-effect: getting players fit. The Virtual Reality Institute of Health and Exercise wants to show you how.

When using high-end VR headsets like the HTC Vive and Oculus Rift players are often utilizing their whole body. They might be waving position-tracked controllers to swing swords, using positional tracking to dodge attacks, or walking with room-scale locomotion to explore their surroundings. In some more intense experiences you can find yourself inadvertently working up a sweat; just this year I’ve found myself gasping for air after long games of Gorn, Dick Wilde, and Paulo’s Wing. In fact, some people have already used VR to lose massive amounts of weight.

The problem is it’s hard to know just how much exercise you’ll get playing a game until you try it. Some fans might be more inclined to pick up an action game, for example, if they know they’ll get a good workout while having an intense gaming experience.

To that end, the San Francisco-based Institute is today revealing its own ratings system that judges how many calories the average user will burn during a minute of play time.

Obviously it’s impossible to judge the capabilities and fitness of everyone playing a VR game as well as the difficulty modes they select, so the institute’s methodology makes a few assumptions, like assuming players will not avoid movements when playing, but also not go out of their way to obtain success. Ratings are based on metabolic rate (MET score) during resting, from which calorie estimates are generated based on the general user. The exercise’s intensity is also compared to other activities like walking, sprinting, swimming and, for controller-based games, resting. All of that information is then condensed into one easy to read label that developers can use to promote their games or users can search through on the group’s website.

Take note that raters don’t play the entire game but instead a representative sample that’s observed. Their peak MET score is recorded to express the best possible circumstances and their averages are observed over testing for extra clarity. In some cases, games are observed twice.

The group has already given ratings to some of VR’s most popular experiences. Superhot VR, for example, is said to be the exercise equivalent of walking, burning between two to four calories per minutes. Audioshield, meanwhile is much more strenuous, burning eight to 10 calories a minute and compared to rowing. So far it looks like boxing simulation Thrill of the Fight is the most intense workout, burning 15 calories per minute. Me? I think I’ll stick to Gorn’s four to six calories per minute workout.

Developers are encouraged to submit their own games, but the group will self-rate apps that look like they could be intensive too.

So next time you’re on the hunt for a new VR game, maybe take a look to see if it’s got its own fitness rating too.