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Plus, why other metrics are worthy of your attention instead.

While many runners don’t love the treadmill, there are times when its use is definitely warranted. For example, when the weather is atrocious, or it’s too dark to feel safe running outside, taking your run indoors can come in handy.

The treadmill also does indeed provide some legit benefits, such as helping you tackle speed work, keeping you consistent with a certain pace, and helping you incorporate more hill training into your routine when you don’t live near hills. Another perk of treadmills: They track certain stats, like calories burned, distance traveled, and average pace, which may be appealing if you like to keep tabs on your performance but don’t enjoy running with a fitness watch.

But if you’ve ever noted the calories burned at the end of your treadmill session, you may have questioned the accuracy of that measurement. Did Tuesday’s speed workout really torch 800 cals?

We tapped two experts to understand the accuracy of treadmill calorie counts. Below, everything you need to know, including why runners shouldn’t put all their focus on calories in the first place.

It’s hard to say exactly how accurate treadmill calorie counters are because each treadmill manufacturer potentially has their own formulas that they plug into the machine, says Janet Hamilton, C.S.C.S., exercise physiologist and running coach with Running Strong in Atlanta. But in general, they’ll use metrics like speed, incline, and distance to tabulate how many calories you expend.

On the whole, treadmill calorie counts are not very reliable, says Alyssa Lombardi, exercise physiologist, running coach, certified personal trainer and founder of Alyssa_RunFit Coaching. That’s because they don’t typically take into account all the information needed for an accurate reading, including gender, age, height, weight, body size, muscle mass, and fitness level.

If your treadmill tracks your heart rate, you might also think that helps boost the accuracy of the reading. But while heart rate is a good measure of the intensity of your workout (which thus impacts calories burned, with a higher heart rate associated with greater energy expenditure), there are a number of other things that influence your heart rate, including temperature, body position, certain medications, how much food you’ve eaten, what muscles you’re working, and whether you’re exercising continuously or in bursts, according to the American Council on Exercise (ACE). So while heart rate data can enhance the accuracy of your treadmill’s calorie counter, it’s not a totally trustworthy metric.

Whether you hold onto the handrails while running can make a difference, too. Gripping those bars will greatly overestimate cals burned because the support reduces the actual work you’re performing, ACE reports.

Of course, if you input stats like your age, gender, height, and weight into a treadmill, that will likely give you a more accurate estimate, but it still won’t be 100% because the machine doesn’t know your body or your effort.

Moreover, most gym treadmills don’t get calibrated on a regular basis, says Hamilton, meaning the speed the treadmill says you’re running may not be spot-on, and that discrepancy could influence the accuracy of the calorie count. This probably wouldn’t make a big difference though, caveats Hamilton.

There isn’t a ton of research on the accuracy of calorie counts on treadmills specifically, but studies on exercise machines have found them to be imprecise on the whole. A study published in 2018 involving elliptical machines, for example, found the equipment significantly overestimated calories burned, tacking on more than 100 extra calories for a 30-minute workout.

The bottom line: Take treadmill calorie counts with a grain of salt, as they’re almost certainly not spot-on and in some cases, could be way off.

Having a fitness watch that has access to your previous exercise and fitness level, as well as the ability to continuously track your heart rate, like an Apple Watch or Garmin, is going to be a bit more accurate than a treadmill, says Lombardi. Some of these devices also use personalized metrics like your weight, height, age, and gender to make more accurate calorie estimates than treadmills.

However, one study published in 2017 concluded even these devices aren’t fully reliable. The study examined heart rate and energy expenditure accuracy of the Apple Watch, Fitbit Charge HR, and Garmin Forerunner 225 and found that most over estimated energy expenditure. Another study, also published in 2017, examined the accuracy of wrist-worn fitness devices, including Apple Watch, Basis Peak, Fitbit Surge, Microsoft Band, Mio Alpha 2, PulseOn, and Samsung Gear S2. It also came to the conclusion that even though heart rate was adequately measured, energy expenditure was not.

Finally, a study published in 2019 examining fitness watches and the accuracy of the VO2 max data and calories burned also concluded that the devices didn’t offer up valid numbers. (A caveat: All of these studies involved fewer than 100 participants and with fitness watch technology consistently improving, accuracy could be higher. But we need more research to confirm.)

One thing that can throw off the accuracy is the quality of the heart rate data. For example, on the Apple Watch, heart rate readings can be influenced by a number of things, according to the brand, including how snugly the watch fits against your skin, the temperature you’re exercising in, and whether you have tattoos.

Another option for getting a more accurate calorie count than on a treadmill is to use an online calculator to input details like your height and weight, as well as the intensity and duration of your run. The calculator will then provide you an estimate of how many cals you’ve torched. Keep in mind though, the estimate is just that—an estimate.

To get the most accurate measurement of calories burned, you’d have to wear, for your entire run, an oxygen uptake analyzer—basically, a gas mask-like device with a little backpack attached, says Hamilton. The analyzer would track, breath by breath, how much oxygen you’re taking in and how much carbon dioxide you’re expelling. That data would provide a good read on your metabolism while exercising, which would ultimately be used to calculate how many calories you burned.

Of course, wearing such a device for every run is both uncomfortable and impractical, so most of us will instead rely on more general calorie counters, which are best considered as a general estimate and not the end-all, be-all.

If your goal is weight loss, then it may be appropriate to closely track how many calories you burn. But for many runners, it’s not a stat that warrants close monitoring.

Hamilton says calories expended during a run are usually the last metric she cares about as a running coach. “The number of calories you burn on the treadmill is way less important to me than the distance that you cover and the pace that you’ve covered it at,” she explains.

Additionally, “as runners we need calories as fuel,” says Lombardi. “If we are focused on the calories we are burning, we could start to develop a negative mindset around calories and food.” This could cause you to not eat enough calories to fuel your running. And that will only harm your miles—not help them.

So while it’s totally fine to note your treadmill calorie counts, you’re better served directing your focus toward more reliable, beneficial metrics that show your progress, like speed, distance, and duration. Or simply how good you feel and the confidence you experience having crushed a tough workout when you step off that treadmill.

Jenny is a Boulder, Colorado-based health and fitness journalist. She’s been freelancing for Runner’s World since 2015 and especially loves to write human interest profiles, in-depth service pieces and stories that explore the intersection of exercise and mental health. Her work has also been published by SELF, Men’s Journal, and Condé Nast Traveler, among other outlets. When she’s not running or writing, Jenny enjoys coaching youth swimming, rereading Harry Potter, and buying too many houseplants. 

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