Here's Why It's So Difficult to Measure the Calories You've Burned (and What to Focus on Instead)

When you’re drenched in sweat after a HIIT session or a long run, you might wonder how many calories you just burned after all that hard work. And while calories aren’t everything—you should also be focused on factors like the muscle tone you’re gaining and how you feel post-workout—the amount of calories you burn in a workout can help you assess how hard you’re working and ultimately help you lose weight (if weight loss is your goal).

Keep in mind, too, the amount of calories you burn in a workout is subjective—it’s going to be different for everyone based on your current weight, height, and fitness level. That said, we asked fitness experts to give us a general idea of the amount of calories you’d burn in a typical workout and how to gain the most accurate stats.

How Many Calories Do You Burn in a Typical Workout? 

Again, while it's difficult to list out how many calories each and every person would burn in a single workout, Froerer says the numbers below are the average calories burned by a 150-pound woman in a 30- or 60-minute workout. (To learn more about other factors which influence calories burned, see below.) 

• 60 minutes HIIT: 800 calories
• 60 minutes of running: 600 calories (10:00/mile pace)
• 60 minutes boxing: 560 calories
• 60 minutes weight training: 450 calories
• 30 minutes HIIT: 400 calories
• 30 minutes of running: 300 calories (10:00/mile pace)
• 60 minutes Pilates: 300 calories
• 30 minutes boxing: 280 calories
• 60 minutes yoga: 240 calories
• 60 minutes of barre: 220 calories
• 30 minutes weight training: 220 calories
• 30 minutes Pilates: 150 calories
• 30 minutes yoga: 120 calories
• 30 minutes of barre: 110 calories

Factors That Influence Calories Burned 

"Calorie burn is calculated based on a variety of both internal and external factors," Froerer explains. Below are some of the main elements at play.

• Body size and composition
• Age: "As you get older, it is common for the amount of muscle mass an individual has to decrease unless they diligently work to maintain it," Froerer says. As muscle mass decreases, overall body composition will show that fat mass will account for more of your total body weight. "This will lead to burning less calories at rest.”
• Sex: Men typically have lower body fat and more muscle mass than women—even of the same weight and age—which results in a higher caloric burn.
• Exercise selection: The more muscle engagement you have, the higher the calorie burn throughout the day.
• Intensity level: Generally, higher intensity workouts result in increased calorie burn. 
• Amount of daily physical activity: "Those who move more and stay active throughout the day tend to burn more calories than those who are sedentary," Froerer says. If your goal is weight loss, try to get extra steps in whenever you can.

How to Measure Calories Burned

If you're looking for a means to acutely measure the number of calories you've just burned from a workout, unfortunately, it’s challenging to get an exact number based on all of the factors above. "Generally, finding an accurate caloric burn from a specific workout is incredibly tough," says Miriam Fried, Founder and Head Trainer at MF Strong. 

"The caloric metrics you might find on a machine at the gym are just estimations based on average body weight, so it won’t be near accurate for most users. Even most studies on popular wearables currently on the market [ed. note: like fitness tracking devices] showed none were able to accurately track your caloric expenditure."

That doesn’t mean it’s not worth tracking, though. “It’s hard to measure the exact number of calories burned in a given workout, but many resources are available to provide close estimations,” Froerer explains. These include:

Heart Rate Monitor

If you want to go a bit more old school, invest in a heart rate monitor. “Your heart rate is one of the best physiological factors to determine how much effort it takes in order to perform a certain activity,” Froerer says. “Heart rate sensors are able to pick up this biological feedback and can then be used to calculate caloric expenditure.” Of course, now most fitness trackers have built-in heart rate monitors—but you can get a separate heart rate monitor to use while exercising if you wish. 

MET Value Charts

If you really want to level up and do a deep dive into calorie counts, look into MET, or metabolic equivalent charts. "These show a ratio of your working metabolic rate in relation to your resting metabolic rate," Froerer explains. "Metabolic rate is the rate of energy expended per unit of time and a good way to estimate how many calories are burned during a specific physical activity."

One MET is the energy you spend sitting at rest, or your resting or basal metabolic rate. For example, an activity with a MET value of 3 means you’re exerting 3x the energy than you would if you were sitting still. 

Activity Trackers and Fitness Apps

While not exact, your Apple Watch or Fibtit will give you a pretty good idea of how your workouts are going. "The software behind these devices combines many factors such as age, sex, weight, workout duration, and heart rate to provide a calorie burn estimate," Froerer says. "Because each wearable or app will give you a different estimated calorie burn, I would recommend finding the one you like the most and sticking with the numbers it gives you."

Workouts That Burn the Most Calories 

If you want to get the most bang for your buck, try HIIT workouts and aerobic exercise like running, rowing, and cycling—but don’t neglect strength training, either. "The more you focus on total body exercise, the more muscle recruitment you will utilize, resulting in more calories burned," Froerer says. "HIIT workouts are a quick and efficient way to burn calories and boost metabolism while continuing to burn calories throughout the day."

Remember: Calories Aren't Everything 

Remember, at the end of the day, calories are just numbers. How strong you feel is more important than losing weight. That's why Fried recommends setting performance-based goals or specific goals you can more accurately measure instead. Examples include completing a pull-up or hitting a record time on your mile. "Not only will this create a better mindset around fitness overall, but it also takes the focus off of aesthetics and won’t perpetuate the idea that exercising is merely to hit a calorie goal," she says. "It will encourage you to find joy in movement and create a sustainable routine that you can maintain and enjoy long term."