How Accurate Are Calorie Counts on Cardio Machines?

person running on a treadmill

Getty Images / Ziga Plahutar

Calorie counters on treadmills, ellipticals, and other cardio machines are convenient and may provide you with useful information that helps keep you motivated to exercise. However, these calculated calories are just rough estimates.

While some types of cardio machines are more accurate than others, none of them will be 100% accurate. In general, they overestimate your calorie burn by about 100 calories per 30 minutes of moderate exercise because they can't account for all the factors involved in calorie-burning.

The good news is that there are ways that you can better understand your unique estimated calorie burn.

Personal Calorie Burn Factors

Many cardio machines ask you to enter your personal details, like your gender, age, and weight before you begin. In some cases, they have wearable or touch sensor heart rate monitors that you can use.

In general, cardio machines, such as treadmills, use standard formulas to figure out the number of calories burned. It is similar to a calorie-burn formula that you can calculate on your own.

However, when it comes to figuring out calories burned, there are other important factors to consider.

  • Fitness level: Whether you're just starting a general exercise program or switching activities, the newer you are to it, the more calories you will burn. As you become more fit, you will burn fewer calories doing the same activity for the same period of time.
  • Body composition: When you start exercising, you may have more fat than muscle mass, so you will burn fewer calories at first. As you build muscle, your body becomes more efficient and will burn more calories for the same amount of exercise.
  • Body size: When two people weigh the same, the one with a larger frame tends to burn more calories.
  • Age: Older individuals tend to burn less calories than individuals who are younger. This may be linked to muscle mass loss, metabolic changes, as well as health conditions.

For example, if a 160-pound assigned female with 35% body fat and a 160-pound assigned female with 20% body fat are both running at a 10-minute mile pace, the treadmill will display the same amount of calories burned. However, the second individual, who has lower body fat and more muscle mass, is actually burning more calories.

Experience and Efficiency

More than with other machines, when you run on a treadmill, your form and efficiency play a larger role in calorie burn. New runners usually burn more calories than more experienced runners, even at the same pace and distance. This is because beginners tend to be inefficient, running with a side-to-side movement and lots of bouncing up and down. These extra motions expend more energy than the experienced runner's efficient stride.

Also, if you are using the handrail on a treadmill or stair-stepper, you may be diminishing your calorie burn because you're making the workout easier. You won't be swinging your arms naturally with your stride.

Due to the way athletes use them, there are also variables in the accuracy of different types of machines. For example, a stationary bike limits movement so most individuals use it in generally the same way. The calorie counters on these tend to be more accurate than treadmills and stair steppers, which offer more freedom of movement. 

Cardio Machine Formulas

The formulas that cardio machines use to calculate can vary from one manufacturer to another. Generally, most machines will base their formula on The Compendium of Physical Activities, which assigns a value to a variety of activities, from exercise to inactivity. The values are based on the Metabolic Equivalent, known as MET.

For instance, the running category is filled with variables. It states that jogging burns 7.0 MET (7.0 kcal/kg/hour), running 6 miles per hour (a 10-minute mile) burns 9.8 MET, and running 10 miles per hour (a 6-minute mile) burns 14.5 MET. This does not account for any factors relating to you personally.

One MET unit is equal to 1 kcal (kilogram calorie) per kilogram per hour, essentially the amount of energy expended when quietly sitting. The amount of energy (calories) you burn for other activities is compared with this one-MET baseline.

How to Accurately Measure Calorie Burn During a Workout

Unless you go to a lab and your oxygen, heart rate, as well as other measurements are taken, there isn't an exact way to measure calorie burn during a workout. It's best to utilize multiple tools to give you the best calorie burn estimate possible.

Wearable Fitness Trackers

These wearable devices can monitor and track all sorts of health information, such as heart rate, activity level, and personal goals. Research notes that wearable fitness trackers are associated with motivation and accountability when it comes to health and wellness.

While the heart rate monitor tends to be reliable on a broad variety of wearable fitness trackers, when it comes to measuring calorie burn, research notes that they tend to be inaccurate. Specifically, the most accurate wearable fitness tracker was off by an average of 27% and the least accurate by 93%.

With that said, these shouldn't be solely relied on for measuring calorie burn, but they can still be a beneficial part of tracking your overall health.

Rating of Perceived Exertion Scale

You can gauge your workout by using a Rating of Perceived Exertion (RPE), which is a subjective scale that describes how hard an individual believes they are working out. Based on factors, such as muscle fatigue and sweating, you can rate the intensity of your workout on a scale ranging from 6 to 20.

Research notes that you'll tend to burn the most calories working out at a difficult intensity level (rating of 14 or above).

To figure out your estimated heart rate, multiply your RPE by 10. This can help you understand the intensity level of your workout, so you can have a better sense of calorie burn.

Target Heart Rate

In general, higher intensity workouts burn more calories. This means your target heart rate range should be between 77% and 93% of your maximum heart rate, which will vary based on age.

Because heart rate is associated with how hard you're working, wearing a heart rate monitor can be helpful when determining calories burned. In some cases, the heart rate monitor will have a calorie burn estimator. When associated with your heart rate, these tend to be more accurate.

Having a general idea of how many calories you're burning during exercise is a good way to manage your health. Just keep in mind that many calorie counters are overestimating what you're actually burning. Remember that how you feel after the workout and your overall health are more important than the exact number of calories you're burning.

11 Sources
Verywell Fit uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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By Christine Luff, ACE-CPT
Christine Many Luff is a personal trainer, fitness nutrition specialist, and Road Runners Club of America Certified Coach.