Fitness Band Calorie Counter Accuracy Tests

Fitbit Flex Activity Data on App
Fitbit Flex Activity Data on App. Bruce Gifford/Moment Mobile/Getty Images

Fitness trackers are all the rage. Before you rely on a new device, it's worth taking the time to research what you're getting. Certain products claim to accurately count calories and monitor all forms of movement throughout the day. But can they live up to the hype?

Understanding the strengths and limitations of today's fitness trackers can help you decide whether or not to base your health goals around the data they provide.

What Does the Research Say?

Several independent studies have shed light on the reliability of fitness trackers. According to a study at Ball State University, even some of the most well-known devices miss the mark.

In this study, thirty healthy adults between the ages of 18 and 80 wore five different physical activity monitors and one portable metabolic analyzer. These included the:

  • Fitbit One
  • Fitbit Zip
  • Fitbit Flex
  • Jawbone UP24
  • Omron HJ-720IT

The metabolic analyzer used was the COSMED K4b2, an Italian product that reliably measures energy expenditure based on oxygen consumption.

Subjects participated in various exercises, ranging in intensity from lying down to completing household chores to running and stair climbing. The researchers compared the activity measurements from the fitness monitors with those of the gold-standard COSMED to see how close they came.

The answer: not very. Although resting measurements were accurate, other forms of activity were not. Energy expenditure was overestimated by 16% to 40% during exercise (excluding cycling).

On the other hand, most of the monitors underestimated calories burned through household activities by as much as 34% (except for the Fitbit Flex), though wrist monitors were more reliable than those worn on the hip. For counting steps, the monitors were generally accurate for structured exercise (except cycling), but undercounts ranged between 35% and 64% for steps.

The Ball State researchers concluded that activity trackers aren't accurate enough to reliably determine calories burned.

Another study from 2019 compared two wrist trackers, the Fitbit Charge 2 and the Garmin vivosmart HR+. Twenty participants over age 65 were monitored for 24 hours. Results were compared against validated technology, the ActiGraph and New-Lifestyles NL-2000i.

The Fitbit was shown to overcount steps by 12%, and it underestimated daily calories burned. Conversely, the Garmin undercounted steps by 9%, and it was even less accurate than the Fitbit at calculating overall energy expenditure.

Nonetheless, these results are more promising than the Ball State trial. The authors concluded that fitness devices are good enough for personal use but cannot be relied on in research or clinical settings.

How to Measure Your Progress

There's a saying that goes, "what gets measured gets managed." Accountability is an essential component of goal setting. Although you may not want to put all your faith in a fitness tracker, simple steps like keeping a food diary or adding your workouts to your calendar can help you stay on track.

Set small goals along your health journey to continue making progress. What can you do differently this week to get closer to your ultimate goals? Getting in shape doesn't have to be an expensive proposition. Drinking more water, walking every day, or even just getting to bed earlier can go a long way towards improving your health.

A Word From Verywell

Sometimes the fitness industry overcomplicates getting in shape. While fitness trackers may serve as a fun reminder to move more, the information they provide should be taken with a grain of salt. Whether you use an expensive device, a free app, a pen and paper, or even a workout buddy for accountability, you can achieve your fitness goals as long as you make long-term changes a priority.

2 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.
  1. Nelson MB, Kaminsky LA, Dickin DC, Montoye AH. Validity of consumer-based physical activity monitors for specific activity types. Med Sci Sports Exerc. 2016;48(8):1619-28. doi:10.1249/MSS.0000000000000933

  2. Tedesco S, Sica M, Ancillao A, Timmons S, Barton J, O'Flynn B. Validity evaluation of the Fitbit Charge2 and the Garmin vivosmart HR+ in free-living environments in an older adult cohort. JMIR Mhealth Uhealth. 2019;7(6):e13084. doi:10.2196/13084

By Wendy Bumgardner
Wendy Bumgardner is a freelance writer covering walking and other health and fitness topics and has competed in more than 1,000 walking events.