# Tracker accuracy > Trackers give rough guides, not exact figures. Step counts can be off in either direction, wrist heart rate is the most dependable measure, and calorie estimates are the weakest. Use them to watch your own pattern over weeks, and go by how your body feels. - Type: Guide - Topic: Technology & Tools › Wearables & Health Data - Reviewed by: Andrew Schox, BSc(Hons) PGradDipPod MPod, Podiatrist (2026-10-21) - URL: https://twikka.com/learn/tracker-accuracy - Updated: 2026-10-21 - **Step counts are a rough guide, not an exact score.** Wearables mostly undercount, but some overcount [1]. - **Wrist heart rate is the most dependable measure,** though single readings can be off, especially during weights or cycling. - **Calorie figures are the weakest,** so don't use them to decide how much to eat. - **Your own pattern over weeks is more useful** than any single number. ## How accurate are step counts on phones and wearables? Step counts are a rough estimate, not an exact figure. Wearables mostly undercount steps, with errors from about −9% to 12% [1]. Some overcount instead, including for older adults, so the direction of error isn't consistent [2][3]. The brand and model matter a lot. Some models count steps closely, while others can be far off [2]. Your walking speed matters too: trackers underestimate steps during slow walking, by anywhere from 0.94% to 60% [4]. Differences from a hand count ranged from 0.0 to 26.4%, depending on the tracker and the walking speed [5]. What to do with this: - **Treat your step count as a rough guide** rather than an exact score. - **Don't compare totals between two different devices.** This is why your phone and your watch can show different numbers. - **If you walk slowly, expect your tracker to miss some steps.** - **Judge progress from how your own days compare** on the same device, not from any single number. > **Try this:** For one week, note your step total at the same time each day on one device. Look at whether the days are trending up, rather than at any one figure. ## How accurate are heart rate, activity minutes and calories on a wearable? Wrist heart rate is the most dependable of the three, though individual readings can be off. Calorie estimates are the weakest, and activity minutes are best treated as rough too. **Heart rate.** Wrist-worn heart rate typically shows an error of about ±3%. How close it gets depends on the person, how hard they're working and the device model [1]. Readings stay close to the reference during sleep, at rest and on a treadmill from walking to running, differing by roughly half a beat a minute or less on average. The gap is larger during resistance training (7.26 beats a minute lower on average) and cycling (4.55 lower) [6]. Even when the average error is small, single readings can be far off [7]. Movement, moisture and poor skin contact can disturb the signal [8]. Wrist heart rate may also be misestimated more in people with heart disease, so people with a heart condition shouldn't rely on a watch reading [8]. **Calories.** No tested device proved accurate. The error was above 30% for all brands [9], and fewer than 10% of estimates fell within acceptable limits in controlled settings [10]. Wearables tend to underestimate, by about 3 kcal per minute on average [1]. Over a whole day, all devices underestimated total energy use, by 475 to 898 kcal, which makes them of little use for balancing what you eat with what you use [11]. **What to do with this:** - **Don't use a watch's calorie figure** to decide how much to eat or to judge a session. Treat it as a very rough guess. - **Check how hard the activity feels** as well as the number on the watch. - **Expect heart rate to read less well** during weights or cycling, or if the watch is loose or the skin is wet. - **Look at your own pattern over weeks** rather than any single reading. ## When to check with a health professional If you're starting exercise after a long break, it's always a good idea to see your doctor first. For an injury or a health condition, see a health professional, such as your doctor or a physio. Most accuracy studies were in healthy adults, so tracker numbers aren't medical information [1][7][8]. Go by how your body feels rather than the watch. Blood oxygen readings have limited accuracy when oxygen levels are low, and a normal-looking reading doesn't mean symptoms can be ignored. Call your local emergency number for chest pain or pressure (or pain spreading to the arm, neck, jaw or back, especially with sweating or feeling sick), severe breathlessness, fainting or collapse, signs of a stroke, a serious injury, or someone who isn't safe. For a sore muscle or joint, ease off and get advice if it persists. ## Quick answers ### Why do my phone and my watch show different step counts? Brands and models can differ a lot, so two devices will often disagree, and neither is exact. Where you carry or wear a device can matter too. Don't compare totals between devices. Pick one and judge progress from how your own days compare on it. ### Is a tracker worth using if it isn't exact? Yes, as a rough guide. The numbers aren't precise, but your own pattern over weeks on the same device can show whether you're doing more. Judge progress from how your days compare with each other, not from any single number. ### Should I use my watch's heart rate to decide how hard to exercise? Use it as a rough guide only. Check how hard the activity feels as well as the number on the watch. Heart rate tends to read less well during weights or cycling, or if the watch is loose or your skin is wet. Look at your pattern over weeks. ## Sources 1. Doherty C et al. (2024). Keeping Pace with Wearables: A Living Umbrella Review of Systematic Reviews Evaluating the Accuracy of Consumer Wearable Technologies in Health Measurement. Sports Medicine. https://doi.org/10.1007/s40279-024-02077-2 2. Abdul Jabbar K et al. (2023). Physical Activity in Community-Dwelling Older Adults: Which Real-World Accelerometry Measures Are Robust? A Systematic Review. Sensors. https://doi.org/10.3390/s23177615 3. Straiton N et al. (2018). The validity and reliability of consumer-grade activity trackers in older, community-dwelling adults: A systematic review. Maturitas. https://doi.org/10.1016/j.maturitas.2018.03.016 4. Van Remoortel H et al. (2012). Validity of activity monitors in health and chronic disease: a systematic review. International Journal of Behavioral Nutrition and Physical Activity. https://doi.org/10.1186/1479-5868-9-84 5. Fokkema T et al. (2017). Reliability and Validity of Ten Consumer Activity Trackers Depend on Walking Speed. Medicine and Science in Sports and Exercise. https://doi.org/10.1249/mss.0000000000001146 6. Zhang Y et al. (2020). Validity of Wrist-Worn photoplethysmography devices to measure heart rate: A systematic review and meta-analysis. Journal of Sports Sciences. https://doi.org/10.1080/02640414.2020.1767348 7. O'Driscoll R et al. (2020). How well do activity monitors estimate energy expenditure? A systematic review and meta-analysis of the validity of current technologies. British Journal of Sports Medicine. https://doi.org/10.1136/bjsports-2018-099643 8. Lambe R et al. (2026). The accuracy of Apple Watch measurements: a living systematic review and meta-analysis. NPJ Digital Medicine. https://doi.org/10.1038/s41746-025-02238-1 9. Germini F et al. (2022). Accuracy and Acceptability of Wrist-Wearable Activity-Tracking Devices: Systematic Review of the Literature. Journal of Medical Internet Research. https://doi.org/10.2196/30791 10. Fuller D et al. (2020). Reliability and Validity of Commercially Available Wearable Devices for Measuring Steps, Energy Expenditure, and Heart Rate: Systematic Review. JMIR mHealth and uHealth. https://doi.org/10.2196/18694 11. Ferguson T et al. (2015). The validity of consumer-level, activity monitors in healthy adults worn in free-living conditions: a cross-sectional study. International Journal of Behavioral Nutrition and Physical Activity. https://doi.org/10.1186/s12966-015-0201-9 --- Source: Twikka (https://twikka.com/learn/tracker-accuracy). General information about physical activity, not medical advice.