Anna Hartz
Your smartwatch may be less accurate than you think
Smartwatches have become a normal part of everyday life for millions of people. Many wear them to count steps, track workouts, monitor sleep, and measure overall fitness. The numbers can be useful, but they should not always be taken as exact.
Calorie racking
You finish a great run feeling strong and full of energy. Then you look at your smartwatch. It says you burned fewer calories than expected and need several days to recover. That can be confusing because smartwatches do not directly measure many of the numbers they display. Instead, they estimate them using different sensors and computer algorithms, according to Videnskab.
Calorie tracking is one of the most popular features. Research shows that smartwatches can overestimate or underestimate calories burned by more than 20 percent. The difference depends on the type of activity. Strength training, cycling, and high-intensity workouts often produce larger errors. This matters because some people use these numbers to decide how much food to eat.
Step counting
Step counting is generally useful for tracking daily activity, but it is not perfect either. Smartwatches can miss around 10 percent of steps in normal conditions. Pushing a stroller, carrying heavy bags, or walking without much arm movement can reduce accuracy because most watches rely on wrist movement.
Heart rate
Heart rate measurements are usually reliable when you are resting or exercising at a low intensity. Accuracy often drops during harder workouts. Sweat, skin tone, arm movement, and how tightly the watch fits can all affect the results.
Sleep tracking
Sleep tracking also has limits. Most smartwatches can usually tell whether you are asleep or awake. However, they are much less accurate when estimating stages such as deep sleep and REM sleep. That means your sleep score may not fully reflect how well you actually slept.
Recovery and VO₂
Recovery scores and VO₂ max estimates also rely on calculations rather than direct measurements. These figures can be useful for spotting long-term trends, but they are not perfect.
Experts say smartwatch data should be treated as a guide instead of an exact measurement. It is also important to pay attention to how you feel, how well you perform during exercise, and how quickly your body recovers. Those signals often give a better picture of your health than the numbers on your wrist.
