Is Apple Watch calorie burn accurate?

Not very, for calories. Across 56 studies, the Apple Watch’s calorie estimate was off by about 28% on average. Its heart rate was off by about 4% and its steps by about 8%. So trust it for heart rate and steps, use its calories to compare one day with another, and don’t eat them back as if they were exact.

The watch shows calories with the same confidence as your heart rate, to the single calorie. But a watch has no way to measure the energy you burn. It has to estimate it from what it does measure, like your heart rate and your movement, and every step of that estimate adds error.

The simple version

The watch is a good pedometer and a good heart monitor that also makes an educated guess about calories. Use the first two as facts and the third as a hint.

The studies

• The 2025 review. It pooled 56 studies with 270 comparisons against lab measures. Every group of calorie results was off by more than 10%, the authors’ line for a valid measure. No group of heart rate results crossed it.
• A 2017 test of 7 wrist devices on 60 people, while sitting, walking, running and cycling. The Apple Watch had the lowest error of the group. Still, no device got its calorie error under 20%.

What to do

• Use the watch’s daily steps to pick your activity level on the calories from your steps calculator.
• Compare calories day to day on the same watch, but don’t add its exercise calories to your food budget. See should you eat back your exercise calories?
• Let your scale settle it: four weeks of weigh-ins against your meals on the real TDEE calculator show what you really burn.