Frequently Asked Questions
Answers to common questions about how Rep works.
Calories & Activity
How does Rep estimate calories burned during a workout?
Rep uses two sources for calorie data, in order of accuracy:
1. Your wearable (when connected)
If you have Apple Health or Google Health Connect set up and a compatible wearable, Rep reads the active calories your device recorded during the session. This is based on your heart rate, movement, and personal stats — calculated by your wearable's own algorithms, not by Rep.
Compatible devices:
- iOS: Apple Watch, Garmin, Polar, WHOOP (any device that writes to Apple Health)
- Android: Samsung Galaxy Watch, Fitbit, Garmin, Pixel Watch (any device that writes to Health Connect)
Note: Fitbit on iPhone does not sync to Apple Health (Fitbit dropped that integration in 2022), so iOS Fitbit users will see an estimate instead.
2. MET-based estimate (when no wearable data is available)
If no wearable calories are recorded, Rep calculates an estimate using the MET (Metabolic Equivalent of Task) formula — the same method used by exercise scientists and most fitness apps:
Calories = MET × Body Weight (kg) × Duration (hours)
Rep uses a MET of 3.5 for strength training sessions, which is the established value for moderate-intensity resistance exercise. Your body weight is pulled from Apple Health or Health Connect if available, or from your profile if not.
This is an estimate. Individual calorie burn varies based on fitness level, intensity, and other factors — treat it as a useful ballpark, not a precise measurement.
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