Why is my Apple Watch or iPhone tracking calories burned incorrectly?

Strong records an estimate of calorie consumption using Apple Watch's in built software and Apple APIs, and we do not control the calories sent to Apple Health directly. 

How does Strong estimate calories burned?

The calories recorded come from a combination of movement, heart rate information and Apple's proprietary estimations which may be adjusted over time by Apple's internal system frameworks.

Tracking Calories on iPhone Only

If you are not using the Apple Watch to record your workouts, your iPhone provides an estimation of its own (also based on Apple's proprietary calculations), based on the movement of your iPhone during the workout.

This is very likely to provide an underestimate of calories burned as your iPhone will generally not be in motion during workouts. For accurate calorie readings, please use Strong for Apple Watch to track your workouts.

General Inaccuracies in Calories Burned

Sometimes the estimate for calories burned may not be what you expect from a full workout. There could be a few factors in this:

1. You may be looking at resting calories.The “Workout” app reports active calories burned. The “Activity” app displays both the active and resting calories burned during the workout. The total calories burned during the workout will include both the resting and active calories.
2. Apple Watch may not be in contact with your wrist.To get the most accurate heart rate measurements, make sure your Apple Watch fits snugly on top of your wrist. The heart rate sensor should stay close to your skin. Wearing Apple Watch higher up your arm (closer to your heart) may produce better results.
3. Apple Watch may be in Low Power mode, or you've enabled Workout Power Saving Mode. Turn this off in "Watch" app, under My Watch > General.
4. Your Apple Health profile may not be up to date. The calorie information generated by Apple Watch is based on your latest Weight in Apple Health. Make sure your details are up to date in the "Health" app on your iPhone. We believe that Height and Age may also factor in the calculations.
5. Strength training workouts generally burn fewer calories than you might expect.The long term benefits of weight training with regards to weight loss and calorie burning are through increased muscle mass and an associated increase in Basal Metabolic Rate, essentially meaning you burn more calories throughout the day. But during a workout, the calories burned may be less than expected.

Missing Heart Rate Data / Incomplete Workout

If you're seeing an incomplete Heart Rate read out, it's possible that the Apple Watch app crashed or closed during your workout (this could happen for a few reasons).

Unfortunately if Strong for Apple Watch crashed during a workout, this is also likely to impact the calorie total as we have no ability to 'reconnect' the separate sessions in Apple Health. In these cases, the calorie recording will represent only a portion of the overall calorie expenditure of your workout.

Please check this article to see how you can improve stability for Strong for Apple Watch.