I burn more calories walking slowly, than running

[LokeAa]

According to the app statistics, I burn exactly 100 kcal per 15 minutes if I walk, and lie under zones, or by no effort if you want. A 45-minute treadmill session in which I average 80% of my maximum heart rate, I burn 240 calories, or 80 kcal per 15 minutes. Here, obviously, something is wrong with the calculation.

[JohnnyRow]

I think of heart rate as the primary measurement, and calories as secondary, derived from heart rate.  So any question about calories burned, especially comparing workouts, my first thought is look at primary data, heart rate.  That probably won't give the answer but can tell if problem is from bad heart rate readings.

[LokeAa]

@JohnnyRow , as I wrote, the walk was below zones, and that is normal, unless I walk a pretty steep hill. For the 45 min treadmill workout my average heart rate was 80% og my Max HR - also normal. Has nothing to do with bad readings. For most of my treadmill sessions, including the one I'm referring too, I also wear a pulse belt. I have not checked the last one yet, but my two previous Sense was not bad at HR. They had a delay when I ran short intervals, but that is as expected from any wrist worn device.

[charleskn]

I am not a calorie guy, though I do find calories expended to be a decent gauge of the relative effort between two similar workouts.

I am assuming that you are looking at the impact section of your session so that the calories specified are for the training session and not including part of your BMR. Do you see this with any other activities? I'd suggest taking a few screenshots to post, showing the activity, duration and calories (maybe the activities dashboard). How do the numbers compare to an online calculator, such as this one?

https://www.verywellfit.com/how-many-calories-you-burn-during-exercise-4111064