Calorie count way out on forerunner 235 since I connected MyZone HR monitor

BTW, the screenshot from MyZone with the Move Summary refers to the time of 1hr 31min, while Garmin to only 40 minutes! So in fact your MyZone report gives you the calories burned already during one hour before you started to run at all, it means it likely already contains an extra hour of RMR (Resting Metabolic Rate), and that would already account for a big difference in reported Calories expenditure.

Yes I was wearing the strap for longer, but look at the difference... 80 calories compared to 670, it doesn't account for that. I can show you another example where the strap was on for a similar duration to the watch, it happens every time. 

It's clear that I didn't run nearly 5 miles at an 8 mile pace and only burn 80 calories.

Ah yes. According to my watch, my resting HR on Tuesday was 32.

The weight entered into Garmin was 164 lbs, which is 74.4 kg. This was two years ago so I was 28. 

This was two years ago so I was 28. 

The activity you shared, tells the date 2020/05/12, is that wrong then?

Well, using the data you gave, and an algorithm from Quora, it gives 295 Calories, but this algorithm does take in account the Resting HR, and also not the HR Zones. From that point of view it looks like both the MyZone and Garmin are way off, each in the other direction.

Garmin takes in consideration also the average resting HR, and likely also the time spent in individual HR zones. Seing you've spent most of the time in the green Zone 3, it may be perhaps the reason of the undercalculation. Perhaps you need to adjust the HR Zones to better respect your physiology.

Another possibility is, that although the graph in the GC account shows the HR curve from the HRM chestbelt, it continues using the internal wrist HRM for the Calories calculation, and using hence possibly quite different HR values. To see if it is the case, disable the internal HRM entirely for the next run.

• It’s definitely an issue that Garmin needs to look at because I already contacted MyZone and they have confirmed the HR readings are passed correctly to Garmin, and you can see that is the case on the Garmin devices, however how they then calculate calories is the mystery. My watch has no hr reader so only source to get hr is myzone belt so it can’t be getting confused by any other readings. Frustrating because it was fine when I had a Garmin belt, which packed up after 2 years but now won’t calculate with the myzone belt

Can you post the screenshots of the following pages from your GC Web account? 

• https://connect.garmin.com/modern/report/13/all/last_seven_days
• https://connect.garmin.com/modern/report/3/all/last_seven_days
• https://connect.garmin.com/modern/report/41/wellness/last_seven_days
• https://connect.garmin.com/modern/report/60/wellness/last_seven_days

Thank you, I will disable the internal HRM. I didn't know I could do that.