Fenix 6 Pro, wrong calculation of burnt calories for cardio activity.

Hi, for the past 2 weeks I figured out that sometimes the calories burnt during an activity is calculated incorrectly.

For example, if I do an activity for 60 mins with an average heart rate of 146 bpm heart rate, i would expect around 800 cals to be burnt.

But my watch says 380-400 cals. How can I double check if there is an issue? Strangely, this happens a few times a week. Not on every activity.

The activity type is "cardio".

I use a chest strap for heart rate measuring

I'm using the latest firmware 15.20

Thank you

0 LisaSpearz over 4 years ago

I am having this same issue

0 LisaSpearz over 4 years ago

I’m 180 pounds. I just ran for 40 minutes on the elliptical and my watch says I only burnt 195 calories. I’m wearing a 12lb weight vest on top of my own weight. This watch is brand new. I need to know what’s causing this. I think something I installed from Garmin IQ might be causing it.

0 OnurSenturk over 4 years ago in reply to LisaSpearz

I got my watch replaced and it is working fine now.

One thing that might help you would be to get a chest strap.

If you are not using your watch tight enough, it might not be reading you heart rate accurately.

What is the average heart rate for the activity for you?

0 mcalista over 4 years ago

800 calories in 60 minutes is a lot, but definitely feasible. But unless you have an unusually low maxHR, burning this many calories at 146 bpm seems unlikely.

What are you basing your expectation of 800 calories on?

0 LisaSpearz over 4 years ago in reply to OnurSenturk

My heart rate running should be super high. Not 95-105. I’m 180lbs, and wearing a 12lb weight vest. I ran for 40 minutes. My heart rate should max out over 150. This isn’t working right. 195 calories for 40 minutes is a joke.

0 LisaSpearz over 4 years ago in reply to OnurSenturk

I’m not wearing a chest strap. My watch is tight. It worked when I got it last month. It doesn’t work now/

0 mcalista over 4 years ago in reply to LisaSpearz

The calculation seems right for 95-105.

It's the HR data that's wrong for that kind of effort. A common issue when running is for the band to be too loose, and external light can enter the HR sensor.

Another possibility with the ellipitcal is wrist flexing while grabbing the handles, which can also make it hard for the sensor to get an accurate reading. (this can also be the case with other "gripping" activities like strength training or hiking poles. Try positioning the band higher on the arm and further away from the wrist bone

0 LisaSpearz over 4 years ago in reply to mcalista

My elliptical is hands free. It’s just the feet part and it’s set at a mid resistance so It requires more effort for my legs to rotate the pedals. I keep balance without using anything to grip. I am holding my phone. Even without it in my hand, I don’t think it’s going to change things. My watch is so tight that it leaves marks and sometimes irritates my skin.

0 7017726 over 4 years ago in reply to LisaSpearz

You should be burning around 110-120 calories per mile run, if run at level.

0 7017726 over 4 years ago in reply to mcalista

All depends on a person's weight, of course. At 180 pounds (OP didn't give his weight), a fairly intense workout for a fit person (not 'athlete'), should burn around 600-700 calories an hour. For the OP to expect to burn 800 calories, he needs to working very hard. His average HR was 146, which is fairly high, so maybe he was. The best guide is mileage. At 120 lbs, I burn about 70 calories per mile (which is remarkably uniform with regard to speed). OP needs to tell us how many miles he ran and what his weight is. Then we can advise whether there is a possible problem with his watch.