Active calories is just out of control?

I'm not sure what it could be. Mine seems to be working fine. I walked 7394 steps today and some of that was working outside. My calorie count is 206. I have only had this watch for a few weeks, but so far I really like it. I had an Apple watch for two years and a Fitbit before that. I don't think any of them are perfect as far as calorie count. I wear the watch all the time. As far as cycling and hiking it seems like a much better fit for me.

I have experienced the same problems and not found a solution so far:

https://forums.garmin.com/forum/on-the-trail/wrist-worn/fenix-5x/1228396-calories-too-high

I do not think it is a Fenix 5X problem, since other people experience the same issues with different devices. Garmin Support has not responded so far...

You may want to check what your heart rate is during this. If the watch is overcounting your heart rate (eg. due to excess movement of the watch on your wrist) then it may lead to an overestimate of calories burned.

Most of the times it's an issue related to bad configuration (user profile), other times it's a problem related to HR spikes (bad readings from the OHR or from the HRMs in case of low battery). I had a discussion with the DEVs about the energy formula and we concured it's a sort of religious thing where each has their own values.

At that point in time I was burning 500+ Cal in 45' of Aquagym and it did seem a lot. About 700 for a TacX 1 hour session in Z2 threshold which seemed a lot too and this is why I reported it.
ST3 analyzed the latter and took off 80 Cal so all in all it's not such an excessive consumption.

However, 2 betas have been released so far and now the values for the same activities have considerably dropped (580 for TacX and 350 for Aquagym). I can't say whether it's because I'm getting fitter or because they actually touched the equation. I suggest you try with the latest Beta and see if calories still seem offset.

Today I really had a lazy day with not much movement at all. Altogether I had 3600 steps and burned 296 calories. Indeed, I had some spikes, but these are true spikes, due to getting laundry from the washing machine (two floors) and shopping. But I was rarely above 100 bpm.

My user profile is set up correctly. At least to my knowledge.

I really believe it is heart rate readings. Actually...I believe it is the algorithm Garmin uses for high HR readings. An occasion high spike should NOT cause extreme activity calorie numbers like it appears to be doing for many since the Fenix 3 HR. Since there are so many reported issues like this with any of the Garmin Fenix HR versions I wish they would have more options than Wrist monitor on/off. Why not have the option to take periodic readings rather than any time you move your wrist? The fact is...I am typing now and I bet this unit somehow read my heart rate at 130 plus since wrist HR monitors tend to have below average accuracy. Have an option to start reading if there is movement for 10 seconds or more. Something other than constant on when your wrist moves. If I disable HR it calms way down, but then it is just off. Why is the Apple Watch much more accurate at this then Garmin? I have read so many posts about this issue recently and most will have a few in there saying they have contacted Garmin but they just ignore it..
As for the profile configuration...I assure you it is right on. I went through and checked every small thing. Then I went through and did it again. I also compared watch to connect to website to make sure something wasn't over riding the other. This is just poor wrist HR combined with always on with any movement.
On a side note...I am not saying that only Garmin has poor wrist HR. All of the products out there that have this are not very accurate. If you have a darker toned skin, tattoo etc it makes it worse. Then you also need to have it fairly tight. Even with all of that....still not very accurate at all.

*I have also tried using % of heart rate reserve, HR and the others that were options. I have made sure my resting HR was accurate.
*The step counter is actually pretty accurate. I do wonder how taking 30 steps can mean 40 calories burnt though. This is just crazy stuff that could easily be fixed if Garmin cared.

I never look at my calories burnt outside of an activity but at the risk of asking the obvious - Your weight isn't set to something ridiculous is it?

Yesterday I had a hydrobike session with much stronger muscular fatigue than heart fatigue. The 459 Cal seemed appropriate.
Upon loading the log into ST3 I saw the Cal were not retouched by its algorithm so ... maybe it's ALSO a matter of version (you and I might not have the same equation running in the watch).
<-- 4.16b here.

Yesterday I had a hydrobike session with much stronger muscular fatigue than heart fatigue. The 459 Cal seemed appropriate.
Upon loading the log into ST3 I saw the Cal were not retouched by its algorithm so ... maybe it's ALSO a matter of version (you and I might not have the same equation running in the watch).
<-- 4.16b here.

You're confusing activity calories with non-activity calories. What's being discussed here is the latter not the former. They're not calculated or presented in the same way. We're trying to figure out how Garmin justifies so many calories for so little activity, beyond the BRM*1.2 that's given as "resting" calories, and what we already get from doing actual timed activities (run, ride, swim, etc).

I can run 10k with an average HR of 145bpm and get 500 activity calories and this seems about right. But if i walk 10k across a day (rest day, run day, doesn't seem to matter) with a HR range of 60-100bpm and average ~75bpm i'll get 800-1200 "active" calories. My HR trace looks fine, my profile is set up correctly, weight height etc all ok, activity level, HR zones, VO2max makes sense, and so on. It's all fine.

Just that Garmin gives 1.5-2x the calories for an equivalent distance that has a much lower heart rate.

In particular this screws up the daily targets in myfitnesspal. And for those of us who try and stick to a calorie goal there (for weight loss or maintenance, racing weight, or just general health) it's really bad. Requires constant micromanaging at best; at worst you end up overeating.