Calories burnt in exercise questions

LotusCass

So I know that MFP, activity trackers, and machines all over estimate calories burnt. To date I've been entering about 50-60% of the exercise I do. I do this as I want as accurate a measure of my daily burn on my Garmin vivofit as I can. I've just started doing fitness blender workouts and enter about midway of their calorie estimates (they give a range) as I do work to my max. I'm a 5ft 5 female 147 lbs, so maybe should enter less than halfway of their range? What FB suggests is often more than MFP though, so I'm not really sure how accurate it is.

Those of you who do FB workouts, how accurate do you find their estimates?