exercise/calorie burn question???

Some of the exercises in here have a reputation for being generous. I don't know personally, I use a power meter on my bike which is my main thing in the summer.

The exercise database is actually based on studies and is decently accurate on many items.

The kicker is knowing if you are doing it the same intensity as that study and database entry.

Some have good intensity levels (walking, running) to know which one you are doing, some have none (elliptical) and so unknown if doing the same level as the study.

Some have accuracy problems by people logging it (Spin class was 60 min, but there was 5 min warmup and 5 min cooldown and 5 min of stretching - did you log 45 or 60 min), let alone did you do the intensity expected.

The other major kicker is MFP is an add-on system, not replace.
So it already is accounting for you to burn so many calories each day, and each min. Your BMR x 1.25 for Sedentary, x 1.4 Lightly-Active, x 1.6, x 1.75.

But exercise is added on to that already accounted for burn - but it should only be what was above and beyond it.

So if you do a low calorie burn workout for a long time (slow walk), the truly extra could be only 50% of reported.
Short and intense and big burn less of an issue.

That's where an external tracker solves the issue since they are a replace-only system - since it's reporting to MFP total daily calories burned - the math is simple and MFP corrects itself.
Workouts manually added to the tracker side (if it's not already getting them anyway) or MFP side (which sync over to tracker) are handled correctly and should be the total burned in chunk of time.

I use the database entry for Weights since there is no better estimate.
I use running & swimming calculator for my exact distance & time (pace) to replace on external exercise tracker (Garmin).
And power meter for bike which again replaces tracker.

In my experience, many of the exercise estimates are not right. I think some of them might be, but I've felt at times that they were too high or too low. I use a Polar HRM and go by what it says I burned or use an online calculator to calculate using the average heart rate my Polar tells me.

I lost most of my weight a few years ago and when I was using the MFP estimates I didn't see much success...but when I got my Polar and used that estimate I did lose weight so I've been convinced that it's more accurate.

Honestly, there is so much variability and context that impact "accuracy" that it becomes really hard to know for sure. IME, both my Garmin 935 and MFP tend to be pretty close on most standard cardio activities (biking, running). I don't track strength workouts.

Ultimately, pick one that you like the best (either because you believe it to be more accurate or because you like the simplicity of logging/tracking that way) and use that method consistently. Over time you can compare your expected progress to your actual progress and make small tweaks in how you track/log if the expected and actual are not reasonably close.

The couple of times that I have done a side by side comparison, MFP way overestimated my calories burned. I just use my FitBit now. I don't usually eat back my exercise calories anyway, so at the end of the day, it probably doesn't matter too much, but I do like to track my deficit because I'm a numbers geek.