Calories burnt on MFP....are they accurate?

They are only a very general estimate. Because after all, how do they know how intense of a workout you put in? For myself they're usually right-on or a little low compared to the readings I get on my heart rate monitor. But I'm sure a million people will chime in and say they are high (or low). A HRM can be a useful tool but it too is an estimate (probably more accurate than MFP though). I would just enter in the calories and use trial-and-error to adjust from there. Not losing the expected amount of weight? Then cut down on the projected MFP calories until you find where you want to be. Simple.

I agree, it WAY overestimates mine. I had the bodybugg a while ago and found that my at-home elliptical machine was very accurate (surprisingly!). My bodybugg would show I burned only 50 calories less on a 45 minute workout than the elliptical machine guesstimated (and this was pretty consistent. it was almost always 40-60 calories different! I was shocked!). I no longer use the bodybugg, so now I just take whatever the elliptical says. My elliptical will report I've burned about 400 calories, and MFP will show I burned 778. That's a pretty big difference!

I find them somewhat accurate for some activities but wildly inaccurate for others.

I generally assume that I am burning about 10 calories per minute for most forms of intense exercise. I find that mFP has some wildly inaccurate numbers if we use that as a baseline. It seems spot-on for jogging and cycling and calisthenics, but I can't understand why it thinks shoveling snow for 45 minutes would have the same caloric expenditure as running for 45 minutes. I keep picturing some sort of snow shoveling superhuman who is a lot faster than I am at 6am when I've just awakened.

It also does not have enough fine-grained exercise options at times. I take Brazilian Jiujitsu and mfp seems to assume that every minute I take is sparring because there's only one BJJ activity and it is ridiculously high calories per minute. Sparring is certainly extremely intense (likely > 10 cal/min) but that's like 1/3 of the class. There's also technique drills which are barely more exertion than a casual walk.

I try to fudge the numbers to make up for mfp's inaccuracies as best I can. For a 1.5 hour class of BJJ I record 45 minutes and that seems to have roughly the correct calorie expenditure.

MFP tends to overestimate...it assumes you are work at a very high heart rate. they only time it's close to my HRM is for spinning. can't get close on the elliptical trainer.

I aksed the same question recently, because I can't believe that 80 mins brisk walking could earn me over 500 calories!

I'll be getting a HRM eventually, but right now take it with a big grain of salt

Depends on the person I guess. I typically burn 300 for a 30 min walk. But I'm big and I walk fast.

I've found that walking has been pretty close for me. I checked several sites and they were all within 10 - 20 calories of MFP.

I just started at a gym this week too! The trainer I met with said I need to eat more when I exercise, but not as much as MFP says to eat when I add exercise.