how accurate is mfp?

bfbooty

i went for a walk today not exactly sure how many miles approx 6-7 i think, i thought it would take me about an hour it took me about 1 hour 40 mins, i am, not a fast walker plenty of people zipped passed me but i was going fairly briskly for me (i have short legs lol) and i did build up a bit of a sweat (i had a buggy with me so no swinging of arms)
i logged it of course and mfp says 743 cals were burned.

i want to get a heart rate monitor thingy but money is tight right now and they're not that cheap but will get one when i can. i am just wondering though how accurate you think mfp is?

i do other workouts too most days i do aerobics and tae bo and i really work hard at it, i never eat all my cals as i just couldn't as it always says i've earned so much and i eat my full, i weigh my food fairly accurately and i have a good appetite but there's no way i could eat them all i'm often left with over 500 cals tonight over 600