Every Gym with trainers should have some sort of way of calculating your bmi and body fat... Trainers use it to measure clients, train them for a month, and then measure again and show them results on paper... skin calipers are the most accurate... I have had a hand held tell me that i was 18% one time, i lowered my weight, and got 11%, then i put my weight back, and it went to 28%, then i did the calipers and measured out at 14.5, then i regripped the machine with all my stats and it read 15 %... So they can be accurate...i think getting it done first thing in the morning on an empty stomach after fasting all night should give you an accurate reading.... no supplement taken of course...