What is the average weight of Brain
Weight of brain : 1300 to 1400 gms
Average brain weight of the adult male was 1336 gram;
Average brain weight of the adult female 1198 gram.

With increasing age, brain weight decreases by 2 to 3 grams.

% brain of total body weight (150 pound human) = 2%
By the time one is six years old, brain is already 90 % of the size of adult.

All of us are billionaires in terms of number of neurons in the brain
Average number of neurons in the brain : 86 billion to 100 billion
In money terms, most of us are not billionaires but in neurons in the brain, all living humans are 80 billion plus. (Its neurons and not Rupees, dollars, pounds, yen...)