About 10 percent
The Human brain has 75 percentage of water.
There is a wide-spread myth that humans only use 10% of their brain. While no hard percentage has been published, studies of the brain and imaging technology reveal that almost all of the human brain is being used at any given time.
If you mean "How much percentage of water does a human brain have?", the answer is about 77-78%.
A normal Human being can use its brain upto 10%. Normally of 10%, human being uses 1% to 2%. Out of these, Albert Einsteins had highest brain percentage which was 9.8%. A great miracle! Answer By- Nishant Upadhyay