How much water is really needed for Hydration?

I have read 80oz, 50 oz and 40oz. My brother says 64 oz.    I am able to get in 64 oz a day. After that I can not do anymore.  Outside activities I am getting way more but I want to know in general.

I have always been told that the ideal is 8, 8oz glasses of water a day which is 64oz. If your NUT says more I would go with their advise, if not I would say you are doing good at 64oz. a day.

I take what my Nut says as a grain of salt.  Nothing she has told me has been right.  

i take 2 litre of water per day and i have no problems getting it down

I get about 100 oz of fluid, because I run and workout a desent amout. 

My guideline is six to eight 8 oz glasses - but I'm also told to keep ahead of thirst, because if I feel dry/thirsty, get constipated, or if urine is a concentrated color, I need more water.  I usually get in up to about 64 oz., sometimes more, sometimes less, and neither constipation or urine have been a problem for me.

My doctor says 64 oz as well. I have a hard time getting that in. I never thought I'd have to force myself to drink.

64-75 oz for me not including FF milk, vino.  I try to get all fluids in b4 6pm. 

64oz is good, remember we ge****er from other foods and beverages besides just drinking water so if you are getting 64 of jus****er that should be plenty.

My PCP and NUT told me 64 ounces was sufficient. I have no problem getting that in. That's not counting the water in coffee, protein drinks, jello and my favorite S/F popsicles.