Under normal circumstances, the average capacity of an adult bladder, both male and female, is between 400 and 600 milliliters, or between 13 and 20 ounces, according to WebMD. Other sources give an upper limit as high as 1,000 milliliters, or nearly 34 ounces.
The bladder is a muscular pouch that sits just behind and above the pubic bone. When it is empty, it is about the size of a pear. The wall of the bladder is flexible to allow distension when filled with urine. Bladder capacity is difficult to gauge because the correlation between bladder fullness and the urge to urinate is different for every individual.