how much blood on average does the human body have
The amount of blood in a human body varies, of course, with the size of that body. Over the range of sizes we usually encounter for average people, this is approximately 7% of body weight. And the density of whole blood, again on average, is about 1.06 grams/ml. So, for example, if a person weighs 185 lbs, in kilograms this converts to about 84 kg body size. Taking 7% of this gives 5.87 kg of blood.