A 60 kg man has haematocrit of 40%. His plasma volume would be approximately:

Plasma volume = Total blood volume * (1 - Hematocrit) The total blood volume is about 8% of body weight Blood volume of 60 kg man = 0.08 * 60 = 4.8 L Plasma volume = total blood volume * (1-hematocrit) = 4.8 * (1-0.40) = 4.8 * 0.60 = 2.88 L Also, about 60% of the blood is plasma and 40% is RBCs Thus, plasma = 5% of body weight and haematocrit is 3% of body weight