Each gram of Hb can combine with 1.34 ml of oxygen. Normally, blood contains » 15g Hb/100ml of blood [or
150g/L]. Hence the oxygen carrying capacity of Hb is 15 X 1.34 = 20 ml oxygen/100 ml blood.
The amount of oxygen in the blood (sum of both forms, dissolved and bound to hemoglobin) is called the oxygen
content of blood and is described in ml O2 per 100 ml blood (or volume %).
The O2 content of arterial blood (CaO2) is » 20 vol% ; the O2 content of venous blood (CvO2) » 15 vol%.
Therefore, each time blood circulates through the circulation, 5 vol% of oxygen is taken up by the tissues