1 gram of Hb, when fully saturated in aerial blood, carries:

1 gram of pure hemoglobin (Hb) can combine with 1.39 ml of O2. However, under the normal conditions of the body, some of the Hb is in forms such as methemoglobin (metHb) which cannot combine with O2. Hence, actually 1 gm of Hb can bind 1.34 ml of O2. This is O2-binding capacity of Hb. The maximum saturation of Hb is up to 97%; when Hb is fully saturated - 1 gm carries 1.34 mL of oxygen.