The simplest method of expressing hemoglobin in SI Units is as g/L. Converting a hemoglobin g/dL to g/L involves multiplying the value by 10.
The second method of SI Unit expression is as mmol/L. The reported conversion factor from g/dL to mmol/L are:
(1) 0.6206 (Jordan; Kratz)
(2) 0.155 (Young, 1998; Wallach)
Hemoglobin is composed of 4 globin (2 alpha and 2 beta) molecules. Each globin chain carries 1 heme molecule, capable of carrying 1 molecule of oxygen. Each molecule of hemoglobin can carry 4 molecules of oxygen, so 1 mole of hemoglobin can carry 4 moles of oxygen.
Molecular weight of hemoglobin: 64, 500
Molecular weight of each globin chain: 16,100
If a molecular weight of 64,500 is used, then the conversion factor from g/dL to mmol/L is 0.155.
If a molecular weight of 16,100 is used (1 mole of globin chain, or 1 mole of oxygen carrying capacity), then the conversion factor from g/dL to mmol/L is 0.6206.
