Total Iron-Binding Capacity Calculator

How it is calculated

The tool needs two lab values: serum transferrin in mg/dL and serum iron in µg/dL. It estimates total iron-binding capacity as TIBC = 1.389 × transferrin in µg/dL, a factor that reflects two iron-binding sites per transferrin molecule. Then UIBC = TIBC − serum iron is the binding capacity not yet used, and transferrin saturation = serum iron ÷ TIBC × 100 is the share of capacity that is filled. TIBC and UIBC print with two decimals. Transferrin must be above 0 and serum iron cannot be negative; 0 is accepted. Serum iron larger than the calculated TIBC is physically impossible, so the tool shows no result instead of a saturation above 100 %. TIBC itself cannot be typed in directly.

Common mistakes

• Entering transferrin in g/L. The field is mg/dL, so a value of 2.5 g/L must be typed as 250; typed as 2.5, the calculated TIBC is only about 3.5 µg/dL and any normal serum iron is then above it, so no result appears.
• Typing a measured TIBC into the transferrin box. This tool multiplies the number by 1.389 again, so give it transferrin only.
• Entering serum iron in µmol/L. The field expects µg/dL, and the same blood sample gives very different numbers in the two units.
• Reading a missing result as a glitch. When serum iron is higher than the capacity implied by the transferrin you entered, the combination cannot be real and usually signals a unit or digit error.
• Using the calculated TIBC as if it were directly measured. It is an estimate from transferrin, and labs that measure TIBC directly may report a slightly different value.