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Iron Binding Saturation Relationships

Compare direct TIBC saturation and the transferrin-based approximation.

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Calculator inputs

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How to use this calculator

  1. Enter the known values in the units shown. Results update as you type.
  2. Where results are editable, change one to solve backwards. Lock a value to hold it fixed.
  3. Use the worked example to check the method. Reset restores the starting fields.

Use the result with context

Health results are educational estimates, not a diagnosis or treatment recommendation. A qualified clinician can interpret measurements in the context of your health.

Formula and method

Iron 100 µg/dL and TIBC 400 µg/dL give 25% direct saturation. Separately, iron 100 µg/dL and transferrin 250 mg/dL give a 28.36% transferrin-based estimate.

TIBC saturation (%) = 100 × iron/TIBC; transferrin estimate (%) = 70.9 × iron(µg/dL)/transferrin(mg/dL).

Worked example

Enter these known values and leave the other values blank.

Serum iron concentration (Fe)
100 µg/dL
Total iron-binding capacity (TIBC)
400 µg/dL
Serum iron concentration (Fe)
100 µg/dL
Serum transferrin concentration (TF)
250 mg/dL
Transferrin saturation (TSAT)
25 %
Transferrin-based saturation estimate (%)
28.36 %

Assumptions and limitations

  • The direct TIBC ratio and transferrin estimate are separate models. The 70.9 factor uses a conventional iron-binding capacity approximation; do not treat the two as interchangeable measured assays. Use matching sample context.
  • Use the displayed units and measurements from the same context. Editable fields support arithmetic inverses when enough independent values are supplied. Clear a preset value before solving it as an unknown.
  • This tool performs the stated arithmetic model. It does not establish a diagnosis, prescribe treatment or replace laboratory and clinical assessment.

Common questions

What does this calculation represent?

The direct TIBC ratio and transferrin estimate are separate models. The 70.9 factor uses a conventional iron-binding capacity approximation; do not treat the two as interchangeable measured assays. Use matching sample context.

Can I solve for a different field?

Clear the unknown field and enter enough independent values in the remaining editable controls. A relationship cannot recover a unique value when a dividing quantity is zero.

References

The calculation equations, inverse formulas, units, and input rules were imported from this source. Bookify provides the interface and equation solver.

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