Free tool

Transferrin Saturation Calculator (Iron ÷ TIBC)

Q: What is a normal transferrin saturation?

Roughly 20–45% in adults; laboratories print ranges such as 15–50% or 20–50%. Because serum iron varies by the hour and with meals, a value is best read from a morning fasting draw and together with ferritin, which reflects the iron stores themselves.

Q: What does a low transferrin saturation mean?

Under about 16% there is too little iron for the carrying capacity. With a low ferritin that is iron deficiency — from periods, blood loss in the gut, low intake or malabsorption — and the cause is worth finding, not just the iron replacing. With a normal or high ferritin it is usually the anemia of chronic inflammation, where iron is present but sequestered.

Q: When does a high saturation suggest hemochromatosis?

The ACG and AASLD guidelines use a fasting transferrin saturation of 45% or more, usually with an elevated ferritin, as the trigger to repeat the test and order HFE genotyping. Iron supplements, a recent transfusion, hemolysis and liver disease also raise saturation, so a single value on supplements is repeated after stopping them.

Q: My report shows transferrin, not TIBC — can I still use this?

Yes. TIBC can be estimated from transferrin: multiply transferrin in mg/dL by about 1.39 (some laboratories use 1.42) to get TIBC in µg/dL, then enter that value. The estimate differs slightly from a measured TIBC, which the limits section notes.

The short answer

Divide serum iron by total iron-binding capacity and multiply by 100 to get transferrin saturation — the share of iron-carrying capacity actually loaded with iron. About 20–45% is usual; under 16% is the iron-deficient pattern (or iron locked away by inflammation when ferritin is normal), and 45% or more is the screening threshold for iron overload that prompts a repeat fasting test and HFE gene testing.

Inputs: Serum iron · TIBC
Usual: ≈ 20–45%
Overload screen: ≥ 45% → repeat + HFE
Cost: Free

Serum iron

µg/dL

Morning, fasting draw — iron swings through the day · Iron range

TIBC (total iron-binding capacity)

µg/dL

If your report lists transferrin (mg/dL) instead, TIBC ≈ transferrin × 1.39 · TIBC range

Enter your values to calculate.

Transferrin saturation [%] = serum iron ÷ TIBC × 100 · UIBC = TIBC − serum iron

Educational — a derived index, not a diagnosis. Nothing you enter leaves your browser.

How the Transferrin saturation is calculated

Transferrin saturation [%] = serum iron ÷ TIBC × 100 · UIBC = TIBC − serum iron

Worked example

Serum iron (µg/dL)	TIBC (total iron-binding capacity) (µg/dL)	Transferrin saturation (%)
60	380	16

Unsaturated iron-binding capacity (UIBC): 320 µg/dL

Falls in: Low.

How to read the result

Transferrin saturation	Reads as	What it usually means
< 16	Low	Saturation under about 16% is the iron-deficient pattern — too little iron for the carrying capacity. With a low ferritin it is iron deficiency (from blood loss, periods, diet or malabsorption); with a normal or high ferritin it is more often the anemia of chronic inflammation, where iron is present but locked away. Finding the cause matters as much as replacing iron.
16 – 20	Borderline low	16–20% is the gray zone, especially on a single afternoon or non-fasting sample — serum iron can swing by a third through the day. Repeat on a morning fasting draw and read it with ferritin before concluding anything.
20 – 45	Within the usual range	About 20–45% is the usual adult range (laboratories print 15–50 or 20–50). Iron stores and carrying capacity are in proportion.
≥ 45	Elevated	A saturation of 45% or more is the screening threshold for iron overload: guidelines call for a repeat fasting saturation with ferritin and, if still high, HFE gene testing for hereditary hemochromatosis. Iron supplements, recent transfusion, liver disease and hemolysis also raise it; a single value on supplements is repeated after a pause.

Cut points reviewed by Youmna DiStefano, MD on 2026-10-12. Sources below.

Limits

Serum iron, and therefore saturation, varies by the hour and with meals, supplements, inflammation and recent transfusion, so one value is a screen and the repeat is on a morning fasting sample. TIBC calculated from transferrin (× 1.39–1.42) differs slightly from measured TIBC. The bands are for adults; children, pregnancy and oral contraceptives (which raise transferrin) read differently. Saturation alone does not define iron deficiency or overload — ferritin and, where relevant, genetic testing complete the picture.

Sources

Kowdley KV, Brown KE, Ahn J, Sundaram V. ACG Clinical Guideline: Hereditary Hemochromatosis. Am J Gastroenterol 2019;114:1202–1218. doi.org/10.14309/ajg.0000000000000315
Adams PC, et al. Hemochromatosis and Iron-Overload Screening in a Racially Diverse Population (HEIRS). N Engl J Med 2005;352:1769–1778. doi.org/10.1056/NEJMoa041534
Camaschella C. Iron-Deficiency Anemia. N Engl J Med 2015;372:1832–1843. doi.org/10.1056/NEJMra1401038
Bacon BR, Adams PC, Kowdley KV, Powell LW, Tavill AS. Diagnosis and management of hemochromatosis: 2011 practice guideline by the AASLD. Hepatology 2011;54:328–343. doi.org/10.1002/hep.24330

Frequently asked questions

What is a normal transferrin saturation?

Roughly 20–45% in adults; laboratories print ranges such as 15–50% or 20–50%. Because serum iron varies by the hour and with meals, a value is best read from a morning fasting draw and together with ferritin, which reflects the iron stores themselves.

What does a low transferrin saturation mean?

Under about 16% there is too little iron for the carrying capacity. With a low ferritin that is iron deficiency — from periods, blood loss in the gut, low intake or malabsorption — and the cause is worth finding, not just the iron replacing. With a normal or high ferritin it is usually the anemia of chronic inflammation, where iron is present but sequestered.

When does a high saturation suggest hemochromatosis?

The ACG and AASLD guidelines use a fasting transferrin saturation of 45% or more, usually with an elevated ferritin, as the trigger to repeat the test and order HFE genotyping. Iron supplements, a recent transfusion, hemolysis and liver disease also raise saturation, so a single value on supplements is repeated after stopping them.

My report shows transferrin, not TIBC — can I still use this?

Yes. TIBC can be estimated from transferrin: multiply transferrin in mg/dL by about 1.39 (some laboratories use 1.42) to get TIBC in µg/dL, then enter that value. The estimate differs slightly from a measured TIBC, which the limits section notes.

Which biomarkers does this tool cover?

Which tests give you these numbers?

Physician-authorized, drawn at Quest, Labcorp or BioReference. Results in 1–3 business days for most tests.