Transferrin Saturation Calculator
Transferrin saturation (TSAT) tells you what share of your iron-transport capacity is actually loaded with iron. It's computed from two values on a standard iron panel — serum iron and TIBC (total iron-binding capacity) — and it's one of the most useful single numbers for reading iron status, alongside ferritin.
From the same fasting draw as TIBC
Report only shows transferrin? See the FAQ below
Enter your values above to see your results.
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How it works
The formula
TSAT = (serum iron ÷ TIBC) × 100. Example: serum iron 90 µg/dL with TIBC 340 µg/dL gives 26.5%. If your report is in µmol/L, convert both values to µg/dL first (multiply by 5.587) — or just divide one by the other, since the conversion factor cancels out as long as both inputs use the same unit.
No TIBC on your report?
Some panels report transferrin instead of TIBC. A commonly used approximation is TIBC (µg/dL) ≈ transferrin (mg/dL) × 1.25 — a rough estimate, since the exact relationship varies slightly between assays. If precision matters, ask your lab whether a calculated TIBC is available.
TSAT and ferritin work as a pair
Ferritin reflects iron stores; TSAT reflects iron in circulation and transport. Low TSAT with low ferritin points one way ( depleted stores ), low TSAT with normal or high ferritin points another ( iron stuck in storage, often with inflammation ). Neither number alone tells the whole story — and both shift with recent meals, time of day, and illness, so fasting morning draws are the convention.
Evidence level & limitations
The 20–50% window and the thresholds above are laboratory and textbook conventions, not official guideline cut-offs. A single TSAT is a screening signal, not a diagnosis — persistent abnormalities in either direction deserve a practitioner's workup.
Frequently asked questions
How do I calculate transferrin saturation?
Divide serum iron by TIBC and multiply by 100 — both values from the same blood draw. Example: serum iron 90 µg/dL ÷ TIBC 340 µg/dL × 100 = 26.5%. The calculator above does it instantly and adds the interpretation band.
How do I calculate transferrin saturation from TIBC?
TIBC is one of the two required inputs — you don't derive it, you use it directly: TSAT = (serum iron ÷ TIBC) × 100. If your report shows transferrin instead of TIBC, the common approximation is TIBC ≈ transferrin (mg/dL) × 1.25.
What is a normal transferrin saturation?
Most references cite 20–50% for adults. Below 20% is read as a low-iron signal, and persistently above 50% as a high-iron signal. These are laboratory conventions — your lab's printed reference range comes first.
My report is in µmol/L — do I need to convert?
Not for the ratio itself: as long as serum iron and TIBC use the same unit, the conversion factor cancels out. To compare against the 20–50% bands you can enter µmol/L values directly — the percentage is identical either way.
Is low transferrin saturation the same as iron deficiency?
Not by itself. TSAT below 20% is a low-iron signal, but inflammation can push iron into storage and lower TSAT even when total stores are adequate — which is why TSAT is always read alongside ferritin. It's a screening signal that guides the next conversation, not a diagnosis.
Should I fast before the blood draw?
Yes — serum iron swings with recent meals and time of day, so a morning fasting draw is the convention for iron panels. Comparing results across draws is most meaningful when the conditions match.
Sources
- Fairbanks VF, Beutler E. Iron metabolism. In: Williams Hematology — transferrin saturation reference conventions.
- Camaschella C, Nai A, Silvestri L. Iron metabolism and iron disorders revisited in the hepcidin era. Haematologica, 2020.
This calculator is for informational purposes only and is not medical advice, diagnosis, or treatment. Reference ranges are general population guidelines — always discuss your lab results with a qualified healthcare professional.