Transferrin Saturation Calculator
A serum iron of 100 mcg/dL with a TIBC of 400 mcg/dL gives a transferrin saturation of 25.0%, within the commonly cited normal range. This transferrin saturation calculator divides serum iron by total iron-binding capacity (TIBC) and multiplies by 100 to produce TSAT as a percentage. Enter both values in the same unit, typically micrograms per deciliter (mcg/dL) on a US lab report, and the tool returns the percentage alongside a general educational reference band.
Quick answer
TSAT (%) equals serum iron divided by TIBC, multiplied by 100.
What this tells you
- •TSAT (%) equals serum iron divided by TIBC, multiplied by 100.
- •Both serum iron and TIBC must be entered in the same concentration unit, typically mcg/dL on a US lab report.
- •The result is grouped into low, normal, or high bands using commonly cited educational reference ranges, not a lab-specific or diagnostic cutoff.
- •TSAT is one marker among several, including ferritin and hemoglobin, that clinicians use together to assess iron status.
How to Use
- 1Enter your serum iron value in mcg/dL, exactly as it appears on your lab report.
- 2Enter your total iron-binding capacity (TIBC) value in mcg/dL from the same report.
- 3Calculate to see TSAT as a percentage and its general reference band.
- 4Compare the result with your lab's own reference range, since cutoffs can vary by laboratory, method, age, and sex.
How It Works
Formula
TSAT (%) = (serum iron / TIBC) x 100
Both values must use the same unit, typically mcg/dL
Example: (100 mcg/dL / 400 mcg/dL) x 100 = 25.0%The calculator divides the serum iron concentration by the total iron-binding capacity, then multiplies the result by 100 to express it as a percentage. TIBC estimates how much iron the blood's transferrin protein could carry if fully loaded, so the ratio describes what fraction of that carrying capacity is currently occupied by iron.
Calculation note: values are processed in the order shown above, using the current input units.
Worked Examples
Normal-range example
100 mcg/dL divided by 400 mcg/dL, times 100, equals 25.0 percent.
Low-range example
40 mcg/dL divided by 450 mcg/dL, times 100, equals 8.9 percent, below the 15 percent cutoff.
High-range example
180 mcg/dL divided by 300 mcg/dL, times 100, equals 60.0 percent, above the 50 percent cutoff.
Commonly Cited TSAT Reference Bands
These general educational reference ranges vary by laboratory, assay, age, sex, and population, and are shown here for context, not diagnosis.
| Band | TSAT range | General educational note |
|---|---|---|
| Low | Below 15% | Often associated with reduced iron availability, commonly seen alongside low serum iron |
| Normal | 15% to 50% | Commonly cited as a typical adult reference range |
| High | Above 50% | Often associated with elevated iron availability or iron overload states |
A clinician interprets TSAT together with ferritin, hemoglobin, and clinical history, not as a stand-alone diagnosis.
How to interpret a calculated TSAT
Serum iron and TIBC should come from the same blood draw. TIBC reflects the total capacity of transferrin, the main iron-transport protein in blood, to bind iron. Serum iron measures how much iron is currently circulating and bound to that transferrin. Dividing one by the other estimates what fraction of the transport capacity is occupied at that moment.
Unit matching matters. This calculator expects both serum iron and TIBC in the same concentration unit, typically micrograms per deciliter (mcg/dL) as reported on most US lab panels. If your lab report uses micromoles per liter (micromol/L) or another unit, convert both values to the same unit before entering them, since dividing mismatched units produces a meaningless ratio.
The bands used here, low below 15 percent, normal from 15 to 50 percent, and high above 50 percent, are commonly cited educational reference ranges. They are not a single universal cutoff. Individual laboratories set their own reference ranges based on their assay method, and those ranges can differ by age, sex, and the reference population used to establish them. Always compare your result against the range printed on your own lab report.
Serum iron varies noticeably throughout the day, generally running higher in the morning and lower in the evening, and can shift with recent meals, supplements, and even the time of your last iron dose. TIBC also responds to factors such as pregnancy, inflammation, liver conditions, and estrogen use. Because both inputs can move independently, a single TSAT value taken at one point in time is a snapshot, not a stable long-term measurement.
Clinicians rarely interpret TSAT alone. Ferritin, which reflects stored iron, and hemoglobin, which reflects the iron actually built into red blood cells, are commonly reviewed alongside TSAT to build a fuller picture of iron status. A low TSAT together with low ferritin points more strongly toward iron deficiency than a low TSAT by itself, and a high TSAT together with elevated ferritin is more suggestive of iron overload than TSAT alone.
This calculator performs only the division and percentage step. It does not know your age, sex, symptoms, medication history, inflammatory status, or any other lab values. It cannot account for acute illness, recent transfusion, iron supplementation, or assay-specific quirks that can shift either input.
A result near a band boundary should not be read as a sharp biological line. Measurement variation between assays, and the natural swings in serum iron and TIBC described above, mean that a value close to 15 percent or 50 percent could reasonably fall on either side on a different day. The calculator rounds TSAT to one decimal place after computing the ratio. Clinical decisions should rely on the full laboratory report and a healthcare professional's interpretation, not the displayed band alone.
Common mistakes
- Entering serum iron or TIBC as zero, which leaves the ratio undefined or meaningless.
- Mixing units, such as entering one value in mcg/dL and the other in micromol/L without converting first.
- Treating a single TSAT result as a confirmed diagnosis of iron deficiency or iron overload instead of one screening marker.
- Combining serum iron and TIBC values drawn from different blood samples or different testing days.
- Ignoring that serum iron has a strong daily rhythm and can shift meaningfully between morning and evening draws.
- Skipping ferritin, hemoglobin, and clinical history when interpreting a borderline TSAT result.
Limitations
This calculator assumes serum iron and TIBC come from the same blood sample and are entered in the same unit, typically mcg/dL. It performs a single division and does not convert between mcg/dL and micromol/L or other units. It cannot account for the time of day the sample was drawn, recent food or iron supplement intake, pregnancy, inflammation, liver disease, estrogen use, hemolysis, or laboratory-specific assay variation. The low, normal, and high bands shown here are general educational reference ranges only. They are not the reference range from your specific laboratory, are not adjusted for age or sex, and are not a diagnosis of iron deficiency, iron overload, hemochromatosis, or any other condition. The tool does not evaluate ferritin, hemoglobin, symptoms, or clinical history.
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