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Corrected Calcium Calculator
About half of the calcium in blood is bound to albumin, so a low albumin makes the total calcium look lower than the biologically active level really is. The corrected (or "adjusted") calcium applies the standard bedside formula to estimate what the total calcium would be at a normal albumin.
Enter the values or tick the options above — the result updates automatically.
How to interpret the result
The corrected value is compared with the usual total calcium reference range of roughly 8.5–10.5 mg/dL (about 2.1–2.6 mmol/L). The correction is an estimate: it performs poorly at extremes of albumin, in critical illness, and in kidney failure. When the answer really matters — for example before treating — an ionized (free) calcium measurement is the more reliable test, because it measures the active fraction directly.
If your laboratory reports calcium in mmol/L and albumin in g/L, convert first: calcium mg/dL = mmol/L × 4.0, and albumin g/dL = g/L ÷ 10.
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Frequently asked questions
Why does calcium need correcting for albumin?
Roughly half of total calcium travels bound to albumin. When albumin is low, total calcium falls even though the active, ionized fraction may be unchanged — the correction estimates the total calcium at a normal albumin of 4.0 g/dL.
What is the corrected calcium formula?
Corrected calcium (mg/dL) = measured calcium + 0.8 × (4.0 − albumin in g/dL). In SI units: corrected calcium (mmol/L) = measured calcium + 0.02 × (40 − albumin in g/L).
Is corrected calcium the same as ionized calcium?
No. Ionized calcium is measured directly and reflects the physiologically active fraction. The corrected value is a formula-based estimate of total calcium and can mislead in critical illness, kidney failure, and abnormal pH.
What is a normal corrected calcium?
The corrected value is read against the usual total calcium range of roughly 8.5–10.5 mg/dL (2.1–2.6 mmol/L), but you should always use your own laboratory's reference range.