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Corrected Calcium Calculator

Calculate albumin-corrected serum calcium with the Payne formula in conventional or SI units, with clinical classification.

Normal albumin: 4.0 g/dL or 40 g/L. Without albumin no correction is possible.

Reference Ranges (corrected calcium)

Hypocalcemia

Symptoms: tetany, paresthesia, cramps

< 8.5 mg/dL · < 2.12 mmol/L
Normal

Albumin-corrected normal range

8.5 – 10.2 mg/dL · 2.12 – 2.55 mmol/L
Hypercalcemia

DDx: HPT, malignancy, vitamin D toxicity

> 10.2 mg/dL · > 2.55 mmol/L

The Payne correction is unreliable in severe acid-base disturbances. Ionized calcium is the gold standard. This calculator does not replace clinical diagnosis.

Frequently Asked Questions

Why correct calcium for albumin?+
About 40% of serum calcium is bound to albumin. In hypoalbuminemia the measured total calcium appears falsely low even though the physiologically active ionized calcium may be normal. The Payne formula compensates for this effect.
What is the Payne formula?+
Corrected Ca [mg/dL] = Total Ca + 0.8 × (4.0 − Albumin [g/dL]). In SI units: Corrected Ca [mmol/L] = Total Ca + 0.02 × (40 − Albumin [g/L]).
When is the correction unreliable?+
In severe acid-base disturbances, multiple myeloma (paraprotein-related pseudohypercalcemia), and in critically ill patients. In those cases, ionized calcium should be measured directly.
Which normal albumin value is used?+
The formula uses 4.0 g/dL (or 40 g/L) as the reference. At exactly this albumin value, no correction occurs — total and corrected calcium are identical.
Does this calculator replace medical diagnosis?+
No. Albumin-corrected calcium is an interpretation aid and must be considered together with clinical context (symptoms, PTH, vitamin D, kidney function).

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Corrected Calcium Calculator: Albumin Correction (Payne Formula)

7 min