Corrected calcium calculator
Albumin-corrected serum calcium, with the ionised-calcium caveat stated plainly.
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This is a reference implementation of a published formula, provided for use by qualified healthcare professionals. It does not diagnose, does not account for the individual circumstances of any patient, and is not a recommendation for treatment. Confirm every result against your own institutional guidance before acting on it. Clinical judgement always takes precedence over a calculator.
About this calculation
Roughly 40% of serum calcium is bound to albumin, so total calcium falls as albumin falls without the physiologically active ionised fraction changing. The correction estimates what the total would be at a normal albumin.
Formula
Corrected Ca (mg/dL) = measured Ca + 0.8 × (4.0 − albumin g/dL)
- Source
- Payne RB et al., British Medical Journal (1973)
- Methodology version
- 1.0.0
- Last reviewed
- 2026-10-28
What this does not account for
- The correction is an approximation and performs poorly in critical illness, renal failure and marked acid-base disturbance — the settings where calcium matters most.
- Where the answer will change management, measure ionised calcium directly rather than correcting total calcium.
- Binding is pH-dependent: alkalosis lowers the ionised fraction without changing total calcium, and the correction does not capture that.