Corrected Calcium for Hypoalbuminemia Calculator (Payne Formula

Physiology of Calcium Binding & The Payne Equation

Total serum calcium exists in three distinct physiological fractions in circulation:

• Protein-Bound Calcium (~40–45%): Primarily bound to negatively charged binding sites on serum albumin.

• Complexed / Cheated Calcium (~10–15%): Bound to circulating anions like citrate, phosphate, and bicarbonate.

• Free Ionized Calcium (iCa, ~45–50%): The biologically active, tightly regulated fraction responsible for neuromuscular excitation, myocardial contraction, and coagulation cascade initiation.

Why Correct for Albumin?

When serum albumin drops (in malnutrition, sepsis, hepatic cirrhosis, nephrotic syndrome, or surgical recovery), the total measured calcium falls in direct proportion to the lost albumin binding sites. The Payne formula adds \ of calcium for every \ that albumin falls below the normal baseline of correcting for pseudohypocalcemia.

How to Use This Calculator

Enter your Laboratory Unit Standard — select from Conventional US Units (Calcium in mg/dL, Albumin in g/dL), SI International Units (Calcium in mmol/L, Albumin in g/L), Measured Total Serum Calcium (e.g. 7.8 mg/dL (or 1.95 mmol/L)), and Serum Albumin (e.g. 2.5 g/dL (or 25 g/L)). Results update instantly — no submit button needed. Use metric or imperial units as labeled. For the most accurate result, measure height and weight in the morning without shoes.

The Formula

Corrected Calcium for Hypoalbuminemia equations (Payne Formula):

In Conventional US Units (mg/dL \& g/dL):

Corrected Calcium (mg/dL) = Measured Calcium (mg/dL) + 0.8 × (4.0 - Albumin (g/dL))

In Standard SI Units (mmol/L \& g/L):

Corrected Calcium (mmol/L) = Measured Calcium (mmol/L) + 0.02 × (40 - Albumin (g/L))

Reference Ranges: Normal Calcium: 8.5 - 10.2 mg/dL (2.13 - 2.55 mmol/L); Normal Albumin: 4.0 g/dL (40 g/L).

Worked Example

For example, evaluating a hospitalized patient with measured total calcium \ and serum albumin Albumin deficit is . The correction factor is . Corrected Calcium is demonstrating normal eucalcemia (pseudohypocalcemia).

Understanding Your Result

Health calculations based on standard clinical formulas give a population-reference estimate — individual variation exists. Compare your result to the reference ranges provided using validated sources (WHO, CDC, NIH, or specialty clinical guidelines). A single measurement is a starting point; meaningful health trends emerge from tracking the same metric over time under consistent conditions. For values outside reference ranges, consult a qualified healthcare provider before making changes to diet, exercise, or medication.