Payne formula, clinical standardStep-by-step calculation shownReviewed by medical professionals
Medical disclaimer: This tool is for educational and clinical reference only. Always interpret lab results in the context of a full clinical assessment. This is not a substitute for professional medical judgment.
Enter Lab ValuesFree · Instant
Normal: 8.5–10.5 mg/dL
Normal: 3.5–5.0 g/dL
Corrected Calcium Result
Corrected Calcium
9.76
mg/dL
Adjustment
+0.96 mg/dL
from 8.8 measured
Normal
Corrected calcium is within the normal reference range.
Calcium Reference Range
4.08.510.516.0
Corrected Ca = 8.8 + 0.8 × (4.0 − 2.8)
= 8.8 + 0.8 × 1.2
= 8.8 + 0.96
= 9.76 mg/dL
The Payne Formula Explained
Corrected Ca (mg/dL) = Measured Ca + 0.8 × (4.0 − Albumin)
About 45% of serum calcium is bound to albumin. When albumin is below 4.0 g/dL, total calcium is falsely low. The Payne formula adjusts for this: for every 1 g/dL drop in albumin below 4.0, add 0.8 mg/dL to the measured calcium.
Normal serum calcium is 8.5–10.5 mg/dL. The corrected value should be interpreted within this range.
Who Is This Calculator For?
🏥
Physicians & NPs
Quick bedside correction for calcium in hypoalbuminemic patients.
🎓
Medical Students
Learn the Payne formula with step-by-step calculation output.
🧪
Lab Technologists
Flag cases where corrected calcium differs significantly from measured.
📚
Nursing Staff
Understand corrected calcium before administering calcium supplementation.
How to Use This Calculator
1
Enter serum calcium
Input total serum calcium in mg/dL from the patient's metabolic panel.
2
Enter serum albumin
Input albumin in g/dL. This is the key correction factor.
3
Read corrected calcium
The corrected value appears instantly alongside the step-by-step calculation.
4
Check the status label
The calculator classifies the result: normal, hypo-, or hypercalcemia.
5
Review the gauge
The color bar shows where the corrected calcium falls relative to the reference range.
6
Use clinically with judgment
The Payne formula is an approximation. In critically ill patients, consider direct ionized calcium.
Worked Example
Dr. Nguyen is reviewing labs for Marcus, a 68-year-old hospitalized patient. His serum calcium reads 7.6 mg/dL and albumin is 2.2 g/dL. Is Marcus truly hypocalcemic?
Corrected Ca = 7.6 + 0.8 × (4.0 − 2.2)
= 7.6 + 0.8 × 1.8
= 7.6 + 1.44
Corrected Ca = 9.04 mg/dL (Normal range: 8.5–10.5)
What Does the Result Mean?
The measured calcium of 7.6 mg/dL appeared low, but Marcus has hypoalbuminemia: his albumin is 1.8 g/dL below the 4.0 reference. After the Payne correction, his true calcium is 9.04 mg/dL, within the normal range. No calcium supplementation is needed. Acting on the uncorrected value would have been a clinical error.
Common Clinical Errors
!
Treating based on uncorrected calcium
In hypoalbuminemic patients, the raw calcium is artificially low. Always correct before initiating supplementation.
!
Over-relying on the formula when albumin < 2.0
The Payne formula becomes less reliable at very low albumin. Use ionized calcium directly in these cases.
!
Forgetting to correct in critically ill patients
ICU patients frequently have hypoalbuminemia. Routine calcium checks should be corrected as a default.
!
Assuming normal albumin without checking
Never assume normal albumin in hospitalized patients. Check the lab value before using total calcium alone.
!
Using mmol/L without converting
This calculator uses mg/dL. If your lab reports in mmol/L, multiply by 4 before entering.
Interpretation of serum total calcium: effects of adjustment for albumin concentration on frequency of abnormal values. J Clin Pathol, 1973.
Payne RB et al. · ncbi.nlm.nih.gov
Should calcium be corrected for albumin? Clinical Biochemistry, 2018.
Lian IA & Asberg A · pubmed.ncbi.nlm.nih.gov
Diagnostic approach to hypocalcemia in adults
UpToDate · uptodate.com
Reviewed By
Dr. Marcus Webb, MD
Hospitalist physician, internal medicine
Dr. Webb practices hospital medicine at a tertiary care center and regularly interprets metabolic panels in complex inpatients. He has taught clinical biochemistry interpretation to medical students and residents for over a decade.
Albumin → Correction
Albumin
Add to Ca
1 g/dL
+2.4
1.5 g/dL
+2.0
2 g/dL
+1.6
2.5 g/dL
+1.2
3 g/dL
+0.8
3.5 g/dL
+0.4
4 g/dL
±0.0
4.5 g/dL
+-0.4
⚕️ Clinical Note
The Payne formula has limitations in critically ill patients and those with severe hypoalbuminemia (albumin < 2.0 g/dL). In these cases, direct ionized calcium measurement provides a more reliable assessment of calcium status.