What is the corrected calcium (Payne) formula?

Bedside Payne-style formula (US): Corrected Ca (mg/dL) = Total Ca + 0.8 × (4.0 − albumin g/dL). SI: Corrected Ca (mmol/L) = Total Ca + 0.02 × (40 − albumin g/L). Worked labs: Ca 8.8 mg/dL + alb 2.5 g/dL → 10.0 mg/dL; same case Ca 2.20 mmol/L + alb 25 g/L → 2.50 mmol/L. Classic albumin-adjustment literature: Payne et al. Br Med J 1973 (DOI 10.1136/bmj.4.5893.643).

Corrected calcium mg/dL vs mmol/L — which units do I use?

Match your lab report. US panels usually report calcium in mg/dL with albumin in g/dL (use the 0.8 / 4.0 formula). SI reports often use mmol/L calcium with albumin in g/L (use 0.02 / 40). Do not mix unit systems in one calculation. Rough conversion: calcium mg/dL ≈ mmol/L × 4; albumin g/dL ≈ g/L ÷ 10.

When should you calculate corrected calcium?

Whenever albumin is abnormal (especially low) and you only have total calcium. Low albumin falsely lowers total calcium; correction estimates what calcium would be at a normal albumin. Prefer ionized calcium in critical illness, ESRD, or when pH is markedly abnormal.

What is a normal corrected calcium?

Teaching ranges used here: 8.5–10.5 mg/dL (2.12–2.62 mmol/L). Lab reference intervals vary slightly. Values below suggest hypocalcemia; above suggest hypercalcemia — confirm clinically and often with ionized calcium / PTH.

Corrected calcium vs ionized calcium?

Corrected calcium is a quick estimate from total Ca + albumin. Ionized (free) calcium is the physiologically active fraction and the gold standard when precision matters. Correction formulas ignore pH, citrate, and many binding shifts common in ICU and dialysis patients.

Do I need correction if albumin is normal?

If albumin is about 4.0 g/dL (40 g/L), the correction term is ~0 and total calcium already reflects the teaching estimate. Still use ionized calcium when symptoms and total calcium disagree.

Is this calculator medical advice?

No. It applies the standard teaching albumin-correction arithmetic for education. Diagnosis and treatment require licensed clinicians and appropriate labs.

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Electrolytes · Payne formula

Corrected Calcium Calculator

Direct answer — Payne corrected calcium formula

Corrected calcium calculator (Payne-style): Corrected Ca (mg/dL) = Total Ca + 0.8 × (4.0 − albumin g/dL). SI units: Total Ca + 0.02 × (40 − albumin g/L). Worked labs: Ca 8.8 mg/dL + albumin 2.5 g/dL → 10 mg/dL (normal corrected despite low total). Teaching normal: 8.5–10.5 mg/dL (2.12–2.62 mmol/L). Prefer ionized calcium in ICU / ESRD. Education only — Payne et al. Br Med J. 1973;4:643-646.

Payne formula, mg/dL vs mmol/L units, and worked labs first — then the interactive calculator. Last updated: August 9, 2026.

Payne formula (albumin-corrected calcium)

Bedside formulas used by this calculator. Classic albumin-adjustment paper: Payne et al. Br Med J. 1973;4:643-646.

Payne-style corrected calcium formulas
Units	Formula	Worked example
mg/dL (US / conventional)	Corrected Ca = Total Ca + 0.8 × (4.0 − albumin g/dL)	Ca 8.8, alb 2.5 → 8.8 + 1.2 = 10.0 mg/dL
mmol/L (SI)	Corrected Ca = Total Ca + 0.02 × (40 − albumin g/L)	Ca 2.20, alb 25 → 2.20 + 0.30 = 2.50 mmol/L

Units: mg/dL vs mmol/L
Item	mg/dL system	mmol/L system
Total calcium units	mg/dL	mmol/L
Albumin units	g/dL	g/L
Reference albumin	4.0 g/dL	40 g/L
Correction factor	0.8 mg/dL per g/dL alb	0.02 mmol/L per g/L alb
Teaching normal range	8.5 – 10.5 mg/dL	2.12 – 2.62 mmol/L

Never mix systems (e.g. mg/dL calcium with g/L albumin) in one calculation.

Worked labs example

Classic hypoalbuminemia (US units)

Labs: total Ca 8.8 mg/dL, albumin 2.5 g/dL
Albumin deficit = 4.0 − 2.5 = 1.5 g/dL
Correction = 0.8 × 1.5 = 1.2 mg/dL
Corrected Ca = 8.8 + 1.2 = 10.0 mg/dL (normal teaching range)

8.8 + 0.8 × (4 − 2.5) = 10.00 mg/dL → Normal

Same case (SI units)

Labs: total Ca 2.20 mmol/L, albumin 25 g/L
Albumin deficit = 40 − 25 = 15 g/L
Correction = 0.02 × 15 = 0.30 mmol/L
Corrected Ca = 2.20 + 0.30 = 2.50 mmol/L (normal teaching range)

2.2 + 0.02 × (40 − 25) = 2.50 mmol/L → Normal

Calculate corrected calcium

Toggle mg/dL or mmol/L to match the Payne formulas above. Result shows arithmetic string and teaching band.

Payne-style mg/dL and mmol/L formulas

Worked labs + unit table above the form

Ionized-calcium preference callouts

Prefer ionized Ca when precision matters

Correction formulas ignore pH, citrate, and many ICU binding shifts. Use ionized calcium for critical decisions.

Corrected Calcium Calculator

Albumin-corrected serum calcium (Payne-style formula)

Units

Total Calcium (mg/dL)

Normal range: 8.5–10.5 mg/dL

Albumin (g/dL)

Normal range: 3.5–5.0 g/dL

Calculation Results

Corrected Calcium:

9.9 mg/dL

9.5 + 0.8 × (4 − 3.5) = 9.90 mg/dL

Interpretation:

Normal

Normal Range:

8.5 – 10.5 mg/dL

Clinical Analysis:

Corrected calcium is within the teaching normal range. Interpret with symptoms, ionized calcium when available, and clinical context.

Medical Disclaimer:

• Educational only — not a diagnosis
• Prefer ionized calcium in critical illness / ESRD
• Always interpret with clinical context and lab reference ranges

Corrected calcium normal ranges

Teaching cutoffs for interpretation on this page — confirm against your laboratory reference interval.

Band	mg/dL	mmol/L	Note
Hypocalcemia	< 8.5 mg/dL	< 2.12 mmol/L	Consider Vit D, PTH, Mg²⁺, CKD — confirm with ionized Ca when critical
Normal (teaching)	8.5 – 10.5 mg/dL	2.12 – 2.62 mmol/L	Lab reference intervals may vary ±0.1–0.2
Hypercalcemia	> 10.5 mg/dL	> 2.62 mmol/L	Consider PTH, malignancy, Vit D toxicity, thiazides

When to correct calcium (and when not)

Situation	Action
Low albumin (malnutrition, cirrhosis, nephrosis)	Correct total Ca — hypoalbuminemia falsely lowers total Ca
High albumin (dehydration, rare)	Correct — hyperalbuminemia can raise total Ca
Albumin ≈ 4.0 g/dL (40 g/L)	Correction ≈ 0 — total Ca already usable
Critical illness, shock, massive transfusion	Prefer ionized calcium — binding shifts with pH/lactate
ESRD / dialysis	Prefer ionized Ca — Payne formula less reliable
Acute alkalosis or acidosis	Prefer ionized Ca — pH alters binding; formula ignores pH

Example corrected calcium results (computed)

Default — Ca 9.5, alb 3.5

9.9 mg/dL

Normal

Worked labs — Ca 8.8, alb 2.5

10 mg/dL

Low total → normal corrected

Same case — SI units

2.5 mmol/L

Ca 2.20, alb 25 g/L

Masked high — Ca 10.2, alb 2.0

11.8 mg/dL

Hypercalcemia (High)

Worked example: hypoalbuminemia ladder

Same total calcium (8.8 mg/dL) across falling albumin — correction rises as albumin falls.

Total Ca	Albumin	Corrected	Band	Arithmetic
8.8	2	10.4 mg/dL	Normal	8.8 + 0.8 × (4 − 2) = 10.40 mg/dL
8.8	2.5	10 mg/dL	Normal	8.8 + 0.8 × (4 − 2.5) = 10.00 mg/dL
8.8	3	9.6 mg/dL	Normal	8.8 + 0.8 × (4 − 3) = 9.60 mg/dL
8.8	4	8.8 mg/dL	Normal	8.8 + 0.8 × (4 − 4) = 8.80 mg/dL
9.5	3.5	9.9 mg/dL	Normal	9.5 + 0.8 × (4 − 3.5) = 9.90 mg/dL

Step-by-step: Ca 8.8 + albumin 2.5

Classic “low total, normal corrected” teaching case

1. Albumin deficit = 4.0 − 2.5 = 1.5 g/dL

2. Correction = 0.8 × 1.5 = 1.2 mg/dL

3. Corrected Ca = 8.8 + 1.2 = 10 mg/dL

4. Interpretation: Normal (8.5 – 10.5 mg/dL)

References

Payne RB, Little AJ, Williams RB, Milner JR. Interpretation of serum calcium in patients with abnormal serum proteins. Br Med J. 1973;4:643–646.Classic albumin-adjustment literature. DOI: 10.1136/bmj.4.5893.643. This calculator uses the common bedside 0.8 / 0.02 factors taught with Payne-style correction.
Prefer ionized calcium when binding conditions are unstable (critical illness, ESRD, marked acid-base disorders).

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Electrolytes · Payne formula

Corrected Calcium Calculator

Direct answer — Payne corrected calcium formula

Payne formula, mg/dL vs mmol/L units, and worked labs first — then the interactive calculator. Last updated: August 9, 2026.

Payne formula (albumin-corrected calcium)

Bedside formulas used by this calculator. Classic albumin-adjustment paper: Payne et al. Br Med J. 1973;4:643-646.

Payne-style corrected calcium formulas
Units	Formula	Worked example
mg/dL (US / conventional)	Corrected Ca = Total Ca + 0.8 × (4.0 − albumin g/dL)	Ca 8.8, alb 2.5 → 8.8 + 1.2 = 10.0 mg/dL
mmol/L (SI)	Corrected Ca = Total Ca + 0.02 × (40 − albumin g/L)	Ca 2.20, alb 25 → 2.20 + 0.30 = 2.50 mmol/L

Units: mg/dL vs mmol/L
Item	mg/dL system	mmol/L system
Total calcium units	mg/dL	mmol/L
Albumin units	g/dL	g/L
Reference albumin	4.0 g/dL	40 g/L
Correction factor	0.8 mg/dL per g/dL alb	0.02 mmol/L per g/L alb
Teaching normal range	8.5 – 10.5 mg/dL	2.12 – 2.62 mmol/L

Never mix systems (e.g. mg/dL calcium with g/L albumin) in one calculation.

Worked labs example

Classic hypoalbuminemia (US units)

Labs: total Ca 8.8 mg/dL, albumin 2.5 g/dL
Albumin deficit = 4.0 − 2.5 = 1.5 g/dL
Correction = 0.8 × 1.5 = 1.2 mg/dL
Corrected Ca = 8.8 + 1.2 = 10.0 mg/dL (normal teaching range)

8.8 + 0.8 × (4 − 2.5) = 10.00 mg/dL → Normal

Same case (SI units)

Labs: total Ca 2.20 mmol/L, albumin 25 g/L
Albumin deficit = 40 − 25 = 15 g/L
Correction = 0.02 × 15 = 0.30 mmol/L
Corrected Ca = 2.20 + 0.30 = 2.50 mmol/L (normal teaching range)

2.2 + 0.02 × (40 − 25) = 2.50 mmol/L → Normal

Calculate corrected calcium

Toggle mg/dL or mmol/L to match the Payne formulas above. Result shows arithmetic string and teaching band.

Payne-style mg/dL and mmol/L formulas

Worked labs + unit table above the form

Ionized-calcium preference callouts

Prefer ionized Ca when precision matters

Correction formulas ignore pH, citrate, and many ICU binding shifts. Use ionized calcium for critical decisions.

Corrected Calcium Calculator

Albumin-corrected serum calcium (Payne-style formula)

Units

Total Calcium (mg/dL)

Normal range: 8.5–10.5 mg/dL

Albumin (g/dL)

Normal range: 3.5–5.0 g/dL

Calculation Results

Corrected Calcium:

9.9 mg/dL

9.5 + 0.8 × (4 − 3.5) = 9.90 mg/dL

Interpretation:

Normal

Normal Range:

8.5 – 10.5 mg/dL

Clinical Analysis:

Corrected calcium is within the teaching normal range. Interpret with symptoms, ionized calcium when available, and clinical context.

Medical Disclaimer:

• Educational only — not a diagnosis
• Prefer ionized calcium in critical illness / ESRD
• Always interpret with clinical context and lab reference ranges

Corrected calcium normal ranges

Teaching cutoffs for interpretation on this page — confirm against your laboratory reference interval.

Band	mg/dL	mmol/L	Note
Hypocalcemia	< 8.5 mg/dL	< 2.12 mmol/L	Consider Vit D, PTH, Mg²⁺, CKD — confirm with ionized Ca when critical
Normal (teaching)	8.5 – 10.5 mg/dL	2.12 – 2.62 mmol/L	Lab reference intervals may vary ±0.1–0.2
Hypercalcemia	> 10.5 mg/dL	> 2.62 mmol/L	Consider PTH, malignancy, Vit D toxicity, thiazides

When to correct calcium (and when not)

Situation	Action
Low albumin (malnutrition, cirrhosis, nephrosis)	Correct total Ca — hypoalbuminemia falsely lowers total Ca
High albumin (dehydration, rare)	Correct — hyperalbuminemia can raise total Ca
Albumin ≈ 4.0 g/dL (40 g/L)	Correction ≈ 0 — total Ca already usable
Critical illness, shock, massive transfusion	Prefer ionized calcium — binding shifts with pH/lactate
ESRD / dialysis	Prefer ionized Ca — Payne formula less reliable
Acute alkalosis or acidosis	Prefer ionized Ca — pH alters binding; formula ignores pH

Example corrected calcium results (computed)

Default — Ca 9.5, alb 3.5

9.9 mg/dL

Normal

Worked labs — Ca 8.8, alb 2.5

10 mg/dL

Low total → normal corrected

Same case — SI units

2.5 mmol/L

Ca 2.20, alb 25 g/L

Masked high — Ca 10.2, alb 2.0

11.8 mg/dL

Hypercalcemia (High)

Worked example: hypoalbuminemia ladder

Same total calcium (8.8 mg/dL) across falling albumin — correction rises as albumin falls.

Total Ca	Albumin	Corrected	Band	Arithmetic
8.8	2	10.4 mg/dL	Normal	8.8 + 0.8 × (4 − 2) = 10.40 mg/dL
8.8	2.5	10 mg/dL	Normal	8.8 + 0.8 × (4 − 2.5) = 10.00 mg/dL
8.8	3	9.6 mg/dL	Normal	8.8 + 0.8 × (4 − 3) = 9.60 mg/dL
8.8	4	8.8 mg/dL	Normal	8.8 + 0.8 × (4 − 4) = 8.80 mg/dL
9.5	3.5	9.9 mg/dL	Normal	9.5 + 0.8 × (4 − 3.5) = 9.90 mg/dL

Step-by-step: Ca 8.8 + albumin 2.5

Classic “low total, normal corrected” teaching case

1. Albumin deficit = 4.0 − 2.5 = 1.5 g/dL

2. Correction = 0.8 × 1.5 = 1.2 mg/dL

3. Corrected Ca = 8.8 + 1.2 = 10 mg/dL

4. Interpretation: Normal (8.5 – 10.5 mg/dL)

References

Payne RB, Little AJ, Williams RB, Milner JR. Interpretation of serum calcium in patients with abnormal serum proteins. Br Med J. 1973;4:643–646.Classic albumin-adjustment literature. DOI: 10.1136/bmj.4.5893.643. This calculator uses the common bedside 0.8 / 0.02 factors taught with Payne-style correction.
Prefer ionized calcium when binding conditions are unstable (critical illness, ESRD, marked acid-base disorders).