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Corrected Calcium Calculator

Adjusts total serum calcium for low or high albumin with the Payne formula, in conventional (mg/dL, g/dL) or SI units (mmol/L, g/L), and reports both unit systems.

When to use

You have a total calcium and albumin and want the albumin-adjusted calcium used to screen for hypo- or hypercalcaemia.

Do not use when: An ionised calcium measurement is available (it is more accurate, especially in critical illness, acid-base disorders or renal failure).

Formula

Conventional: corrected_Ca (mg/dL) = calcium + 0.8 × (4.0 − albumin_g_dl). SI: corrected_Ca (mmol/L) = calcium + 0.02 × (40 − albumin_g_l). 1 mmol/L = 4.008 mg/dL.

Payne (1973) assumes 0.8 mg/dL of calcium is bound per 1 g/dL of albumin; the correction performs poorly in chronic kidney disease and critical illness, where ionised calcium should be measured. Results are informational only and not a substitute for clinical judgement or medical advice.

Inputs

Parameter	Type	Required	Description
`calcium`	number	yes	Measured total serum calcium in the unit system chosen below. Range: > 0, ≤ 20
`albumin`	number	yes	Serum albumin: g/dL for the conventional system, g/L for SI. Range: > 0, ≤ 70
`unit_system`	enum: conventional \| si	default conventional	Units of the two inputs.

Outputs

Output	Type	Unit	Description
`corrected_calcium`	number		Albumin-corrected calcium in the input unit.
`corrected_calcium_mg_dl`	number	mg/dL	Corrected calcium in mg/dL (mmol/L × 4.008).
`corrected_calcium_mmol_l`	number	mmol/L	Corrected calcium in mmol/L (mg/dL × 0.2495).
`interpretation`	string		Against a typical adult range of 8.5–10.5 mg/dL (2.12–2.62 mmol/L); laboratory ranges vary.

Example

Calcium 8.0 mg/dL, albumin 2.5 g/dL: {"calcium":8,"albumin":2.5,"unit_system":"conventional"} → {"corrected_calcium":9.2,"corrected_calcium_mmol_l":2.3,"interpretation":"Within the typical range (8.5–10.5 mg/dL)"}

Calcium 2.10 mmol/L, albumin 30 g/L: {"calcium":2.1,"albumin":30,"unit_system":"si"} → {"corrected_calcium":2.3,"corrected_calcium_mg_dl":9.22}

GET https://tttkmbb.com/api/v1/calculate/corrected-calcium?calcium=8&albumin=2.5&unit_system=conventional

Machine access

API: GET https://tttkmbb.com/api/v1/calculate/corrected-calcium (query parameters) or POST with a JSON body {"inputs": {...}}
Schema: https://tttkmbb.com/api/v1/calculators/corrected-calcium · Markdown: https://tttkmbb.com/medical/corrected-calcium.md · JSON definition: https://tttkmbb.com/medical/corrected-calcium.json
MCP: server https://tttkmbb.com/mcp, tool run_calculator with calculator_id="corrected-calcium"
OpenAPI operationId: calculate_corrected_calcium
Freshness: static. Authentication: none. Rate limit: fair use (see rate limits).

Sources

Payne RB, Little AJ, Williams RB, Milner JR (1973) Interpretation of serum calcium in patients with abnormal serum proteins, Br Med J 4:643-646 (peer_reviewed)

FAQ

My lab reports albumin in g/L; which system do I use?

Choose si and enter calcium in mmol/L and albumin in g/L (a g/dL value × 10).

When is the correction unreliable?

In renal failure, after surgery, with abnormal pH, paraproteins or very low albumin the formula misclassifies many patients; ionised calcium is the reference.

Related calculators

Anion Gap Calculator — Albumin also changes the expected anion gap.
eGFR Calculator — Kidney function affects calcium interpretation.