{
    "name": "Corrected Calcium Calculator",
    "url": "https://calculators.geekmidst.com/calculators/corrected-calcium-calculator",
    "markdown": "https://calculators.geekmidst.com/calculators/corrected-calcium-calculator.md",
    "category": "Healthcare operations",
    "description": "Adjust total serum calcium for a low or high albumin with the Payne formula, in mg/dL or mmol/L, for use by healthcare professionals.",
    "summary": "The Payne formula adds 0.8 mg/dL of calcium for every 1 g/dL that albumin is below the reference value. It supports, and does not replace, clinical judgement; ionised calcium is the direct measurement.",
    "also_called": [
        "Albumin-adjusted calcium calculator"
    ],
    "applies_to": "Worldwide",
    "last_updated": "2026-10-29",
    "computation": "Results are computed in the visitor’s browser on the HTML page. This API describes the calculator; it does not compute results.",
    "inputs": [
        {
            "name": "units",
            "label": "Units",
            "type": "segmented",
            "default": "conventional",
            "options": {
                "conventional": "mg/dL, g/dL",
                "si": "mmol/L, g/L"
            }
        },
        {
            "name": "calcium",
            "label": "Total serum calcium",
            "type": "number",
            "default": "8.0"
        },
        {
            "name": "albumin",
            "label": "Serum albumin",
            "type": "number",
            "default": "2.0"
        },
        {
            "name": "normal_albumin",
            "label": "Reference albumin",
            "type": "number",
            "default": "4.0"
        }
    ],
    "outputs": [
        {
            "key": "corrected",
            "label": "Corrected calcium (in the units entered)",
            "format": "number"
        },
        {
            "key": "corrected_mg_dl",
            "label": "Corrected calcium",
            "format": "number"
        },
        {
            "key": "corrected_mmol_l",
            "label": "Corrected calcium",
            "format": "number"
        },
        {
            "key": "adjustment",
            "label": "Adjustment added",
            "format": "number"
        }
    ],
    "formula": {
        "text": "Corrected Ca (mg/dL) = Measured Ca + 0.8 × (Reference albumin − Measured albumin in g/dL);  mmol/L = mg/dL ÷ 4.0078",
        "variables": {
            "Measured Ca": "total serum calcium",
            "Albumin": "serum albumin (g/L ÷ 10 = g/dL)",
            "4.0078": "mg/dL per mmol/L of calcium (molar mass 40.078 g/mol)"
        }
    },
    "worked_example": {
        "inputs": {
            "units": "conventional",
            "calcium": "8.0",
            "albumin": "2.0",
            "normal_albumin": "4.0"
        },
        "steps": [
            "Albumin deficit = 4.0 − 2.0 = 2.0 g/dL.",
            "Adjustment = 0.8 × 2.0 = 1.6 mg/dL.",
            "Corrected calcium = 8.0 + 1.6 = 9.6 mg/dL (9.6 ÷ 4.0078 = 2.40 mmol/L)."
        ],
        "result": "A total calcium of 8.0 mg/dL with albumin 2.0 g/dL corrects to 9.6 mg/dL (2.40 mmol/L) by the Payne formula."
    },
    "interpretation": "Compare the corrected value with your laboratory’s reference range for total calcium. When the result would change management, or in critical illness, measure ionised calcium directly instead of relying on the correction.",
    "assumptions": [
        "The Payne correction factor of 0.8 mg/dL per g/dL of albumin applies.",
        "SI values are converted to mg/dL and g/dL, corrected, and converted back."
    ],
    "limitations": [
        "The correction is known to be unreliable in critical illness, advanced kidney disease and acid–base disturbance; ionised calcium is preferred there.",
        "Different laboratories validate different correction equations; use your laboratory’s if it reports one."
    ],
    "rules": null,
    "faqs": [
        {
            "question": "What is the SI version of the formula?",
            "answer": "It is commonly written as Ca + 0.02 × (40 − albumin in g/L) mmol/L. This calculator converts units exactly instead, and the two agree to about 0.01 mmol/L."
        },
        {
            "question": "Is corrected calcium the same as ionised calcium?",
            "answer": "No. Corrected calcium estimates what total calcium would be at a normal albumin; ionised calcium is the free, active fraction measured directly."
        }
    ],
    "sources": [
        {
            "title": "WikEM: Corrected calcium (Payne RB et al., BMJ 1973;4:643–646)",
            "url": "https://wikem.org/wiki/Corrected_calcium_calculator"
        }
    ],
    "related": [
        {
            "name": "Anion Gap Calculator",
            "url": "https://calculators.geekmidst.com/calculators/anion-gap-calculator"
        },
        {
            "name": "Creatinine Clearance Calculator (Cockcroft–Gault)",
            "url": "https://calculators.geekmidst.com/calculators/creatinine-clearance-estimate-calculator"
        },
        {
            "name": "Molarity Calculator",
            "url": "https://calculators.geekmidst.com/calculators/molarity-calculator"
        }
    ],
    "disclaimer": "This is a general screening estimate for adults, not medical advice or a diagnosis. Talk to a qualified health professional about your health.",
    "publisher": "GM¹X CalcVerse"
}