{
    "name": "GFR Calculator",
    "url": "https://calculators.geekmidst.com/calculators/gfr-calculator",
    "markdown": "https://calculators.geekmidst.com/calculators/gfr-calculator.md",
    "category": "Health & fitness",
    "description": "Estimate glomerular filtration rate from serum creatinine, age and sex with the race-free CKD-EPI 2021 equation, with the KDIGO GFR category.",
    "summary": "Estimated GFR (eGFR) gauges kidney filtration from a blood creatinine result using the CKD-EPI 2021 equation. It supports, and does not replace, clinical judgement.",
    "also_called": [
        "eGFR calculator",
        "CKD-EPI 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": "creatinine",
            "label": "Serum creatinine",
            "type": "number",
            "default": "1.0"
        },
        {
            "name": "scr_unit",
            "label": "Creatinine unit",
            "type": "segmented",
            "default": "mgdl",
            "options": {
                "mgdl": "mg/dL",
                "umol": "µmol/L"
            }
        },
        {
            "name": "age",
            "label": "Age",
            "type": "number",
            "default": "50",
            "unit": "years"
        },
        {
            "name": "sex",
            "label": "Sex",
            "type": "segmented",
            "default": "male",
            "options": {
                "male": "Male",
                "female": "Female"
            }
        }
    ],
    "outputs": [
        {
            "key": "egfr",
            "label": "eGFR",
            "format": "integer"
        },
        {
            "key": "category",
            "label": "KDIGO GFR category",
            "format": "text"
        },
        {
            "key": "creatinine_mgdl",
            "label": "Creatinine used",
            "format": "number"
        }
    ],
    "formula": {
        "text": "eGFR = 142 × min(Scr/κ, 1)^α × max(Scr/κ, 1)^−1.200 × 0.9938^Age × 1.012 [if female];  κ = 0.7 (F) or 0.9 (M);  α = −0.241 (F) or −0.302 (M)",
        "variables": {
            "Scr": "serum creatinine in mg/dL (µmol/L ÷ 88.4)",
            "Age": "age in years (adults only)",
            "κ, α": "sex-specific constants"
        }
    },
    "worked_example": {
        "inputs": {
            "creatinine": "1.0",
            "scr_unit": "mgdl",
            "age": "50",
            "sex": "male"
        },
        "steps": [
            "Scr/κ = 1.0 ÷ 0.9 = 1.111, so the min term is 1 and the max term is 1.111^−1.200 = 0.881.",
            "Age term: 0.9938^50 = 0.733.",
            "eGFR = 142 × 0.881 × 0.733 ≈ 91.7, reported as 92 mL/min/1.73 m²."
        ],
        "result": "A 50-year-old man with a creatinine of 1.0 mg/dL has an eGFR of about 92 mL/min/1.73 m², KDIGO category G1."
    },
    "interpretation": "KDIGO categories: G1 ≥ 90, G2 60–89, G3a 45–59, G3b 30–44, G4 15–29, G5 < 15 mL/min/1.73 m². Chronic kidney disease is diagnosed only when a reduced GFR or kidney damage (such as albumin in the urine) persists for more than three months, so one result on its own is not a diagnosis.",
    "assumptions": [
        "Adult (18 or over) with stable kidney function.",
        "Creatinine measured with an IDMS-traceable method.",
        "Result is indexed to a standard body surface area of 1.73 m²."
    ],
    "limitations": [
        "Unreliable in acute kidney injury, pregnancy, very high or very low muscle mass (amputation, bodybuilding, frailty), high-protein diets or creatine supplements, and some medicines that change creatinine.",
        "For drug dosing, the product label may specify Cockcroft–Gault creatinine clearance or a non-indexed GFR.",
        "Cystatin C–based equations may be preferred when creatinine is misleading."
    ],
    "rules": null,
    "faqs": [
        {
            "question": "Why does the 2021 equation not use race?",
            "answer": "The CKD-EPI 2021 refit removed the race coefficient used in the 2009 equation, so eGFR now depends only on creatinine, age and sex."
        },
        {
            "question": "Is my eGFR low because of age?",
            "answer": "eGFR falls gradually with age in most people. Whether a value matters depends on trends over time, urine albumin and other findings, which a clinician interprets."
        }
    ],
    "sources": [
        {
            "title": "National Kidney Foundation: CKD-EPI Creatinine Equation (2021)",
            "url": "https://www.kidney.org/professionals/ckd-epi-creatinine-equation-2021"
        }
    ],
    "related": [
        {
            "name": "Body Surface Area Calculator",
            "url": "https://calculators.geekmidst.com/calculators/body-surface-area-calculator"
        },
        {
            "name": "BMI Calculator",
            "url": "https://calculators.geekmidst.com/calculators/bmi-calculator"
        },
        {
            "name": "Age Calculator",
            "url": "https://calculators.geekmidst.com/calculators/age-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"
}