{
  "id": "gfr",
  "version": "d91c19c77935",
  "status": "published",
  "name": "GFR Calculator",
  "question": "What is my GFR?",
  "summary": "Estimates glomerular filtration rate (eGFR) for adults from serum creatinine, cystatin C, or both, with the race-free 2021 CKD-EPI equations, and shows the KDIGO GFR category.",
  "category": "health",
  "subcategory": "clinical",
  "url": "https://www.acalculator.org/health/gfr-calculator",
  "markdown": "https://www.acalculator.org/health/gfr-calculator.md",
  "kind": "function",
  "method": "CKD-EPI 2021 creatinine: 142 × min(Scr/κ, 1)^α × max(Scr/κ, 1)^−1.200 × 0.9938^age × 1.012 (women), κ 0.7 (women) or 0.9 (men), α −0.241 (women) or −0.302 (men); CKD-EPI 2021 creatinine-cystatin C and 2012 cystatin C as stated in content.mdx. Scr in mg/dL, Scys in mg/L.",
  "assumptions": [
    "Adults 18 and older with stable kidney function (not acute kidney injury).",
    "Creatinine is IDMS-standardized and cystatin C is standardized to the IFCC reference material. µmol/L is converted with 1 mg/dL = 88.4 µmol/L.",
    "The equations do not use race (Inker 2021; NKF-ASN Task Force 2021).",
    "eGFR is per 1.73 m² of body surface area and is rounded to a whole number; the KDIGO category is read from the whole number."
  ],
  "inputs": {
    "$schema": "https://json-schema.org/draft/2020-12/schema",
    "type": "object",
    "properties": {
      "eq": {
        "title": "Equation",
        "description": "Which CKD-EPI equation: creatinine only, creatinine with cystatin C, or cystatin C only.",
        "type": "string",
        "enum": [
          "cr",
          "cr-cys",
          "cys"
        ]
      },
      "units": {
        "title": "Creatinine units",
        "description": "US units (mg/dL) or SI units (µmol/L) for serum creatinine.",
        "type": "string",
        "enum": [
          "us",
          "si"
        ]
      },
      "scr": {
        "title": "Serum creatinine (mg/dL)",
        "description": "Serum creatinine from the blood test, in mg/dL (IDMS-standardized, as labs report it).",
        "type": "number",
        "minimum": 0.1,
        "maximum": 20
      },
      "scrSi": {
        "title": "Serum creatinine (µmol/L)",
        "description": "Serum creatinine from the blood test, in µmol/L.",
        "type": "number",
        "minimum": 8.84,
        "maximum": 1768
      },
      "cys": {
        "title": "Cystatin C (mg/L)",
        "description": "Serum cystatin C from the blood test, in mg/L (standardized to the IFCC reference material).",
        "type": "number",
        "minimum": 0.2,
        "maximum": 10
      },
      "age": {
        "title": "Age",
        "description": "Age in whole years. The equations are for adults 18 and older.",
        "type": "integer",
        "minimum": 18,
        "maximum": 110
      },
      "sex": {
        "title": "Sex",
        "description": "Sex at birth, which the equations use.",
        "type": "string",
        "enum": [
          "male",
          "female"
        ]
      }
    }
  },
  "outputs": {
    "egfr": {
      "label": "Estimated GFR",
      "description": "eGFR in mL/min/1.73 m², rounded to a whole number as labs report it.",
      "format": "integer"
    },
    "stage": {
      "label": "KDIGO GFR category",
      "description": "The KDIGO 2012 GFR category (G1 to G5) for the whole-number eGFR.",
      "format": "text"
    },
    "scrOther": {
      "label": "Creatinine in the other unit",
      "description": "The creatinine you entered, converted with 1 mg/dL = 88.4 µmol/L.",
      "format": "text"
    }
  },
  "defaultAnswer": {
    "inputs": {
      "eq": "cr",
      "units": "us",
      "scr": 1,
      "scrSi": 88,
      "cys": 0.9,
      "age": 50,
      "sex": "male"
    },
    "outputs": {
      "egfr": 92,
      "stage": "G1: normal or high",
      "scrOther": "88 µmol/L"
    },
    "text": "Your estimated GFR is 92 mL/min/1.73 m², KDIGO category G1: normal or high."
  },
  "examples": [
    {
      "given": {
        "eq": "cr",
        "units": "us",
        "scr": 1,
        "age": 50,
        "sex": "male"
      },
      "expect": {
        "egfr": 92,
        "stage": "G1: normal or high"
      },
      "source": "Inker et al., N Engl J Med 2021 (CKD-EPI 2021 creatinine): 142 × (1.0/0.9)^−1.200 × 0.9938^50 = 91.69, shown as 92 (hand calculation in content.mdx; Python 3 check in docs/progress/WP-88.md)"
    },
    {
      "given": {
        "eq": "cr",
        "units": "si",
        "scrSi": 132.6,
        "age": 70,
        "sex": "female"
      },
      "expect": {
        "egfr": 37,
        "stage": "G3b: moderately to severely decreased",
        "scrOther": "1.50 mg/dL"
      },
      "source": "Inker et al. 2021: 132.6 ÷ 88.4 = 1.5 mg/dL; 142 × (1.5/0.7)^−1.200 × 0.9938^70 × 1.012 = 37.26, shown as 37 (hand calculation in content.mdx)"
    },
    {
      "given": {
        "eq": "cr-cys",
        "units": "us",
        "scr": 1.2,
        "cys": 1.1,
        "age": 60,
        "sex": "male"
      },
      "expect": {
        "egfr": 71,
        "stage": "G2: mildly decreased"
      },
      "source": "Inker et al. 2021 (creatinine-cystatin C): 135 × (1.2/0.9)^−0.544 × (1.1/0.8)^−0.778 × 0.9961^60 = 71.28, shown as 71 (hand calculation in content.mdx)"
    },
    {
      "given": {
        "eq": "cys",
        "cys": 1.4,
        "age": 45,
        "sex": "female"
      },
      "expect": {
        "egfr": 49,
        "stage": "G3a: mildly to moderately decreased"
      },
      "source": "Inker et al., N Engl J Med 2012 (CKD-EPI cystatin C): 133 × (1.4/0.8)^−1.328 × 0.996^45 × 0.932 = 49.22, shown as 49 (hand calculation in content.mdx)"
    }
  ],
  "sources": [
    "Inker LA, Eneanya ND, Coresh J, et al. New creatinine- and cystatin C-based equations to estimate GFR without race. N Engl J Med. 2021;385(19):1737-1749. https://doi.org/10.1056/NEJMoa2102953 (retrieved 2026-09-28)",
    "Inker LA, Schmid CH, Tighiouart H, et al. Estimating glomerular filtration rate from serum creatinine and cystatin C. N Engl J Med. 2012;367(1):20-29. https://doi.org/10.1056/NEJMoa1114248 (retrieved 2026-09-28)",
    "Delgado C, Baweja M, Crews DC, et al. A unifying approach for GFR estimation: recommendations of the NKF-ASN Task Force on reassessing the inclusion of race in diagnosing kidney disease. Am J Kidney Dis. 2022;79(2):268-288. https://doi.org/10.1053/j.ajkd.2021.08.003 (retrieved 2026-09-28)",
    "KDIGO 2012 Clinical Practice Guideline for the Evaluation and Management of Chronic Kidney Disease. Kidney Int Suppl. 2013;3(1):1-150. https://kdigo.org/guidelines/ckd-evaluation-and-management/ (GFR categories G1 to G5; 1 mg/dL creatinine = 88.4 µmol/L; retrieved 2026-09-28)"
  ],
  "related": [],
  "changelog": [
    {
      "date": "2026-09-29",
      "note": "Published after this site's editorial review against the cited sources (no clinician review); the page notice says so."
    }
  ]
}