{
  "id": "ldl",
  "version": "4151adcecc13",
  "status": "published",
  "name": "LDL Calculator",
  "question": "What is my LDL cholesterol?",
  "summary": "Estimates LDL cholesterol from total cholesterol, HDL cholesterol, and triglycerides with the Friedewald or the Sampson (NIH) equation, in mg/dL or mmol/L, and shows its NCEP ATP III category.",
  "category": "health",
  "subcategory": "clinical",
  "url": "https://www.acalculator.org/health/ldl-calculator",
  "markdown": "https://www.acalculator.org/health/ldl-calculator.md",
  "kind": "function",
  "method": "Friedewald: LDL = TC − HDL − TG ÷ 5 (mg/dL, TG under 400). Sampson NIH equation 2: LDL = TC/0.948 − HDL/0.971 − (TG/8.56 + TG × non-HDL/2140 − TG²/16100) − 9.44 (mg/dL, TG up to 800). SI values convert with 0.02586 (cholesterol) and 0.0113 (triglycerides) mmol/L per mg/dL.",
  "assumptions": [
    "Total cholesterol, HDL cholesterol, and triglycerides come from the same blood sample.",
    "The LDL estimate is worked from the exact typed values and rounded once: to a whole mg/dL, and to 2 decimals in mmol/L.",
    "The ATP III category is read from the whole mg/dL value shown."
  ],
  "inputs": {
    "$schema": "https://json-schema.org/draft/2020-12/schema",
    "type": "object",
    "properties": {
      "units": {
        "title": "Units",
        "description": "US units (mg/dL) or SI units (mmol/L).",
        "type": "string",
        "enum": [
          "us",
          "si"
        ]
      },
      "method": {
        "title": "Equation",
        "description": "Friedewald (1972), for triglycerides under 400 mg/dL, or Sampson NIH equation 2 (2020), for triglycerides up to 800 mg/dL.",
        "type": "string",
        "enum": [
          "friedewald",
          "sampson"
        ]
      },
      "tc": {
        "title": "Total cholesterol (mg/dL)",
        "description": "Total cholesterol, 50 to 1,000 mg/dL.",
        "type": "number",
        "minimum": 50,
        "maximum": 1000
      },
      "tcSi": {
        "title": "Total cholesterol (mmol/L)",
        "description": "Total cholesterol, 1.3 to 25.9 mmol/L.",
        "type": "number",
        "minimum": 1.3,
        "maximum": 25.9
      },
      "hdl": {
        "title": "HDL cholesterol (mg/dL)",
        "description": "HDL (\"good\") cholesterol, 5 to 200 mg/dL.",
        "type": "number",
        "minimum": 5,
        "maximum": 200
      },
      "hdlSi": {
        "title": "HDL cholesterol (mmol/L)",
        "description": "HDL (\"good\") cholesterol, 0.13 to 5.17 mmol/L.",
        "type": "number",
        "minimum": 0.13,
        "maximum": 5.17
      },
      "tg": {
        "title": "Triglycerides (mg/dL)",
        "description": "Triglycerides, 10 to 3,000 mg/dL.",
        "type": "number",
        "minimum": 10,
        "maximum": 3000
      },
      "tgSi": {
        "title": "Triglycerides (mmol/L)",
        "description": "Triglycerides, 0.11 to 33.9 mmol/L.",
        "type": "number",
        "minimum": 0.11,
        "maximum": 33.9
      }
    }
  },
  "outputs": {
    "ldl": {
      "label": "LDL cholesterol (mg/dL)",
      "description": "The estimated LDL cholesterol, in mg/dL, to a whole number.",
      "format": "number"
    },
    "ldlSi": {
      "label": "LDL cholesterol (mmol/L)",
      "description": "The same estimate in mmol/L (mg/dL × 0.02586), to 2 decimals.",
      "format": "number"
    },
    "category": {
      "label": "ATP III category",
      "description": "The NCEP ATP III band of the LDL value.",
      "format": "text"
    },
    "nonHdl": {
      "label": "Non-HDL cholesterol (mg/dL)",
      "description": "Total cholesterol minus HDL cholesterol, in mg/dL, to a whole number.",
      "format": "number"
    },
    "nonHdlSi": {
      "label": "Non-HDL cholesterol (mmol/L)",
      "description": "Total cholesterol minus HDL cholesterol, in mmol/L, to 2 decimals.",
      "format": "number"
    }
  },
  "defaultAnswer": {
    "inputs": {
      "units": "us",
      "method": "friedewald",
      "tc": 200,
      "tcSi": 5.2,
      "hdl": 50,
      "hdlSi": 1.3,
      "tg": 150,
      "tgSi": 1.7
    },
    "outputs": {
      "ldl": 120,
      "ldlSi": 3.1,
      "category": "Near or above optimal (100 to 129 mg/dL)",
      "nonHdl": 150,
      "nonHdlSi": 3.88
    },
    "text": "The estimated LDL cholesterol is 120 mg/dL (3.1 mmol/L): Near or above optimal (100 to 129 mg/dL)."
  },
  "examples": [
    {
      "given": {
        "units": "us",
        "method": "friedewald",
        "tc": 200,
        "hdl": 50,
        "tg": 150
      },
      "expect": {
        "ldl": 120,
        "ldlSi": 3.1,
        "category": "Near or above optimal (100 to 129 mg/dL)",
        "nonHdl": 150,
        "nonHdlSi": 3.88
      },
      "source": "Friedewald 1972: 200 − 50 − 150 ÷ 5 = 120 mg/dL; 120 × 0.02586 = 3.103 mmol/L; ATP III 100 to 129 (hand calculation in content.mdx)"
    },
    {
      "given": {
        "units": "us",
        "method": "sampson",
        "tc": 200,
        "hdl": 50,
        "tg": 150
      },
      "expect": {
        "ldl": 123,
        "ldlSi": 3.19,
        "category": "Near or above optimal (100 to 129 mg/dL)"
      },
      "source": "Sampson 2020 NIH equation 2: 210.970 − 51.493 − (17.523 + 10.514 − 1.398) − 9.44 = 123.397 mg/dL (hand calculation in content.mdx, Python 3 check)"
    },
    {
      "given": {
        "units": "us",
        "method": "sampson",
        "tc": 260,
        "hdl": 35,
        "tg": 500
      },
      "expect": {
        "ldl": 133,
        "ldlSi": 3.45,
        "category": "Borderline high (130 to 159 mg/dL)",
        "nonHdl": 225
      },
      "source": "Sampson 2020 NIH equation 2 = 133.323 mg/dL (hand calculation in content.mdx, Python 3 check)"
    },
    {
      "given": {
        "units": "us",
        "method": "friedewald",
        "tc": 240,
        "hdl": 40,
        "tg": 300
      },
      "expect": {
        "ldl": 140,
        "ldlSi": 3.62,
        "category": "Borderline high (130 to 159 mg/dL)",
        "nonHdl": 200
      },
      "source": "Friedewald 1972: 240 − 40 − 60 = 140 mg/dL; ATP III 130 to 159 (hand calculation)"
    },
    {
      "given": {
        "units": "si",
        "method": "friedewald",
        "tcSi": 5.2,
        "hdlSi": 1.3,
        "tgSi": 1.7
      },
      "expect": {
        "ldl": 121,
        "ldlSi": 3.12,
        "nonHdlSi": 3.9
      },
      "source": "5.2 ÷ 0.02586 = 201.083, 1.3 ÷ 0.02586 = 50.271, 1.7 ÷ 0.0113 = 150.442 mg/dL; 201.083 − 50.271 − 30.088 = 120.724 mg/dL; × 0.02586 = 3.122 mmol/L (hand calculation in content.mdx)"
    }
  ],
  "sources": [
    "Friedewald WT, Levy RI, Fredrickson DS. Estimation of the concentration of low-density lipoprotein cholesterol in plasma, without use of the preparative ultracentrifuge. Clin Chem. 1972;18(6):499-502. https://doi.org/10.1093/clinchem/18.6.499 (retrieved 2026-10-05)",
    "Sampson M, Ling C, Sun Q, et al. A new equation for calculation of low-density lipoprotein cholesterol in patients with normolipidemia and/or hypertriglyceridemia. JAMA Cardiol. 2020;5(5):540-548. https://doi.org/10.1001/jamacardio.2020.0013 (open at https://pmc.ncbi.nlm.nih.gov/articles/PMC7240357/, retrieved 2026-10-05)",
    "The NIH equation 2 written out in text: Assessing the practical differences in LDL-C estimates calculated by Friedewald, Martin/Hopkins, or NIH equation 2. https://pmc.ncbi.nlm.nih.gov/articles/PMC10548185/ (retrieved 2026-10-05)",
    "Expert Panel on Detection, Evaluation, and Treatment of High Blood Cholesterol in Adults. Executive summary of the third report of the National Cholesterol Education Program (NCEP) Adult Treatment Panel III. JAMA. 2001;285(19):2486-2497. https://doi.org/10.1001/jama.285.19.2486 (retrieved 2026-10-05)",
    "Nelson RH. Hyperlipidemia as a risk factor for cardiovascular disease. Prim Care. 2013;40(1):195-211. Table 1 reproduces the ATP III classification of LDL, total, and HDL cholesterol and triglycerides. https://pmc.ncbi.nlm.nih.gov/articles/PMC3572442/ (retrieved 2026-10-05)"
  ],
  "related": [],
  "changelog": [
    {
      "date": "2026-10-05",
      "note": "Published after this site's editorial review against the cited sources (no clinician review); the page notices say so."
    }
  ]
}