LDL Cholesterol (Friedewald) Calculator

LDL = TC − HDL − TG/5 (mg/dL). Friedewald 1972 Clin Chem. Not valid if triglycerides > 400 mg/dL.

Inputs

Fasting. Friedewald invalid if >400.

Result

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How to use this calculator

  • Enter fasting lipid panel values in mg/dL.
  • Read LDL + non-HDL + ATP III risk category.
  • If TG > 400, the formula is invalid — order a direct LDL.

About this calculator

Friedewald formula: LDL = TC − HDL − TG/5 (mg/dL only; TG/2.2 if mmol/L). Source: 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. Assumes VLDL = TG/5. **Invalid when TG > 400 mg/dL** (VLDL/TG ratio diverges) or in type III hyperlipidemia. Modern alternatives: Martin-Hopkins (Martin SS et al., JAMA 2013;310:2061), NIH equation (Sampson 2020), or direct LDL measurement. NCEP ATP III categories (LDL mg/dL): <100 optimal, 100-129 near optimal, 130-159 borderline, 160-189 high, ≥190 very high. **Not medical advice.**

Frequently asked

Source of the formula?+
Friedewald, Levy, Fredrickson, Clinical Chemistry 1972;18:499-502. Original article based on ultracentrifuge cross-validation.
Why TG/5?+
In typical fasting samples, VLDL cholesterol ≈ TG / 5 (mg/dL). Breaks down at high TG when chylomicrons / IDL contribute.
Friedewald vs. Martin-Hopkins?+
Martin-Hopkins (2013) uses adjustable TG-to-VLDL ratio (varies 3.1-11.9 by TG and non-HDL); more accurate at low LDL or high TG. Many US labs default to Martin-Hopkins now.
When invalid?+
TG > 400 mg/dL; type III dysbetalipoproteinemia; non-fasting samples; chylomicronemia syndromes. Use direct LDL.
Treatment thresholds?+
Per ACC/AHA 2018 (Grundy et al., Circulation): high-intensity statin if ASCVD or LDL ≥190; moderate-intensity in adults 40-75 with diabetes or 10-yr ASCVD risk ≥7.5%.
Is this medical advice?+
No. Educational. Lipid management requires full risk profile + clinician.

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