LDL Cholesterol Calculator (Friedewald)

What does LDL cholesterol mean?

Low-density lipoprotein (LDL) cholesterol, often called "bad cholesterol", is the primary carrier of cholesterol in the bloodstream. Elevated LDL causes atherosclerosis by depositing cholesterol into arterial walls, forming plaques that narrow and harden vessels over time. This process is a primary driver of heart attack and stroke.

The Friedewald equation (1972) estimates LDL from a standard lipid panel: LDL = Total Cholesterol − HDL − (Triglycerides ÷ 5) in mg/dL. The triglyceride term approximates VLDL cholesterol, which is not directly measured in a routine fasting panel. This approximation breaks down when triglycerides exceed 400 mg/dL (4.5 mmol/L); above that level, a direct LDL measurement is needed.

LDL particles vary in size and density. Small, dense LDL particles are considered more atherogenic than large, buoyant ones. However, routine lipid panels do not distinguish particle size; total LDL-C remains the primary treatment target in most major guidelines.

Multiple factors affect LDL: saturated and trans fats raise it; unsaturated fats, soluble fibre, plant sterols, and statins lower it. Genetic conditions such as familial hypercholesterolaemia cause severely elevated LDL irrespective of diet.

Reference ranges (ACC/AHA 2018)

When should you see a doctor?

An LDL above 4.1 mmol/L (160 mg/dL) warrants medical review. An LDL ≥ 4.9 mmol/L (190 mg/dL) may indicate familial hypercholesterolaemia, which typically requires statin therapy regardless of other risk factors. Even lower LDL values may need treatment if you have diabetes, established cardiovascular disease, or high Framingham risk, your overall risk profile matters more than any single number.