By Zencalcy Editorial TeamLast reviewed About us
The Friedewald equation estimates LDL cholesterol without a direct LDL measurement, using total cholesterol, HDL cholesterol and triglycerides. It assumes that VLDL cholesterol is approximately one fifth of the triglyceride value. The estimate is cheap and widely used, but it loses accuracy when triglycerides are high.
Estimate LDL cholesterol from total, HDL and triglycerides.
LDL = total cholesterol − HDL − triglycerides ÷ 5
All inputs are mg/dL. The equation is valid only when triglycerides are below 400 mg/dL, because the VLDL estimate becomes unreliable above that point. It can also be less accurate at very low LDL values and in some metabolic conditions. A directly measured LDL or a different equation may be preferred in those situations.
| Symbol | Meaning |
|---|---|
| LDL | Estimated low-density lipoprotein cholesterol in mg/dL. |
| total cholesterol | Total cholesterol in mg/dL. |
| HDL | High-density lipoprotein cholesterol in mg/dL. |
| triglycerides | Triglycerides in mg/dL; divided by five as the VLDL estimate. |
The VLDL estimate is 150 ÷ 5 = 30 mg/dL. LDL = 200 − 50 − 30 = 120 mg/dL. Because triglycerides are well below 400, the Friedewald estimate is considered valid. If triglycerides were 420, the calculator would decline to estimate and would recommend a direct LDL measurement instead.
The equation starts from the idea that total cholesterol is the sum of HDL, LDL and VLDL cholesterol. If VLDL cholesterol can be approximated as triglycerides divided by five, then LDL can be solved by subtraction. That approximation is the equation's strength and its weakness: it is convenient, but it depends on a fixed relationship between triglycerides and VLDL cholesterol that does not hold in every person. High triglycerides, diabetes and certain genetic lipid disorders can all distort the ratio. This is why the 400 mg/dL cutoff exists and why a direct LDL measurement is preferred when the estimate matters for treatment. The arithmetic is simple, but the interpretation should stay cautious.
Continue with the Cholesterol Ratio Calculator, Cholesterol Units Converter, or the VLDL Calculator — or browse more metabolic health tools and all health calculators.
The equation assumes VLDL cholesterol is one fifth of triglycerides. At high triglyceride levels that ratio becomes unreliable, so the calculated LDL can be substantially wrong. Most laboratories switch to a direct assay or another equation when triglycerides exceed 400 mg/dL.
Lipid and metabolic calculations are screening aids, not diagnoses. Friedewald LDL is unreliable when triglycerides are high, and risk depends on blood pressure, smoking, diabetes, kidney disease and family history. Treatment decisions require a clinician and, in most cases, a full lipid panel.
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Last reviewed: September 2026. See how we build and check every tool on the about page.
Content updated: September 2026