How is LDL cholesterol calculated?

The Friedewald equation: LDL = Total cholesterol − HDL − (Triglycerides / 5). This formula is valid only when triglycerides are < 400 mg/dL and the patient is fasting. The Martin-Hopkins method is more accurate at low LDL levels and with triglycerides 150–400 mg/dL.

What is a normal LDL cholesterol level?

Optimal LDL is 20%), the target is < 70 mg/dL. Very high-risk patients may benefit from LDL < 55 mg/dL per ESC guidelines. LDL 100–129 is near optimal, 130–159 borderline high, 160–189 high, and ≥ 190 very high.

When is the Friedewald equation inaccurate?

The Friedewald equation is inaccurate when triglycerides > 400 mg/dL, in non-fasting samples, and at very low LDL levels (< 70 mg/dL). In these cases, direct LDL measurement or the Martin-Hopkins equation should be used. The Friedewald equation also overestimates LDL in type III hyperlipoproteinemia.

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LDL Cholesterol Calculator

Calculate LDL-C using the Friedewald equation. Enter total cholesterol, HDL, and triglycerides from a fasting lipid panel.

Inputs

Total Cholesterol (mg/dL)

HDL Cholesterol (mg/dL)

Triglycerides (mg/dL)

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Enter lipid panel values to calculate LDL.

< 70 mg/dLVery high-risk (ASCVD, diabetes + risk factors)

< 100 mg/dLOptimal / high-risk target

100–129 mg/dLNear optimal / above optimal

130–159 mg/dLBorderline high

160–189 mg/dLHigh

≥ 190 mg/dLVery high

Disclaimer: For educational purposes only. Not a substitute for clinical judgment.

When to use

Use this calculator to estimate LDL-C when a direct LDL measurement is unavailable. The Friedewald equation is widely used in clinical practice for fasting lipid panels.

Clinical pearls

The Friedewald equation is inaccurate when triglycerides exceed 400 mg/dL — a direct LDL measurement is required.
The equation assumes VLDL ≈ TG/5. This approximation breaks down with very high or very low TG levels.
Non-fasting specimens may overestimate TG and thus underestimate LDL.
For patients with low LDL (< 70), the Martin-Hopkins equation may be more accurate than Friedewald.

References

Friedewald WT, Levy RI, Fredrickson DS. Estimation of LDL cholesterol in plasma without use of the preparative ultracentrifuge. Clin Chem. 1972;18(6):499-502.
Martin SS, et al. Comparison of a novel method vs the Friedewald equation for estimating LDL-C levels. JAMA. 2013;310(19):2061-2068.

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About This Tool

What Is the Friedewald Equation?

The Friedewald equation, published in 1972, estimates LDL cholesterol from a standard fasting lipid panel: LDL = Total Cholesterol − HDL − (Triglycerides / 5). The TG/5 term approximates VLDL cholesterol. This equation remains the most widely used method for LDL estimation in clinical laboratories worldwide.

Limitations

The equation is invalid when triglycerides exceed 400 mg/dL, in non-fasting samples, or in patients with type III hyperlipoproteinemia (dysbetalipoproteinemia). It also becomes less accurate at very low LDL levels (< 70 mg/dL), which is clinically significant as treatment targets have lowered over time. The Martin-Hopkins equation uses an adjustable TG/VLDL factor and is more accurate across a wider range of TG and LDL levels.

🔑 Clinical Pearls

Friedewald: LDL = TC − HDL − TG/5 (all in mg/dL). In SI units (mmol/L): LDL = TC − HDL − TG/2.2.
Invalid when TG > 400 mg/dL — order a direct LDL measurement.
2018 ACC/AHA guidelines recommend LDL < 70 for very high-risk ASCVD patients; consider adding ezetimibe or PCSK9i if not at goal on max statin.
Non-HDL cholesterol (TC − HDL) is an alternative risk marker that includes VLDL and does not require fasting.

Key References

Friedewald WT, Levy RI, Fredrickson DS. Estimation of LDL cholesterol. Clin Chem. 1972;18(6):499-502.
Martin SS, et al. Comparison of a novel method vs the Friedewald equation. JAMA. 2013;310(19):2061-2068.
Grundy SM, et al. 2018 AHA/ACC Guideline on the Management of Blood Cholesterol. Circulation. 2019;139(25):e1082-e1143.

Formula last verified: February 2026