LDL Calculator

Quick Answer

Last updated: 10 November 2026 ·How we calculate this: the NIH (Sampson 2020) and Friedewald (1972) equations

How This LDL Calculator Works

LDL cholesterol, often called "bad" cholesterol, is usually not measured directly in a standard lipid panel. Labs calculate it from three measured values: total cholesterol, HDL cholesterol and triglycerides. Enter your numbers in mg/dL or mmol/L. The calculator gives LDL with the NIH equation published by Sampson and colleagues in 2020 and with the older Friedewald equation, plus non-HDL cholesterol, two common ratios and the NCEP risk category.

How to Use the LDL Calculator

1. Choose mg/dL or mmol/L to match your lab report.
2. Enter total cholesterol.
3. Enter HDL cholesterol.
4. Enter triglycerides.
5. Press Calculate and read LDL, non-HDL and the category.

LDL Cholesterol Formulas

• Friedewald (1972): LDL = TC − HDL − TG ÷ 5, in mg/dL; not used when TG is 400 mg/dL or more
• NIH / Sampson (2020): LDL = TC ÷ 0.948 − HDL ÷ 0.971 − (TG ÷ 8.56 + TG × non-HDL ÷ 2,140 − TG² ÷ 16,100) − 9.44, in mg/dL, for TG up to 800 mg/dL
• Non-HDL cholesterol: TC − HDL
• Units: cholesterol mmol/L × 38.67 = mg/dL; triglycerides mmol/L × 88.57 = mg/dL

Key Terms

• LDL cholesterol: low-density lipoprotein cholesterol, the main cholesterol that builds up in arteries.
• HDL cholesterol: high-density lipoprotein cholesterol, which helps remove cholesterol.
• Triglycerides: the main type of fat in the blood.
• Non-HDL cholesterol: total cholesterol minus HDL.
• β-quantification: the reference lab method that measures LDL using ultracentrifugation.

Worked Example

A lab reports total cholesterol 240, HDL 38 and triglycerides 420 mg/dL.

• Non-HDL = 240 − 38 = 202 mg/dL
• Friedewald cannot be used because triglycerides are over 400
• NIH: 240 ÷ 0.948 − 38 ÷ 0.971 − (420 ÷ 8.56 + 420 × 202 ÷ 2,140 − 420² ÷ 16,100) − 9.44 = 127 mg/dL
• That is in the near optimal category

Real-Life Examples

• Check a lab report: see how the lab's calculated LDL was found.
• High triglycerides: 240, 38 and 420 mg/dL give an NIH LDL of 127 mg/dL when Friedewald cannot be used.
• mmol/L results: 5.2, 1.3 and 1.7 mmol/L give an LDL of 3.21 mmol/L.
• Track changes: compare LDL before and after diet changes or medicine.

LDL vs HDL vs Non-HDL Cholesterol

• LDL carries cholesterol into artery walls; lower is better.
• HDL carries cholesterol away to the liver; higher is generally better.
• Non-HDL is all the cholesterol in harmful particles, LDL plus VLDL and remnants.

LDL Cholesterol Categories

Doctors may set lower goals for people with heart disease or diabetes.

What Changes LDL and How It Is Used

Diet high in saturated and trans fat, excess weight, inactivity, smoking, genes such as familial hypercholesterolemia, and conditions such as hypothyroidism and kidney disease can all raise LDL. Statins and other medicines lower it. Because LDL builds up in artery walls, doctors use it, together with age, blood pressure, diabetes and smoking, to judge heart attack and stroke risk.

Calculated LDL depends on triglycerides, which rise after eating, so many labs still prefer a fasting sample when triglycerides are high. The Friedewald formula assumes a fixed ratio of triglycerides to VLDL cholesterol; it underestimates LDL when triglycerides are high or LDL is low. The NIH equation was fitted to reference ultracentrifugation results from about 8,600 patients and stays accurate up to 800 mg/dL triglycerides. Non-HDL cholesterol needs no formula and is a good extra check.

Common Mistakes to Avoid

• Mixing units. mg/dL and mmol/L differ by a factor of about 39 for cholesterol.
• Using Friedewald with high triglycerides. It is not valid at 400 mg/dL or more.
• Using the cholesterol factor for triglycerides. Triglycerides convert with 88.57, not 38.67.
• Comparing non-fasting and fasting results. Triglycerides change after meals.
• Reading LDL alone. Overall risk depends on many factors.

Frequently Asked Questions

References & Sources