LDL Cholesterol (Friedewald) Calculator

How it is calculated

The Friedewald equation estimates LDL by subtracting the other cholesterol fractions from the total: LDL = TC − HDL − TG / 5. TC is total cholesterol, HDL is HDL cholesterol and TG is triglycerides, all in mg/dL. The TG / 5 part is the estimate of VLDL cholesterol, which the tool also shows. Non-HDL cholesterol is TC − HDL. Results are rounded to whole numbers. The tool only accepts plausible mg/dL values: total cholesterol 50 to 1000, HDL 5 to 200 and triglycerides 10 to 400. Anything outside gives no result, as does a case where the estimated LDL would be negative. Triglycerides above 400 mg/dL are refused because the VLDL approximation is unreliable there. Values in mmol/L must be converted to mg/dL first.

Common mistakes

• Entering results in mmol/L. A panel reported as 5.4, 1.4 and 1.6 is far below the accepted mg/dL ranges, so the tool shows no result; multiply cholesterol by about 38.7 and triglycerides by about 88.6 first.
• Using a very high triglyceride result. Above 400 mg/dL the tool gives no result, and near that level the estimate is already weak.
• Mixing up LDL and non-HDL. Non-HDL (155 in the example) is always higher than LDL because it also counts VLDL.
• Swapping HDL and total cholesterol. If HDL is typed larger than the total, the estimate goes negative and the tool returns nothing.
• Treating the rounded whole number as exact. The tool rounds each figure to an integer, and the lab's own method may differ by several mg/dL.