The Friedewald equation has estimated LDL cholesterol from a standard lipid panel since 1972, long before direct LDL assays became routine. Enter three values from your fasting lipid panel and get the number that drives most cholesterol guidelines.
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Fill in the form and press Calculate. You will get your number, an interpretation chip, and a personalized chart pack drawn instantly in your browser.
- Risk spectrum with your position marked
- Reference ranges from the original publication
- Shareable link, nothing stored
Scientific references
One subtraction away from the answer
Measuring LDL directly used to require ultracentrifugation, a slow and expensive step that no routine lab wanted to run. Friedewald and colleagues noticed in 1972 that very low density lipoprotein cholesterol tracks fasting triglycerides closely enough to be approximated as triglycerides divided by five. Subtract that estimate and HDL from total cholesterol and what remains is LDL. The formula became the default for half a century and still prints on countless lab reports.
Where the math bends
The division by five assumes a typical mix of lipoprotein particles, and that assumption breaks down when triglycerides climb. Above about 400 mg/dL the estimate loses meaning entirely, which is why this calculator caps the triglyceride input there. Nonfasting samples, recent illness, and certain rare lipid disorders also distort the result. Newer alternatives such as the Martin Hopkins method adjust the divisor per person and handle higher triglycerides better, and many large labs have quietly switched to it.
Reading your number
Under 100 mg/dL counts as optimal for most adults, while 190 and above almost always triggers treatment conversations regardless of other risk factors. The space between depends on your overall risk profile, which is why LDL never gets interpreted alone. Pair it with the ASCVD or Framingham score on this site and the picture sharpens considerably.
A note on units
This tool works in mg/dL, the convention in the United States. Most of the rest of the world reports cholesterol in mmol/L. Multiply mg/dL by 0.0259 to convert, or use the cholesterol unit converter on this site before entering your values.