LDL cholesterol calculator
Enter your lipid panel, get the estimated LDL.
How is LDL cholesterol calculated?
With the Friedewald equation: LDL = total cholesterol − HDL − triglycerides ÷ 5, all in mg/dL. This is the estimate used in the NIH’s ATP III cholesterol guidelines.
Example
Total cholesterol 200, HDL 50 and triglycerides 150: 200 − 50 − 30 = 120 mg/dL.
When can’t it be used?
ATP III: when triglycerides are over 400 mg/dL, the estimate is not accurate. The calculator stops there; a lab can measure LDL directly.
What LDL level is optimal?
ATP III classifies LDL below 100 mg/dL as optimal, 100–129 as near or above optimal, 130–159 borderline high, 160–189 high and 190 or more very high.
What about total and HDL cholesterol?
ATP III: total cholesterol below 200 is desirable, 200–239 borderline high, 240 or more high. HDL below 40 is low and 60 or more is high. MedlinePlus gives different targets for people 19 and younger.
Why does the equation divide triglycerides by 5?
Total cholesterol is carried by LDL, HDL and VLDL particles. Friedewald, Levy and Fredrickson (Clinical Chemistry, 1972) estimated the VLDL part as triglycerides ÷ 5 so that LDL could be found by subtraction, without an ultracentrifuge. The fixed factor of 5 is an approximation. In a 2013 JAMA study of 1,350,908 lipid profiles, Martin and colleagues found that the real ratio of triglycerides to VLDL cholesterol varied, with a median of 5.2, and proposed an adjustable factor taken from a table of 180 cells based on triglyceride and non-HDL cholesterol levels.
Worked example: the same panel at three triglyceride levels
Take a total cholesterol of 180 mg/dL and an HDL of 45 mg/dL. With triglycerides of 150, the VLDL estimate is 150 ÷ 5 = 30 and LDL = 180 − 45 − 30 = 105 mg/dL. With triglycerides of 350, the estimate is 70 and LDL = 180 − 45 − 70 = 65 mg/dL. With triglycerides of 450 the equation is not used and the calculator gives no value, because it would be unreliable above 400 mg/dL. The same total and HDL cholesterol thus give very different LDL values depending on how much of the total is assigned to VLDL.
How accurate is a calculated LDL?
A calculated value is less exact than a direct measurement. Sampson and colleagues (JAMA Cardiology, 2020), who analyzed 8,656 patients at the NIH Clinical Center, note that calculated LDL cholesterol is less accurate when LDL is low or triglycerides are 400 mg/dL or higher, and they proposed a newer equation for those cases. Labs may use the Friedewald or the Martin equation, or measure LDL directly, so a lab’s printed LDL can differ from this calculator’s result.
Common mistakes with calculated LDL
Entering results in mmol/L: the divisor of 5 belongs to mg/dL, so a panel reported in mmol/L must be converted first, or the answer will be wrong. Using the equation above 400 mg/dL of triglycerides. Treating the estimate as a measurement when the number is close to a cutoff such as 100 or 160 mg/dL, where a small error changes the category. Applying adult ATP III categories to a child; MedlinePlus gives different targets for people 19 and younger. And interpreting the number without the rest of the picture: guidelines set treatment goals by overall cardiovascular risk, which your clinician assesses.
Sources and related calculators
Sources: W. T. Friedewald, R. I. Levy and D. S. Fredrickson, “Estimation of the concentration of low-density lipoprotein cholesterol in plasma, without use of the preparative ultracentrifuge,” Clinical Chemistry (1972); S. S. Martin et al., “Comparison of a novel method vs the Friedewald equation for estimating low-density lipoprotein cholesterol levels from the standard lipid profile,” JAMA (2013); M. Sampson et al., “A new equation for calculation of low-density lipoprotein cholesterol in patients with normolipidemia and/or hypertriglyceridemia,” JAMA Cardiology (2020); NCEP Adult Treatment Panel III (NHLBI). Related: blood pressure calculator, BMI calculator and waist-to-height ratio calculator.
For general information only — not medical advice. Talk with your doctor or another health professional about your own health. How we check our calculators.