LDL Cholesterol Calculator

LDL is usually not measured directly: it is estimated from the lipid panel (total cholesterol, HDL and triglycerides). All three formulas share the same logic — LDL = total cholesterol − HDL − VLDL cholesterol — but estimate VLDL cholesterol differently.

1. Friedewald (1972)

LDL = total cholesterol − HDL − (triglycerides / 5)  (in mg/dL; in mmol/L the divisor is 2.2).

This is the historic formula, still the most used in laboratories. It assumes a fixed triglyceride-to-VLDL ratio of 5, an assumption that becomes inaccurate when triglycerides are high or LDL is very low.

2. Martin-Hopkins (2013)

Same structure, but the triglyceride divisor is not fixed at 5: it is an adjustable factor picked from a 180-cell table based on non-HDL cholesterol and triglycerides. This makes the estimate more accurate especially with low LDL and high triglycerides.

3. Sampson/NIH (2020)

A closed-form equation developed at the National Institutes of Health, designed to stay accurate even with hypertriglyceridaemia: it is validated up to triglycerides of 800 mg/dL, well beyond the Friedewald limit.

For a complete picture of the atherogenic profile see also non-HDL cholesterol.

The most important limit to know concerns triglycerides. The Friedewald formula is unreliable when triglycerides exceed 400 mg/dL (about 4.5 mmol/L): in those conditions it tends to underestimate LDL, so the calculator does not show the result and prompts you to switch method. This is a check many online calculators skip.

With very high triglycerides it is worth also checking the metabolic picture: see metabolic syndrome, the HOMA-IR index and the TyG index.

The table above shows the reference bands used by this calculator. In short (NCEP ATP III classification, mg/dL):

Important: the LDL target is personalised to your overall cardiovascular risk: people at high risk (e.g. diabetes, previous heart attack) have lower targets. The result is not a diagnosis and should be interpreted by a doctor.

LDL is the so-called "bad cholesterol": high levels promote atherosclerosis and raise the risk of heart attack and stroke. It is one of the most common reasons for checking a lipid panel, especially with a family history, high blood pressure, diabetes or familial hypercholesterolaemia.

Because weight and metabolism affect the lipid profile, it can help to also check your BMI, your non-HDL cholesterol and your HOMA-IR index.

• Estimated LDL requires a lipid panel: total cholesterol, HDL and triglycerides.
• The blood draw is traditionally done after a 9–12 hour fast, mainly for the triglyceride measurement.
• You can enter the values in mg/dL or mmol/L: select the unit that matches your lab report.

• Lifestyle: a diet low in saturated fat, physical activity, weight control and not smoking all lower LDL.
• Treatment: depending on risk, your doctor may consider medication (e.g. statins). Do not start or stop treatment on your own.

When to see a professional: consult a doctor if your LDL is high, or if you have a family history of cardiovascular disease or other risk factors. Setting the treatment target is the doctor's role.

• They are estimates, not a direct measurement of LDL.
• Friedewald is unreliable with triglycerides above 400 mg/dL or a non-fasting sample, and tends to underestimate LDL when triglycerides are high.
• Martin-Hopkins is more accurate at low LDL and high triglycerides, but its factor table is validated for triglycerides below 400 mg/dL.
• Sampson/NIH extends validity up to 800 mg/dL of triglycerides; above that a direct measurement is needed.