LDL Cholesterol Calculator (Friedewald Equation)

What Is LDL Cholesterol?

Cholesterol is carried through your bloodstream attached to proteins called lipoproteins. The main types are:

• LDL (Low-Density Lipoprotein): “bad” cholesterol. Deposits cholesterol in artery walls, forming plaques that narrow arteries and raise heart attack and stroke risk.
• HDL (High-Density Lipoprotein): “good” cholesterol. Carries cholesterol away from arteries back to the liver.
• VLDL (Very Low-Density Lipoprotein): carries triglycerides; roughly VLDL = Triglycerides / 5 in mg/dL.
• Triglycerides: a type of fat (lipid) in your blood; elevated levels raise cardiovascular risk.

The Friedewald Equation

Developed by William Friedewald in 1972, this formula estimates LDL from the other lipid panel values:

LDL (mg/dL) = Total Cholesterol - HDL - (Triglycerides / 5)

LDL (mmol/L) = Total Cholesterol - HDL - (Triglycerides / 2.17)

Important limitation: This formula is only valid when triglycerides are below 400 mg/dL (4.52 mmol/L). At higher TG levels, direct LDL measurement (ultracentrifugation or the Martin-Hopkins equation) should be used instead.

The second limitation, which almost nobody mentions. Friedewald also drifts at the low end. The fixed divisor of 5 assumes a constant ratio of triglycerides to VLDL cholesterol, and that assumption breaks down when LDL falls below about 70 mg/dL, particularly if triglycerides are above 150. In that corner it tends to underestimate LDL, sometimes by 10 mg/dL or more, which matters a great deal for anyone on a statin working to a target. The Martin-Hopkins equation replaces the fixed 5 with a divisor chosen from a 180-cell table based on the patient’s own triglyceride and non-HDL values, and it is what most large labs now report. If this page returns a number in that range, treat it as a floor rather than a reading, and ask what method your lab used.

Non-HDL Cholesterol

Non-HDL = Total Cholesterol − HDL

It is the crudest calculation on this page and arguably the most useful one. It captures every atherogenic particle at once, LDL plus VLDL plus remnants, needs no assumption about triglycerides, and stays valid when Friedewald does not. Guidelines put the target 30 mg/dL (0.8 mmol/L) above whatever your LDL target is. The calculator reports it alongside LDL.

LDL Classification (AHA/ACC Guidelines)

The calculator also grades the other three values on the panel, using these bands:

The non-HDL bands are simply the LDL bands with 30 mg/dL added, which is exactly how the guidelines define the target.

Lifestyle Factors That Affect LDL

Saturated and trans fats raise LDL. Soluble fiber (oats, beans, lentils) lowers LDL by binding cholesterol in the gut. Regular aerobic exercise raises HDL. Statins (prescription medications) are the most powerful LDL-lowering drugs available, often reducing LDL by 30–50%.

This calculator is for educational purposes only. Always discuss lipid results with your healthcare provider.