Estimate LDL ('bad') cholesterol from total cholesterol, HDL and triglycerides — by the classic Friedewald equation and the newer Martin–Hopkins method.
Friedewald is unreliable when triglycerides are 400 mg/dL or higher, or when not fasting — the calculator says so instead of guessing.
LDL (Friedewald)
—How to use this tool
From a lipid panel, in mg/dL.
The 'good' cholesterol, in mg/dL.
Fasting values work best — the equations assume a fasting sample.
Friedewald and Martin–Hopkins side by side, with the LDL category.
Formula & worked example
Total 200, HDL 50, triglycerides 150: Friedewald gives 200 − 50 − 30 = 120 mg/dL. Martin–Hopkins uses a factor of 4.9 for this band, giving 200 − 50 − 30.6 = 119 mg/dL. Both sit in the near-optimal band (100–129).
Limitations — read this before you rely on it
Both equations estimate LDL, they do not measure it, and both assume a fasting sample. Neither is reliable when triglycerides are 400 mg/dL or higher — the calculator refuses those instead of guessing. The Martin–Hopkins factors here are simplified (rounded) from the published table, so the Martin figure is an approximation of the lab method. A lab-reported direct LDL always prevails.
Frequently asked questions
Low-density lipoprotein — the 'bad' cholesterol that can build up in artery walls. Lower is generally better.
Friedewald is the classic 1972 equation with a fixed divisor of 5. Martin–Hopkins (2013) adjusts that divisor by your levels and is more accurate, especially when LDL is low.
Under 100 mg/dL is optimal for most people; people at high cardiovascular risk are often given lower targets by their clinician.
Triglycerides rise after eating, which drags the estimate down. A fasting sample keeps the maths honest.
Neither equation works there. Ask your lab for a direct LDL measurement instead.