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LDL Cholesterol Calculator (Friedewald & Martin-Hopkins)

Calculate LDL cholesterol from total cholesterol, HDL and triglycerides with the Friedewald equation (LDL = TC − HDL − TG/5) and the more accurate Martin-Hopkins and Sampson equations, plus non-HDL cholesterol.

Units

Total cholesterol

HDL cholesterol

Triglycerides (fasting)

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How it works

Friedewald: LDL = TC − HDL − TG/5 (mg/dL; TG/2.2 in mmol/L). Martin-Hopkins: LDL = TC − HDL − TG/factor (factor 3.1–7.0 from TG and non-HDL). Sampson: LDL = TC/0.948 − HDL/0.971 − (TG/8.56 + TG×nonHDL/2140 − TG²/16100) − 9.44

Most laboratories do not measure LDL cholesterol directly; they estimate it. The 1972 Friedewald equation assumes VLDL cholesterol is one fifth of triglycerides, which fails at high triglycerides (≥ 400 mg/dL) and increasingly underestimates LDL at low LDL levels, exactly where statin targets sit. The Martin-Hopkins method (2013) replaces the fixed 5 with a factor from a 180-cell table indexed by triglycerides and non-HDL cholesterol — this calculator uses the table’s median strata — and the NIH Sampson equation (2020) uses a fitted polynomial that stays accurate up to 800 mg/dL of triglycerides. Non-HDL cholesterol, simply total minus HDL, needs no estimate and is a strong risk marker in its own right, especially when triglycerides are high.

Worked example

Total 210, HDL 48, triglycerides 160 mg/dL: Friedewald 210 − 48 − 32 = 130; Martin-Hopkins factor 4.3 → 125; Sampson ≈ 133; non-HDL 162.

Frequently asked questions

Do I need to fast?

For Friedewald, yes — non-fasting triglycerides inflate the TG/5 term and underestimate LDL. Martin-Hopkins and Sampson tolerate non-fasting samples better; non-HDL is unaffected.

How do I convert mmol/L to mg/dL?

Multiply cholesterol by 38.67 and triglycerides by 88.57. The calculator handles both unit systems.

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Clinical decision tool for education and for use by trained clinicians alongside judgement — not a diagnosis and not a substitute for medical assessment. Scores validated in specific populations may not apply to every patient.