LDL Calculator
With total cholesterol 200 mg/dL, hdl cholesterol 50 mg/dL, triglycerides 150 mg/dL, ldl comes to 120 mg/dL — ldl, friedewald. It is reached in 8 steps, the last of which is 150 - 30, and each one is printed on the page with its numbers filled in. The formula is the one published by Friedewald et al., not an approximation fitted to it.
LDL cholesterol calculated from a lipid panel by both Friedewald and the Martin-Hopkins method, which disagree most where it matters.
Formula and sources checked · How we check
Total cholesterol 200 mg/dL, HDL cholesterol 50 mg/dL, Triglycerides 150 mg/dL
120 mg/dL
LDL, Friedewald for the example below. Editing a field recomputes the calculator below; this figure holds the answer the page was loaded with.
It is written into the HTML rather than drawn by a script, so a search engine reading this page without running JavaScript still finds an answer.
- Non-HDL cholesterol
200 - 50150 mg/dL- VLDL by the fixed factor of 5
150 / 530 mg/dL- LDL, Friedewald
150 - 30120 mg/dL- Martin-Hopkins divisor for this panel
(5.4)5.4- LDL, Martin-Hopkins
150 - 150 / 5.4122.222 mg/dL- How far the two methods differ
122.22222 - 1202.222 mg/dL- Total to HDL ratio
200 / 504- Friedewald LDL in mmol/L
120 / 38.673.103 mmol/L
Worked example
Total 200, HDL 50, triglycerides 150 gives non-HDL of 150. Friedewald divides the triglycerides by a fixed 5 for a VLDL of 30 and an LDL of 120. Martin-Hopkins picks the divisor from the panel itself — 5.4 here — for an LDL of 122. Two points apart at this panel, and far further apart when triglycerides are high and LDL is low.
How to work it out yourself
- 1.Subtract HDL from total cholesterol. That is non-HDL, and it needs no estimate at all.
- 2.Friedewald estimates VLDL as triglycerides over 5, then subtracts it from non-HDL.
- 3.Martin-Hopkins replaces the fixed 5 with a divisor read from a table of triglyceride and non-HDL bands — 5.4 for this panel.
- 4.Compare the two. Where they disagree, the disagreement itself is the finding.
The formula
- Non-HDL cholesterol
200 - 50 - VLDL by the fixed factor of 5
150 / 5 - LDL, Friedewald
150 - 30 - Martin-Hopkins divisor for this panel
(5.4) - LDL, Martin-Hopkins
150 - 150 / 5.4 - How far the two methods differ
122.22222 - 120 - Total to HDL ratio
200 / 50 - Friedewald LDL in mmol/L
120 / 38.67
Source: Friedewald et al. — Estimation of LDL cholesterol without preparative ultracentrifuge, Clin Chem 1972, Martin et al. — Comparison of a novel method vs the Friedewald equation, JAMA 2013
Questions people actually ask
- What is the Friedewald equation?
- LDL = total cholesterol − HDL − triglycerides/5, published in 1972. The division by 5 assumes a fixed ratio of triglycerides to VLDL cholesterol that holds on average and fails at the edges, which is the whole reason a replacement exists.
- When is Friedewald wrong?
- Above 400 mg/dL of triglycerides it is not valid at all, and most laboratories will not report it. Below 70 mg/dL of LDL it systematically underestimates — by enough to move a patient across a treatment threshold, which is what the 2013 JAMA analysis of 1.3 million panels showed and why Martin-Hopkins exists.
- What is the difference between calculated and direct LDL?
- Calculated LDL is arithmetic on three other numbers; direct LDL is measured. Panels report the calculated figure because it is free, and it is close enough for most people. Where triglycerides are high, LDL is very low, or the patient is not fasting, the direct measurement is the one to ask for.
- Why is non-HDL cholesterol worth looking at?
- Because it is measured rather than estimated — total minus HDL, no assumption in it — and it captures every atherogenic particle rather than only LDL. Guidelines increasingly use it as a secondary target for exactly that reason, and it is unaffected by whether the patient fasted.
- Does the patient need to fast?
- For a Friedewald calculation, usually yes, because a recent meal raises triglycerides and every point of that is divided by 5 and taken off the LDL. Non-HDL and direct LDL are much less affected, which is part of why non-fasting panels have become acceptable.
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