LDL Cholesterol Calculator
Estimate LDL cholesterol with the equations current guidelines actually prefer, and see how far they disagree on the same blood sample.
LDL Cholesterol Calculator
Results recalculate instantly on every keystroke. Nothing you type is transmitted.
What this result does not account for
- Every figure here is an estimate; none is a direct measurement of LDL particles.
- Martin-Hopkins, the guideline-preferred method, is named but deliberately not computed.
- Equations assume a fasting sample; non-fasting panels shift triglycerides and therefore LDL.
In short: With total cholesterol 213, HDL 48 and triglycerides 180 mg/dL, Friedewald gives an LDL of 129.0 while the Sampson-NIH equation gives 132.9 — the same sample landing on opposite sides of the 130 mg/dL threshold.
Formula
LDL is almost never measured directly. Every figure on a standard lipid panel is an estimate, and the equations disagree most exactly where the stakes are highest.
Worked Example
- Find non-HDL first. 213 − 48 = 165 mg/dL. This needs no equation and is not disturbed by triglycerides.
- Apply Friedewald. 213 − 48 − 180÷5 = 129.0 mg/dL — the historic method, still what most laboratories report.
- Apply Sampson-NIH. The closed-form NIH equation gives 132.9 mg/dL on the same sample.
- Notice the threshold. 129.0 is below 130; 132.9 is above it. Two validated equations, opposite sides of a treatment line.
- Check Friedewald's validity. At 180 mg/dL triglycerides it is inside its range but already in the zone where guidelines prefer the newer equations.
The reason this page shows three equations rather than one is visible in the defaults: Friedewald says 129.0 and Sampson says 132.9, which places the same blood sample on opposite sides of the 130 mg/dL mark. The gap widens exactly where it matters most — at high triglycerides and low LDL, Friedewald systematically underestimates, so the patients at highest risk are the ones most likely to be told they have reached a goal they have not reached. A worked case: total cholesterol 140, HDL 35, triglycerides 350 gives Friedewald 35.0 against Sampson 51.7, a 16.7 mg/dL underestimate straddling the tightest secondary-prevention target. That is the clinical reason the guidelines moved.
Strengths & Limits Of This Model
Where this engine is strong
- Implements three published equations exactly, and shows where they disagree.
- Flags explicitly when Friedewald is outside its validated range.
- Reports non-HDL, which requires no equation and no triglyceride assumption.
Where it stops
- Cannot compute Martin-Hopkins without fabricating its lookup table.
- Cannot assess overall cardiovascular risk, which is what actually drives treatment.
Practical Use Cases
Reading a lipid panel that reports only Friedewald
Most laboratories still do. Compare against the Sampson figure, especially if triglycerides exceed 150 mg/dL.
Checking whether you have actually reached an LDL goal
If the two equations straddle your target, the answer is genuinely uncertain and worth raising with your clinician.
Interpreting a panel with high triglycerides
Above 400 mg/dL Friedewald is invalid outright. Understand the wider picture with the Total Cholesterol Calculator.
Using non-HDL when the estimates disagree
It needs no equation at all. The Cholesterol Ratio Calculator works it against the comparative measures.
Methodology & Editorial Standards
LDL cholesterol is rarely measured directly on a routine panel; it is estimated from total cholesterol, HDL and triglycerides, and the choice of estimating equation materially changes the answer. This engine implements three published closed-form equations exactly as specified. Friedewald, from 1972, subtracts HDL and one fifth of triglycerides from the total, assuming a fixed triglyceride-to-VLDL ratio; that assumption fails as triglycerides rise, and the equation is not valid at all above 400 mg/dL. Sampson-NIH, from 2020, replaces the fixed ratio with a fitted polynomial and performs substantially better at high triglycerides and low LDL. The 2025 modified Sampson equation further reduces bias at very low LDL, where treatment decisions are tightest. Current guidance prefers the Martin-Hopkins and Sampson-NIH equations over Friedewald, and this engine deliberately does not attempt Martin-Hopkins: it depends on a 180-cell lookup table of strata-specific median ratios that cannot be reproduced faithfully from secondary sources, and fabricating coefficients for a clinical equation would be indefensible. The engine reports the spread between the methods, flags any treatment threshold the estimates straddle, and reports non-HDL cholesterol, which requires no equation and no assumption about triglycerides at all. This calculator is an educational estimate and is not medical advice, diagnosis or treatment. Lipid and blood pressure values are interpreted in the context of overall cardiovascular risk, family history, diabetes, kidney function and medication, none of which a calculator can assess. Do not start, stop or change any medication on the basis of a figure produced here. Discuss results with a clinician, who will consider a full risk assessment rather than any single number. The engine implements the standard published formula for this calculation. Inputs are validated for domain and sign before evaluation, and any undefined case returns an em-dash rather than a spurious value.
Computation runs in IEEE-754 double precision at full internal precision; rounding to two decimal places occurs strictly at the display layer, so no cumulative drift enters the result. All monetary outputs use accounting presentation — grouped thousands, two decimals, negatives in parentheses — so figures can be transcribed directly into a model or working paper. Division-by-zero and out-of-domain inputs return an em-dash rather than a misleading number.
This engine was reconciled against an independent reference implementation and hand-verified for the worked example above before release. Our full five-stage review process is published on the About Us page.
Disclaimer. This calculator is provided for informational and modelling purposes only and does not constitute financial, tax, legal, medical, or engineering advice. Verify all figures with a qualified professional before acting on them.
LDL Cholesterol Calculator — 20 Expert FAQs
20 analyst-written answers to the questions practitioners actually ask — optimised for voice and answer-engine retrieval.
How is LDL cholesterol calculated?
Usually by Friedewald: total cholesterol minus HDL minus triglycerides divided by five. Here that gives 129.0 mg/dL.
Why do different calculators give different LDL values?
Because they use different equations. Friedewald gives 129.0 here and Sampson-NIH gives 132.9 on the same sample.
Which LDL equation is most accurate?
Martin-Hopkins, at roughly 90% correct treatment classification, then Sampson-NIH at about 86% and Friedewald at about 83%.
Why does this calculator not compute Martin-Hopkins?
It needs a 180-cell lookup table that cannot be reproduced faithfully. Inventing coefficients for a clinical equation would be indefensible.
When is Friedewald invalid?
At triglycerides of 400 mg/dL or above, outright. Above 150 mg/dL guidelines already prefer the newer equations.
Does Friedewald over- or underestimate?
It underestimates, and does so most at low LDL with high triglycerides — exactly the highest-risk patients.
What is non-HDL cholesterol?
Total cholesterol minus HDL — 165 mg/dL here. It captures every atherogenic particle and needs no equation at all.
Should I fast before a lipid panel?
Increasingly not required for screening. Fasting matters most when triglycerides are high or an equation-based LDL is needed.
What is a good LDL level?
It depends entirely on your overall risk. Goals commonly run below 100, below 70, or below 55 mg/dL for progressively higher risk.
What does 130 mg/dL mean?
It is a conventional band boundary, not a cliff. Risk is continuous, which is why two equations straddling it matters less than the trend.
Can I convert to mmol/L?
Divide cholesterol by 38.67 and triglycerides by 88.57. Note the mmol/L Friedewald uses a divisor of 2.2, not 5.
Why is my LDL different from last time?
Biological variation alone runs several percent between draws, before diet, illness or a different laboratory method are considered.
Is direct LDL measurement better?
It avoids the equation entirely but direct assays vary in standardisation and cost more, so they are not routine.
Does a high LDL always need medication?
No. Treatment depends on total cardiovascular risk, not one number, and lifestyle change is the first step for most people.
What lowers LDL most?
Reducing saturated fat, losing excess weight and increasing soluble fibre, with statins the most effective pharmacological option.
Does the equation matter if my triglycerides are normal?
Much less. Below 150 mg/dL all three equations usually agree closely and the choice rarely changes a decision.
Is this ldl cholesterol calculator free to use?
Yes. It is free, requires no account, and has no usage limits. ApexConverter is funded by contextual advertising, never by selling user data.
Is my data sent to a server?
No. The engine runs as Vanilla JavaScript inside your browser under our Zero-Server Client-Side Execution model. Your figures are computed locally and are never transmitted, logged, or stored.
How accurate is this calculator?
It applies the standard closed-form formula in IEEE-754 double precision, rounding only at the display layer. The engine is reconciled against an independent reference implementation before release.
Does it work on mobile?
Yes. The interface is mobile-first with numeric keypad hints and is tested down to a 320-pixel viewport with no horizontal scrolling.