LDL cholesterol calculator Estimate LDL from total cholesterol, HDL, and triglycerides using Friedewald and Sampson-NIH, then compare the result with non-HDL context and formula-validity cutoffs.
Common LDL panel examples
Units
Quick reference
Friedewald uses triglycerides ÷ 5 in mg/dL and becomes unreliable above 400 mg/dL
Sampson-NIH can extend calculated LDL use further into higher triglyceride ranges
Direct LDL or clinician/lab interpretation is still preferred when triglycerides are very high
Estimated LDL
107
mg/dL LDLFriedewaldNear-optimal
Near-optimal estimated LDL using the Friedewald equation.
LDL band
mg/dL
Status
Optimal
< 100
Reference
Near-optimal
100–129
Your result
Borderline high
130–159
Reference
High
160–189
Reference
Very high
≥ 190
Reference
Formula
Estimated LDL
Use note
Friedewald
107 mg/dL
Routine panels when TG is 400 mg/dL or lower
Sampson-NIH
110 mg/dL
Useful comparison when TG is higher or LDL is already low
Lipid sheet
Entered unit
Normalized mg/dL
Total cholesterol
190 mg/dL
190 mg/dL
HDL
55 mg/dL
55 mg/dL
Triglycerides
140 mg/dL
140 mg/dL
Estimated VLDL
28 mg/dL
28 mg/dL
Non-HDL cholesterol
135 mg/dL
135 mg/dL
Primary method
Friedewald
Non-HDL cholesterol
135 mg/dL
Friedewald valid
Yes
Formula delta
3 mg/dL
Calculated LDL is only one part of risk review Use calculated LDL as one part of a full cardiovascular review that also considers non-HDL cholesterol, triglycerides, blood pressure, diabetes, smoking, and treatment targets.
LDL cholesterol calculator guide: compare Friedewald and Sampson-NIH estimates with LDL
An LDL cholesterol calculator estimates LDL-C from total cholesterol, HDL-C, and triglycerides when a direct LDL measurement is not reported.
What this LDL cholesterol calculator is doing
LDL cholesterol is often estimated from the standard lipid panel rather than measured directly. The panel gives total cholesterol, HDL cholesterol, and triglycerides. A calculator then estimates LDL by subtracting HDL and an estimated very-low-density lipoprotein cholesterol contribution from total cholesterol.
That sounds simple, but the estimate depends on the formula used. Friedewald is the classic equation and is still widely recognized. Sampson-NIH is a newer equation that can hold up better when triglycerides are higher or LDL is already low. This calculator shows both instead of forcing the user into a single hidden formula.
Friedewald equation versus Sampson-NIH
The Friedewald equation uses a fixed triglyceride divisor. In mg/dL, LDL = total cholesterol − HDL − triglycerides ÷ 5. In mmol/L, the same logic becomes a triglyceride divisor of 2.2 after conversion. This works reasonably well for many routine lipid panels, which is why Friedewald became the standard teaching formula.
The limitation is that triglyceride-rich lipoproteins do not behave as if the triglyceride-to-VLDL relationship is fixed for every patient and every triglyceride level. Sampson-NIH uses a more flexible equation and has been shown to improve classification accuracy in patients with higher triglycerides and in settings where LDL is already low. That does not make every Sampson result clinically definitive, but it does make formula choice matter.
Friedewald LDL = Total − HDL − (Triglycerides ÷ 5)
Traditional LDL estimate in mg/dL. In mmol/L, the triglyceride divisor is 2.2.
Newer NIH-derived equation used in mg/dL after conversion when needed.
When calculated LDL becomes less reliable
The classic Friedewald estimate becomes unreliable once triglycerides exceed 400 mg/dL. That threshold matters because many older calculators stop there, but real lipid panels do not. Sampson-NIH can extend calculated LDL use further into higher-triglyceride ranges, yet even then the result still needs more caution than a standard fasting panel with lower triglycerides.
Low LDL values matter too. In patients already on intensive lipid-lowering therapy, even a modest formula bias can change whether someone looks above or below a treatment threshold such as 70 mg/dL. That is one reason newer equations and direct LDL methods matter in current practice.
Friedewald is generally treated as unreliable when triglycerides are above 400 mg/dL.
Sampson-NIH can still provide an estimate in some higher-triglyceride situations, but it is not a substitute for clinician or laboratory judgment.
Very low LDL values are another setting where formula choice matters more.
Direct LDL, apoB, lipoprotein(a), and full cardiovascular risk context may be more useful than a single calculated LDL number.
Worked examples: routine panel, low LDL panel, and high triglycerides
A routine panel of total cholesterol 190 mg/dL, HDL 55 mg/dL, and triglycerides 140 mg/dL gives a Friedewald LDL of 107 mg/dL. That sits in the near-optimal band. In a panel like this, formula differences are usually modest and the bigger question is how that LDL fits with the patient’s overall cardiovascular risk.
Now consider a lower-LDL panel with total cholesterol 120 mg/dL, HDL 45 mg/dL, and triglycerides 160 mg/dL. Friedewald and Sampson may differ enough to change how close the estimate sits to lower treatment thresholds. If triglycerides rise to 450 mg/dL, Friedewald is no longer dependable and the discussion shifts toward Sampson, non-HDL, or direct LDL rather than pretending the classic estimate is still interchangeable.
Why non-HDL cholesterol belongs beside LDL
Non-HDL cholesterol equals total cholesterol minus HDL. It captures all atherogenic cholesterol particles, not just LDL. That makes it especially useful when triglycerides are elevated, because the panel may still be informative even when the LDL estimate is less stable.
This page keeps non-HDL visible for that reason. If the LDL formula becomes less trustworthy, non-HDL often remains one of the clearest anchors from the same lipid panel.
How to read LDL bands without over-reading the calculator
LDL bands such as optimal, near-optimal, borderline high, high, and very high are helpful as educational reference ranges. They make it easier to understand what the estimate means in broad terms. They do not, on their own, tell you whether medication should start, intensify, or stay the same.
That depends on the rest of the cardiovascular picture: prior ASCVD, diabetes, blood pressure, smoking, kidney disease, family history, lipoprotein(a), apoB, and clinician-set targets. The calculator can show the category; it cannot set the treatment goal.
When a direct LDL test is better
A direct LDL measurement is often the better choice when triglycerides are high, when the LDL estimate sits near a key treatment threshold, or when the lab report and the clinical picture do not seem to line up. Many clinicians will also look at apoB or non-HDL cholesterol when they want a more stable measure of atherogenic particle burden.
That is why a strong LDL calculator should not pretend every estimated LDL is equally trustworthy. The right question is not only what the formula says, but whether a formula is good enough for the panel in front of you.
What affects LDL besides the formula
Dietary saturated fat, weight change, exercise, genetics, diabetes, thyroid status, kidney disease, and lipid-lowering medication can all shift LDL. Some people improve LDL substantially with lifestyle changes. Others, especially those with familial hypercholesterolaemia or established cardiovascular disease, may need medication regardless of lifestyle quality.
That is why comparing one lab result with the next matters more than memorizing one equation. If the same person’s LDL estimate changes over time, the trend and the clinical setting often matter more than a single isolated calculator result.
What this result does not cover
This page does not replace direct LDL measurement, apoB testing, lipoprotein(a), or a clinician’s cardiovascular risk assessment. It also does not account for laboratory-method differences that can change how one equation performs against another.
Use it as an educational estimator and comparison tool, then confirm the result against the actual lab report and clinical advice when the decision matters.
The classic Friedewald formula is LDL = total cholesterol − HDL − triglycerides ÷ 5 in mg/dL. Newer equations such as Sampson-NIH use a more complex correction and can be more reliable when triglycerides are higher or LDL is already low.
What is the Friedewald equation?
It is the traditional LDL estimate used when a lipid panel reports total cholesterol, HDL, and triglycerides but not a direct LDL measurement. It assumes VLDL cholesterol can be approximated from triglycerides.
What is the Sampson-NIH LDL equation?
It is a newer LDL estimation formula that can classify LDL more accurately than Friedewald in some settings, especially when triglycerides are elevated or LDL is already low.
When is Friedewald LDL invalid?
The classic Friedewald estimate is generally treated as unreliable once triglycerides exceed 400 mg/dL. At that point, direct LDL measurement or a newer equation with clinical interpretation is preferred.
Can Sampson-NIH replace a direct LDL test?
No. It can provide a better estimate in some higher-triglyceride settings, but it is still a calculated LDL result. Direct LDL measurement and clinician/lab interpretation remain more important when the panel is difficult to estimate reliably.
Why does non-HDL cholesterol matter?
Non-HDL cholesterol captures all atherogenic cholesterol particles, not just LDL. It often stays useful even when the calculated LDL estimate becomes less dependable because triglycerides are elevated.
What is a healthy LDL level?
For many adults, below 100 mg/dL is considered optimal, while 190 mg/dL or above is considered very high. Clinical targets can be much lower in people with existing ASCVD or other high-risk features.
Can I lower LDL without medication?
Sometimes. Reducing saturated fat, increasing soluble fibre, exercising regularly, stopping smoking, and losing excess weight can lower LDL. Significant or genetically driven elevations may still require medication.
Why can two LDL calculators give different answers?
Because they may use different equations. Friedewald, Sampson-NIH, and Martin-Hopkins do not treat triglycerides and VLDL the same way, so they can diverge when triglycerides are higher or LDL is very low.
Should I trust the calculator or the lab report?
Trust the lab report and your clinician over a standalone web calculator. The calculator is useful for understanding the math and the effect of different equations, but treatment decisions should follow the actual laboratory method and clinical context.
