LDL Calculator

How to use this calculator

1. Match the unit toggle to your lab printout. US labs report mg/dL. The UK, most of Europe, Canada, and Australia report mmol/L. Switching converts every input and every result on the fly.
2. Enter the three numbers every lipid panel reports. Total cholesterol, HDL, and triglycerides. You do not need an LDL value — producing one is the point.
3. Pick your risk context. This is the step other calculators skip. The same LDL number means something different depending on whether you are being screened routinely or have already had a heart attack, because the goal moves from 100 down to 55 mg/dL.
4. Read both estimates, not one. Friedewald and Sampson-NIH are both legitimate published equations. When they land on opposite sides of your goal line, the tool says so explicitly.
5. Check the non-HDL number. It requires no equation at all, so it cannot be wrong in the way a calculated LDL can. When the two LDL estimates argue, non-HDL is the tiebreaker your clinician will reach for.

Why this calculator is different from other LDL calculators

Every LDL calculator ranking for this search shows one equation. The busiest one shows Friedewald. A well-known consumer calculator shows Friedewald and describes limitations it does not actually have. One page titled after the Sampson equation prints the Friedewald formula underneath it. None of them mention that a different equation, applied to the identical blood panel, can move you from "at goal" to "not at goal."

• Two equations, computed together, given equal weight. Neither is presented as the "real" answer, because neither is. Friedewald (1972) is what most labs still print. Sampson-NIH (2020) was built specifically for the panels Friedewald handles worst.
• A disagreement engine, not just two numbers. The tool compares both estimates against the goal you selected and calls out the case that matters: when one says you are at goal and the other says you are not. That is the only situation where the choice of equation changes what happens next.
• A goal track you can read at a glance. Both estimates are plotted as dots against your goal line. When the dots sit on opposite sides of it, you see the problem before you read a word.
• Risk context changes the interpretation, not just the wording. Four contexts, four goals: 100, 100, 70, and 55 mg/dL, with matching non-HDL goals of 130, 130, 100, and 85.
• Validity limits are enforced, not mentioned in a footnote. Above 400 mg/dL of triglycerides, Friedewald is suppressed rather than displayed with a warning. Above 800, so is Sampson-NIH. A number you should not act on is worse than no number.
• The math is auditable and runs on your device. Every formula is printed below with its citation, and the implementation is checked against a fixture suite on every build. Nothing you type is sent anywhere.
• Reviewed by a named clinician. Dr. David Taylor, MD, PhD, with sources cited for every equation and every threshold.

How this calculator works (the math)

All arithmetic runs in mg/dL and converts for display, because the Sampson-NIH equation is only defined in mg/dL. Keeping one internal unit is what lets the two equations be compared directly.

Friedewald equation (1972)

The original, and still the most widely printed:

LDL-C = Total cholesterol − HDL-C − (Triglycerides / 5)

Per Friedewald, Levy & Fredrickson, Clin Chem 1972;18(6):499–502. It assumes a fixed ratio of triglycerides to VLDL cholesterol of 5:1. That assumption holds reasonably well in the middle of the range and breaks down at the edges, which is where its two known failure modes live: it is unreliable above 400 mg/dL of triglycerides, and it systematically underestimates LDL when LDL is low and triglycerides are high. That combination describes a great many people already on statin therapy.

Sampson-NIH equation, also called NIH equation 2 (2020)

Derived at the NIH against ultracentrifugation-measured LDL, specifically to fix the low-LDL and high-triglyceride cases:

LDL-C = TC/0.948 − HDL-C/0.971 − (TG/8.56 + TG × non-HDL-C/2140 − TG²/16100) − 9.44

Per Sampson M, et al. JAMA Cardiol 2020;5(5):540–548. It stays valid up to 800 mg/dL of triglycerides, double Friedewald's ceiling.

Non-HDL cholesterol

Non-HDL-C = Total cholesterol − HDL-C

No equation, no assumption, no failure mode. It captures every atherogenic particle rather than LDL alone, which is why the AHA/ACC treats it as the preferred secondary target. When two calculated LDL values disagree, this is the number that does not.

The equation this calculator does not compute, and why

You will see the Martin-Hopkins equation referenced on lab reports and in guidelines, and it is more accurate than either equation above. The 2026 national dyslipidemia guideline recommends it preferentially. It has the same shape as Friedewald but replaces the fixed divisor of 5 with an adjustable factor — somewhere between 3 and 12 — selected from a 180-cell table of median triglyceride-to-VLDL ratios stratified by triglycerides and non-HDL-C (Martin SS, et al. JAMA 2013;310(19):2061–2068).

That table was published as a figure, not as machine-readable data. Reproducing 180 clinical constants by eye is exactly the kind of shortcut that puts a quietly wrong number in front of someone making a treatment decision, so this calculator does not do it. If your lab reports a Martin-Hopkins LDL, use it — and note that where it differs from Friedewald, it almost always differs in the same direction Sampson-NIH does here, which is upward. In July 2026 the Johns Hopkins group published a simplified closed-form version designed for open adoption by laboratories (Park J, Fan L, Marzinke MA, Martin SS, JAMA Cardiology, doi:10.1001/jamacardio.2026.2314); this tool will add it at the next review.

Three worked examples

When the equations agree, and the answer is easy

Marcus is 48, no diabetes, no cardiovascular history. His panel: total cholesterol 200, HDL 50, triglycerides 150 mg/dL. Friedewald returns 120. Sampson-NIH returns 123.4. Non-HDL is 150. Both estimates sit above the 100 mg/dL general-screening goal and both land in the same "near optimal" category, so the choice of equation is irrelevant to what happens next. The conversation with his physician is about diet and activity, and a repeat panel in a year. A psyllium-based fiber supplement is the cheapest lever available to him and moves LDL 5 to 10 percent in most adults.

When the equations disagree, and it changes the conversation

Robert is 62 and had a stent placed two years ago, so he is in the "established heart disease" context with a goal of 70 mg/dL. His on-statin panel: total cholesterol 165, HDL 45, triglycerides 300 mg/dL. Friedewald returns 60.0. Sampson-NIH returns 72.0. Same blood draw, 12 mg/dL apart, sitting on opposite sides of his goal.

If his lab prints the Friedewald number, Robert is comfortably at target and nothing changes. If it prints Sampson-NIH, he is not, and adding ezetimibe or a PCSK9 inhibitor is back on the table. This is not a hypothetical: elevated triglycerides with a low LDL is precisely the profile where Friedewald is documented to read low, and it is common in statin-treated adults because statins move LDL far more than they move triglycerides. Robert's tiebreaker is his non-HDL of 120 against a goal of 100 — above goal, which supports the higher reading. CoQ10 also comes up frequently in statin users; the evidence for symptomatic benefit is mixed but the downside is low.

When neither equation should be used

Priya's panel comes back with triglycerides of 500 mg/dL, total cholesterol 220, HDL 35. Friedewald is suppressed — 500 is past its 400 mg/dL validity ceiling, and a number it produces there is not a rough estimate but an unreliable one. Sampson-NIH still applies and returns 100.5. Her non-HDL is 185, well above any goal. The honest next step is a direct LDL-C measurement, and a conversation about the triglycerides themselves, which at that level carry their own risk independent of LDL.

LDL cholesterol reference ranges

General categories, per the long-standing NCEP ATP III framework that most lab reports still print alongside your result:

• Under 100 mg/dL (2.6 mmol/L): Optimal
• 100–129 mg/dL (2.6–3.3 mmol/L): Near optimal
• 130–159 mg/dL (3.4–4.1 mmol/L): Borderline high
• 160–189 mg/dL (4.1–4.9 mmol/L): High
• 190 mg/dL (4.9 mmol/L) and above: Very high

Risk-based treatment goals, which are what the calculator's risk selector applies:

• General screening: LDL under 100, non-HDL under 130 mg/dL
• Diabetes, chronic kidney disease, or elevated 10-year risk: LDL under 100, non-HDL under 130 mg/dL
• Established cardiovascular disease: LDL under 70, non-HDL under 100 mg/dL
• Very high risk (multiple events, or one event plus multiple high-risk conditions): LDL under 55, non-HDL under 85 mg/dL

Frequently asked questions

How do you calculate LDL cholesterol?

LDL is almost never measured directly on a routine panel — it is calculated from the three values that are measured. The classic Friedewald equation subtracts HDL and one-fifth of your triglycerides from total cholesterol. The newer Sampson-NIH equation uses a more elaborate formula that corrects for the fact that the triglyceride-to-VLDL relationship is not actually a fixed 5:1 ratio. This calculator runs both so you can see the difference for your own panel.

Why is my calculated LDL different from my lab's number?

Almost certainly because your lab uses a different equation than the one you compared against. US labs are actively migrating from Friedewald to Martin-Hopkins, and some use Sampson-NIH. Differences of 5 to 15 mg/dL between equations are routine on the same blood draw, and they get larger as triglycerides rise and LDL falls. A difference is not an error in either number.

What is the difference between LDL and calculated LDL?

A direct LDL-C measurement uses a laboratory assay to measure the cholesterol carried on LDL particles. Calculated LDL infers it arithmetically from total cholesterol, HDL, and triglycerides. Calculation is standard because it is free and works well for most panels; direct measurement is ordered when triglycerides are high, when LDL is very low, or when a treatment decision sits right on a threshold. If your two estimates here disagree across your goal, that last case is you.

Do I need to fast before the blood test?

Fasting matters more for calculated LDL than for measured lipids, because eating raises triglycerides and triglycerides are an input to both equations. Current guidance allows non-fasting panels for routine screening, but if your triglycerides come back high on a non-fasting sample, a repeat fasting panel is usually the next step before anyone acts on the LDL number derived from it.

Can I embed this tool on my own site?

Yes — copy the snippet at the bottom of this page. It is free for clinicians, registered dietitians, cardiac rehabilitation programs, nursing schools, and health blogs. Attribution is built into the embed. No fee, no signup, and no analytics attached to the embedded version.

Related tools

• Cholesterol Ratio Calculator — the companion to this one. This tool produces an LDL value; that one takes LDL as an input and returns five risk ratios including TC/HDL and the Atherogenic Index of Plasma.
• Lean Body Mass Calculator — body composition drives the insulin resistance behind high triglycerides.
• Steps to Miles Calculator — aerobic activity is the most reliable lever for raising HDL.
• Blood Pressure Log — lipids and blood pressure are tracked together for a reason.
• Browse all free tools by Dr. Taylor →

Dr. Taylor's recommendations alongside a lipid panel

Three categories cover most of what is worth considering while you work on an LDL number. Each links to the full review with current picks and trade-offs:

• Best Fiber Supplements — soluble fiber, psyllium in particular, lowers LDL by 5 to 10 percent in adults with elevated cholesterol. The cheapest and lowest-risk intervention in the entire lipid toolkit, and the first thing to try before medication enters the conversation.
• Best CoQ10 Supplements — statins inhibit the same enzyme pathway that produces endogenous CoQ10, so depletion is real even though the evidence on relieving statin-associated muscle aches is mixed. Worth raising with your clinician if you are on a statin and aching.
• Best Blood Pressure Monitors — LDL and blood pressure are the two modifiable numbers that determine cardiovascular risk together. If you are tracking one at home, track both. Pair it with the technique guide so the readings are worth recording.

Sources & methodology

• Friedewald WT, Levy RI, Fredrickson DS. Estimation of the concentration of low-density lipoprotein cholesterol in plasma, without use of the preparative ultracentrifuge. Clin Chem 1972;18(6):499–502 — the Friedewald equation and its 400 mg/dL triglyceride limit.
• Sampson M, Ling C, Sun Q, et al. A new equation for calculation of low-density lipoprotein cholesterol in patients with normolipidemia and/or hypertriglyceridemia. JAMA Cardiol 2020;5(5):540–548 — the Sampson-NIH equation (NIH equation 2), valid to 800 mg/dL.
• Martin SS, Blaha MJ, Elshazly MB, et al. Comparison of a novel method vs the Friedewald equation for estimating low-density lipoprotein cholesterol levels from the standard lipid profile. JAMA 2013;310(19):2061–2068 — the Martin-Hopkins 180-cell adjustable factor.
• Park J, Fan L, Marzinke MA, Martin SS, et al. Development and validation of a simplified Martin-Hopkins LDL-C equation using machine learning. JAMA Cardiology, published online July 15, 2026. doi:10.1001/jamacardio.2026.2314.
• Grundy SM, Stone NJ, Bailey AL, et al. 2018 AHA/ACC Guideline on the Management of Blood Cholesterol. Circulation 2019;139:e1082–e1143 — non-HDL-C targets and risk-based LDL goals.
• Third Report of the NCEP Expert Panel (ATP III). JAMA 2001;285(19):2486–2497 — the general LDL-C category bands.

Implementation is verified on every build against a fixture suite whose Sampson-NIH expectations were cross-checked value-by-value against MDCalc's independent implementation. Reviewed annually, and sooner if goal thresholds change. About Dr. Taylor · Last reviewed August 21, 2026.

Embed this tool on your site

Free for clinicians, registered dietitians, cardiac rehabilitation programs, nursing and medical schools, and personal health blogs. Attribution is included in the snippet. No fee, no signup, no analytics attached to the embed.

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