# LDL Cholesterol Calculator

> LDL is calculated from total cholesterol, HDL, and triglycerides when direct measurement is unavailable.

**Last updated:** September 2026
**URL:** https://bodyhealthcalculator.com/ldl-calculator
**Category:** Heart & Cardiovascular

## How it works

Friedewald: LDL = Total − HDL − TG/5. Invalid when TG >400 mg/dL.

## What is LDL cholesterol?

Low-density lipoprotein cholesterol, abbreviated LDL-C, is the cholesterol mass carried inside LDL particles.

LDL particles can enter the artery wall and contribute to atherosclerotic plaque. Genetic evidence, population studies, and randomized trials support LDL as a causal factor in atherosclerotic cardiovascular disease. Most laboratories estimate LDL-C from total cholesterol, HDL cholesterol, and triglycerides. The reported number depends on the equation and the accuracy of all three measured inputs. A calculated LDL value is an estimate, not an independent measurement of every LDL particle.

Treatment decisions use LDL-C with prior cardiovascular disease, diabetes, age, blood pressure, tobacco exposure, kidney function, family history, and other risk information. Current guidance also uses non-HDL cholesterol, apolipoprotein B, lipoprotein(a), and coronary calcium in selected situations. A calculator cannot determine treatment from LDL-C alone.

Sources: [1] [2] [3]

## The Friedewald LDL calculation

For values in mg/dL, the Friedewald equation is: LDL-C = total cholesterol minus HDL-C minus triglycerides ÷ 5.

The triglycerides ÷ 5 term estimates cholesterol carried in very-low-density lipoproteins. The equation assumes a typical relationship between triglyceride and VLDL cholesterol that does not hold in every sample. For values in mmol/L, use: LDL-C = total cholesterol minus HDL-C minus triglycerides ÷ 2.2. Do not use the divisor 5 with mmol/L values. All three inputs must come from the same blood draw and use the same unit system.

The original formula was developed from 448 people and was not intended for triglycerides at or above 400 mg/dL. Accuracy also falls as triglycerides rise below that limit and as LDL-C falls. A numerical output does not make the equation valid for an unsuitable sample.

*Friedewald equation by unit system*

| Input unit | Equation | Do not use when |
| --- | --- | --- |
| mg/dL | TC minus HDL-C minus (TG ÷ 5) | TG is 400 mg/dL or higher |
| mmol/L | TC minus HDL-C minus (TG ÷ 2.2) | TG is 4.5 mmol/L or higher |

Sources: [2] [4]

## Worked LDL calculation

Suppose total cholesterol is 220 mg/dL, HDL-C is 50 mg/dL, and triglycerides are 150 mg/dL. Estimated VLDL cholesterol is 150 ÷ 5 = 30 mg/dL. Friedewald LDL-C is 220 minus 50 minus 30 = 140 mg/dL.

The same profile in mmol/L is approximately total cholesterol 5.69, HDL-C 1.29, and triglycerides 1.69. The calculation is 5.69 minus 1.29 minus (1.69 ÷ 2.2) = 3.63 mmol/L. Small differences after conversion come from rounding the inputs. Now change only triglycerides to 350 mg/dL. Friedewald subtracts 70 mg/dL as estimated VLDL cholesterol. The estimate may understate LDL-C because the fixed relationship performs poorly with higher triglycerides.

A modern laboratory equation can produce a meaningfully different value from the same inputs.

Sources: [2] [4] [5]

## Why laboratories use newer equations

The Martin/Hopkins equation replaces the fixed triglyceride divisor with an adjustable factor based on triglyceride and non-HDL cholesterol strata. The Sampson/NIH equation uses regression terms that account for interactions among triglycerides and non-HDL cholesterol. Both estimate LDL-C after accounting for cholesterol outside LDL.

The 2026 US dyslipidemia guideline prefers Martin/Hopkins or Sampson/NIH over Friedewald after a standard lipid profile.

Their advantage is largest when triglycerides are elevated, LDL-C is low, or intensive therapy has lowered LDL-C near a treatment threshold. Laboratories should identify the method on the report. Extended equations can report estimates in some samples with triglycerides from 400 to 799 mg/dL, but uncertainty remains. In a study of 111,939 people in that range, extended Martin/Hopkins classified LDL categories more accurately than Friedewald or Sampson, yet all methods made clinically relevant errors. Severe hypertriglyceridemia needs direct clinical attention regardless of calculated LDL.

*Common LDL-C estimation approaches*

| Method | How VLDL cholesterol is handled | Main limitation |
| --- | --- | --- |
| Friedewald | TG ÷ 5 in mg/dL | Inaccurate with higher TG and lower LDL-C |
| Martin/Hopkins | Adjustable TG divisor | Requires a lookup factor; caution at very high TG |
| Sampson/NIH | Regression using TG and non-HDL-C | Complex formula; error persists at very high TG |
| Direct homogeneous assay | Chemical assay rather than calculation | Methods vary and are not fully standardized |

Sources: [1] [5] [6]

## Fasting and repeat-test context

A nonfasting lipid panel is suitable for initial assessment in most people.

Total cholesterol, HDL-C, and LDL-C usually change little after ordinary meals, while triglycerides rise more. Because triglycerides feed directly into every common LDL equation, fasting status can affect the estimate even when the true LDL particle burden is unchanged. A fasting sample is useful after a nonfasting triglyceride result above 400 mg/dL, with known hypertriglyceridemia, suspected genetic dyslipidemia, premature cardiovascular disease, or a family history of either condition. Patients with diabetes should not skip food or medicine without instructions because fasting can cause hypoglycemia.

Repeat testing is appropriate after starting or changing lipid-lowering therapy and when a result is unexpected. Guidance commonly uses a 4 to 12 week interval after a treatment change, followed by intervals based on response and adherence. Acute illness, pregnancy, thyroid disease, kidney or liver disease, large weight change, and some medicines can shift the profile.

Sources: [1] [4] [7]

## Interpreting LDL-C in clinical context

LDL-C at or above 190 mg/dL raises concern for severe primary hypercholesterolemia and possible familial hypercholesterolemia.

Clinical evaluation should confirm the value, review secondary causes, document family history, and consider family screening. A calculation alone cannot establish the genetic diagnosis. Lower treatment thresholds apply to some people with established atherosclerotic cardiovascular disease, diabetes, chronic kidney disease, or high predicted risk. Current recommendations match lipid-lowering intensity and LDL or non-HDL goals to risk. A value described as acceptable for one person may remain above goal for another.

The percentage change from a valid pretreatment baseline can be as useful as the achieved value. If LDL-C falls from 180 to 105 mg/dL, the reduction is (180 minus 105) ÷ 180 × 100 = 41.7%. Biological variation, adherence, dose timing, and equation changes should be considered before labeling treatment ineffective.

*LDL cholesterol treatment targets. ACC/AHA 2018 cholesterol guidelines (mg/dL).*

| Risk category | LDL target |
| --- | --- |
| Optimal (general population) | Below 100 mg/dL |
| Near optimal | 100 to 129 mg/dL |
| Borderline high | 130 to 159 mg/dL |
| High | 160 to 189 mg/dL |
| Very high | 190 mg/dL and above |
| High-risk patients (clinical ASCVD) | Below 70 mg/dL (or 50% reduction) |

Sources: [1] [3] [8]

## Causes of an unexpected LDL result

High LDL-C may reflect an inherited disorder, a diet high in saturated or trans fat, hypothyroidism, nephrotic syndrome, cholestatic liver disease, pregnancy, obesity, or medicines such as glucocorticoids and cyclosporine. The pattern, history, examination, and targeted tests distinguish these causes.

An unexpectedly low calculated LDL-C can result from a high triglyceride value, severe illness, malnutrition, hyperthyroidism, chronic liver disease, lipid-lowering therapy, or equation bias. Rare inherited conditions also produce low LDL. The calculator cannot separate a healthy treatment response from disease.

Dysbetalipoproteinemia, also called type III hyperlipoproteinemia, disrupts the assumed composition of remnant particles. Standard LDL equations should not be used for diagnosis in that setting. Marked discordance among LDL-C, non-HDL cholesterol, triglycerides, and apoB warrants specialist or laboratory review.

Sources: [4] [7] [9]

## Population and measurement caveats

Equation performance depends on the population and reference method used for development. Friedewald came from a small clinical sample. Martin/Hopkins used a much larger US laboratory population, while Sampson/NIH used NIH clinical samples. Validation across ages, ancestry groups, disease states, and laboratory platforms is uneven.

Children need pediatric reference and treatment pathways. Pregnancy produces expected lipid changes and requires obstetric interpretation.

People with diabetes, obesity, metabolic syndrome, or kidney disease often have triglyceride-rich particles that make LDL-C less representative of atherogenic particle number. Non-HDL cholesterol or apoB may add information. Direct LDL-C is not automatically a gold-standard answer. Routine homogeneous assays use different reagents and can disagree in dyslipidemia. Beta-quantification with ultracentrifugation is the reference method, but it is expensive and rarely available for routine care. The reported method should guide comparisons over time.

Sources: [1] [4] [6] [10]

## Limitations of calculated LDL-C

All equations inherit measurement error from total cholesterol, HDL-C, and triglycerides.

Friedewald further assumes a fixed triglyceride to VLDL cholesterol relationship. Modern equations reduce average error but cannot identify the exact LDL-C of every individual, particularly when triglyceride metabolism is abnormal. LDL-C measures cholesterol mass, not LDL particle count, plaque burden, inflammation, or current artery narrowing. Two people with the same LDL-C can have different apoB concentrations and different absolute cardiovascular risk. A low LDL-C does not cancel smoking, hypertension, diabetes, or elevated lipoprotein(a).

Categories can create false certainty near a boundary. A calculated value of 99 mg/dL is not biologically distinct from 101 mg/dL. Clinicians consider assay variation, trend, treatment indication, baseline risk, and the consequence of misclassification before acting.

Sources: [1] [4] [5] [6]

## When clinical confirmation is required

Arrange clinical confirmation for LDL-C at or above 190 mg/dL, triglycerides at or above 500 mg/dL, a possible inherited disorder, premature cardiovascular disease, or a major unexplained change.

Confirmation can include a repeat fasting panel, review of the estimation method, secondary-cause testing, and family history. People with known cardiovascular disease, diabetes, chronic kidney disease, pregnancy, childhood dyslipidemia, or current lipid medicine need individualized targets and follow-up. Seek urgent care for chest pressure, sudden weakness, speech difficulty, or severe abdominal pain. Recalculating LDL-C does not evaluate those symptoms.

Lifestyle changes should follow evidence-based cardiovascular prevention goals. Replace saturated fat with unsaturated fat, avoid trans fat, choose soluble-fiber foods, maintain physical activity, and avoid tobacco. Medication decisions require a clinician because expected benefit depends on baseline risk, contraindications, adverse effects, and the LDL reduction needed.

Sources: [1] [3] [7] [8]

## FAQ

### What LDL level is optimal?

Below 100 mg/dL is optimal for most. High-risk patients may target below 70 mg/dL.

## References

1. ACC and AHA Joint Committee on Clinical Practice Guidelines. [2026 Guideline on the Management of Dyslipidemia](https://www.jacc.org/doi/10.1016/j.jacc.2025.11.016)
2. Friedewald, Levy, and Fredrickson. [Estimation of the Concentration of LDL Cholesterol in Plasma](https://pubmed.ncbi.nlm.nih.gov/4337382/)
3. National Heart, Lung, and Blood Institute. [Blood Cholesterol](https://www.nhlbi.nih.gov/health/blood-cholesterol)
4. Association for Diagnostics and Laboratory Medicine. [Guidance on the Measurement and Reporting of Lipids and Lipoproteins](https://doi.org/10.1093/jalm/jfae057)
5. Martin et al.. [Comparison of a Novel Method Versus the Friedewald Equation for Estimating LDL-C](https://pubmed.ncbi.nlm.nih.gov/24240933/)
6. Sampson et al.. [A New Equation for Calculation of LDL-C in Patients With Normolipidemia or Hypertriglyceridemia](https://pubmed.ncbi.nlm.nih.gov/32101259/)
7. CDC. [About Cholesterol](https://www.cdc.gov/cholesterol/about/index.html)
8. American Diabetes Association. [Standards of Care in Diabetes: Cardiovascular Disease and Risk Management](https://diabetesjournals.org/care/article/49/Supplement_1/S216/163943/10-Cardiovascular-Disease-and-Risk-Management)
9. Feingold et al.. [The Measurement of Lipids and Lipoproteins for Diagnosis and Treatment](https://www.ncbi.nlm.nih.gov/books/NBK355892/)
10. Sajja et al.. [Comparison of LDL-C Estimation Methods at High Triglyceride Levels](https://pubmed.ncbi.nlm.nih.gov/34709388/)

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