LDL Cholesterol Calculator

Calculate your LDL (bad cholesterol) using the Friedewald formula

Select Unit

Total Cholesterol TC

Normal: < 200 mg/dL

HDL Cholesterol (Good Cholesterol)

Normal: ≥ 40 mg/dL

Triglycerides

Normal: < 150 mg/dL

Frequently Asked Questions (FAQ)

Why is LDL called "bad cholesterol"?

LDL is called "bad cholesterol" because: (1) It contributes to atherosclerosis by depositing in arterial walls; (2) It triggers inflammation, attracting immune cells to form plaques; (3) It causes vascular narrowing as plaques grow; (4) It can lead to thrombosis when plaques rupture, causing heart attacks or strokes; (5) There is a dose-response relationship - higher LDL levels mean higher cardiovascular risk. In contrast, HDL can remove cholesterol from arterial walls and is therefore called "good cholesterol".

How can I lower my LDL cholesterol?

Lowering LDL cholesterol requires comprehensive management: Lifestyle changes: (1) Diet: Reduce saturated and trans fats, increase dietary fiber; (2) Exercise: At least 150 minutes of moderate-intensity aerobic exercise per week; (3) Weight: Weight loss can lower LDL; (4) Smoking cessation: Quitting improves lipid profile. Medications: (1) Statins: First-line drugs, can lower LDL by 25-50%; (2) Ezetimibe: Adjunctive therapy for further LDL reduction; (3) PCSK9 inhibitors: Potent lipid-lowering drugs; (4) Bile acid sequestrants: Older lipid-lowering drugs. Treatment should be guided by a physician based on individual risk.

When should LDL be measured directly instead of using the formula?

Direct LDL measurement should be performed in these situations: (1) Triglycerides > 400 mg/dL (4.52 mmol/L); (2) Type III hyperlipidemia (familial dysbetalipoproteinemia); (3) Poor fasting status or non-fasting state; (4) When accurate LDL assessment is needed (such as treatment monitoring); (5) Other conditions affecting formula accuracy. Direct LDL measurement (such as homogeneous method or ultracentrifugation) is more accurate but more expensive, not suitable for routine screening.

Do cholesterol tests require fasting?

Traditionally, 8-12 hours of fasting was required before lipid testing because eating affects triglyceride levels. However, the latest guidelines suggest: (1) Non-fasting testing is acceptable for routine screening; (2) LDL calculation may be less accurate when triglycerides are elevated in non-fasting state; (3) Triglycerides increase significantly in non-fasting state; (4) Total cholesterol and HDL are less affected by eating. Recommendation: If using Friedewald formula to calculate LDL, fasting testing is preferred. If LDL is measured directly, non-fasting testing is also acceptable.

How low should LDL be lowered?

LDL target values should be determined based on cardiovascular risk stratification: (1) Very high risk: LDL < 70 mg/dL (1.81 mmol/L), or even < 55 mg/dL (1.42 mmol/L); (2) High risk: LDL < 100 mg/dL (2.59 mmol/L); (3) Moderate risk: LDL < 130 mg/dL (3.36 mmol/L); (4) Low risk: LDL < 160 mg/dL (4.14 mmol/L). "Lower is better"? For very high-risk patients, studies show that lowering LDL to 50 mg/dL or even lower is safe and can further reduce cardiovascular event risk. However, target values should be determined by physicians based on individual patient circumstances.

What are the limitations of the Friedewald formula?

The Friedewald formula has several important limitations: (1) High triglycerides: Formula is inaccurate when TG > 400 mg/dL (4.52 mmol/L); (2) Type III hyperlipidemia: Formula does not apply to these patients; (3) Non-fasting status: Ideally should be measured after 12 hours fasting; (4) Estimation nature: This is an empirical formula, direct measurement is more accurate; (5) Individual variation: The formula assumes a fixed ratio, but actual VLDL composition varies. For accurate clinical decision-making, especially when triglycerides are elevated, direct LDL measurement is recommended.

Medical Disclaimer

This calculator provides results for reference only and cannot replace professional medical diagnosis. LDL cholesterol assessment should be performed by healthcare professionals. The calculator uses the Friedewald formula which has limitations and may not be accurate for all individuals. Consult your doctor for proper cholesterol assessment and treatment decisions.

Most standard lipid panels measure total cholesterol, HDL cholesterol, and triglycerides directly, then calculate LDL cholesterol from those three numbers rather than measuring it directly in the lab. This calculator applies the Friedewald equation, the formula labs have used since 1972, to estimate LDL cholesterol in mg/dL or mmol/L, and flags when the result is likely to be unreliable.

The formula

LDL = Total cholesterol - HDL - (Triglycerides / 5), in mg/dL; LDL = Total cholesterol - HDL - (Triglycerides / 2.2), in mmol/L

Total cholesterol, HDL, and triglycerides are all measured from the same fasting blood sample
Triglycerides divided by 5 (mg/dL) or by 2.2 (mmol/L) estimates VLDL cholesterol from the triglyceride level

Friedewald WT, Levy RI, Fredrickson DS. Clinical Chemistry, 1972

How the calculation works

A lipid panel directly measures total cholesterol, HDL cholesterol, and triglycerides. Directly measuring LDL cholesterol requires an additional, more expensive laboratory step called ultracentrifugation, so in routine practice it is instead estimated from the three measured values. The Friedewald equation does this by subtracting HDL cholesterol and an estimate of VLDL cholesterol from total cholesterol.

The equation estimates VLDL cholesterol as triglycerides divided by 5 in mg/dL, or by 2.2 in mmol/L, based on the typical ratio of triglyceride to cholesterol content inside VLDL particles. That ratio is reasonably stable at normal triglyceride levels but becomes progressively less accurate as triglycerides rise, which is why the equation is considered unreliable above a triglyceride threshold rather than being universally applicable.

How to read your result

These categories follow the cut points long used in US cholesterol guidance. They describe population risk categories, not a personal treatment target, which a clinician sets based on overall cardiovascular risk rather than LDL alone.

General population, no other risk factors: optimal LDL is below 100 mg/dL (2.6 mmol/L)
Known cardiovascular disease (secondary prevention): a commonly used target is below 70 mg/dL (1.8 mmol/L)
Very high risk, such as a recent acute coronary event or cardiovascular disease combined with diabetes: some guidelines, including the 2019 ESC/EAS guideline, set a lower target of below 55 mg/dL (1.4 mmol/L)
These are illustrative treatment thresholds drawn from major guidelines, not a substitute for an individualized target set with a clinician

LDL cholesterol (mg/dL)	LDL cholesterol (mmol/L)	Category
Below 100	Below 2.6	Optimal
100-129	2.6-3.3	Near optimal
130-159	3.4-4.1	Borderline high
160-189	4.1-4.9	High
190 and above	4.9 and above	Very high

When the Friedewald estimate breaks down

The Friedewald equation is not valid when triglycerides exceed 400 mg/dL (about 4.5 mmol/L). At that level, the fixed triglyceride-to-VLDL-cholesterol ratio the formula assumes no longer holds, and the calculation can understate or overstate LDL cholesterol substantially. Some laboratories will report calculated LDL as invalid or omit it entirely once triglycerides cross this threshold, and a directly measured LDL, or a non-HDL cholesterol figure, is used instead.

A newer method, the Martin-Hopkins equation published in 2013, replaces the fixed divisor of 5 with a variable factor selected from a large reference table based on a person's own triglyceride and non-HDL cholesterol levels. It performs better than the Friedewald equation at both high triglycerides and low LDL cholesterol, and a growing number of laboratories now report it instead of, or alongside, the Friedewald estimate.

Non-HDL cholesterol as an alternative

Non-HDL cholesterol, calculated simply as total cholesterol minus HDL cholesterol, captures every atherogenic particle class in one number, including LDL, VLDL and VLDL remnants, and intermediate-density lipoprotein, without relying on the triglyceride-based estimate the Friedewald equation needs. Because it needs no triglyceride term, non-HDL cholesterol stays reliable even above the 400 mg/dL triglyceride threshold where calculated LDL breaks down, and 2018 ACC/AHA cholesterol guidance recommends it as a routine secondary target alongside LDL, particularly for people with diabetes, obesity, or elevated triglycerides where LDL alone can understate risk.

A widely used rule of thumb sets each non-HDL cholesterol category 30 mg/dL (about 0.8 mmol/L) above the corresponding LDL category, reflecting an assumed VLDL cholesterol contribution of roughly 30 mg/dL at a typical triglyceride level near 150 mg/dL.

LDL category	Non-HDL cholesterol (mg/dL)	Non-HDL cholesterol (mmol/L)
Optimal (LDL below 100)	Below 130	Below 3.4
Near optimal (LDL 100-129)	130-159	3.4-4.1
Borderline high (LDL 130-159)	160-189	4.1-4.9
High (LDL 160-189)	190-219	4.9-5.7
Very high (LDL 190 and above)	220 and above	5.7 and above

Limitations

This calculation requires a fasting sample, traditionally 9 to 12 hours without food, because triglycerides rise sharply after eating and the equation was validated on fasting values; a typical meal can raise triglycerides by roughly 20 to 50 mg/dL within a few hours, and a fat-heavy meal can raise them considerably more, so a non-fasting triglyceride result can make the estimate unreliable even when the reported value is below 400 mg/dL.
The result is considered invalid above a triglyceride level of roughly 400 mg/dL (4.5 mmol/L); at that point the underlying assumption about VLDL composition breaks down and calculated LDL should not be used for clinical decisions.
The equation is inaccurate in rare disorders of lipoprotein metabolism, including type III hyperlipoproteinemia (dysbetalipoproteinemia) and conditions causing chylomicronemia, where VLDL composition differs from the population average the formula assumes.
Calculated LDL tends to be systematically less accurate, usually underestimated, at very low LDL levels, such as in people on intensive statin or other lipid-lowering therapy; a directly measured LDL is preferred for monitoring these patients.
This formula has not been validated for children, and its accuracy in pregnancy, when lipid levels change substantially, has not been established; it also does not measure LDL particle number or size, which some clinicians use as an additional risk marker.

Frequently asked questions

Why do I need to fast before a cholesterol test?

Fasting reduces the influence of a recent meal on triglycerides, which this calculation depends on. Some guidelines now allow non-fasting lipid panels for general screening, but a calculated LDL from a non-fasting sample is less reliable than one calculated from a fasting sample.

What happens if my triglycerides are above 400 mg/dL?

The calculation becomes unreliable, and many laboratories will not report a calculated LDL at all above this level. A clinician may order a directly measured LDL, use the Martin-Hopkins method if available, or rely on non-HDL cholesterol instead.

Is calculated LDL as accurate as a directly measured LDL?

For most people with normal triglycerides, the calculated and directly measured values are close. Accuracy declines as triglycerides rise or LDL falls very low, which is when a direct measurement or an alternative equation is more appropriate.

What is non-HDL cholesterol and how is it different?

Non-HDL cholesterol is total cholesterol minus HDL cholesterol. It captures LDL plus other atherogenic particles such as VLDL remnants, does not require a triglyceride-based estimate, and stays reliable even when triglycerides are high.

What is apolipoprotein B (apoB) and why is it sometimes ordered instead?

ApoB is a structural protein present on each LDL, VLDL, and remnant particle, so a direct apoB measurement counts the number of potentially artery-damaging particles rather than the amount of cholesterol they carry. Some clinicians order it in addition to, or instead of, calculated LDL when triglycerides are high or when LDL cholesterol and cardiovascular risk seem mismatched, since particle number and cholesterol content do not always move together.

What LDL level is considered a treatment target if I already have heart disease?

For people with established cardiovascular disease, a common secondary-prevention target is an LDL below 70 mg/dL (1.8 mmol/L), and some guidelines set a lower target of below 55 mg/dL (1.4 mmol/L) for those at very high risk. The exact target depends on individual risk factors and is set by a clinician, not by this calculator.

Do current guidelines still require fasting before a lipid panel?

Several major guidelines now accept a non-fasting lipid panel for general cardiovascular risk screening, since total cholesterol and HDL change little after eating. Fasting still matters specifically when triglycerides need to be accurate, including for this Friedewald-based LDL calculation, so a clinician may still request a fasting sample when calculated LDL, rather than a directly measured LDL or non-HDL cholesterol, is the value being used.