How is LDL calculated?

Friedewald equation: LDL = Total Cholesterol - HDL - (Triglycerides/5), with all values in mg/dL. It estimates VLDL cholesterol as triglycerides divided by 5 (the ratio of triglyceride to cholesterol in VLDL particles), then subtracts VLDL and HDL from total cholesterol to derive LDL. This formula was developed in 1972 and remains widely used.

When is Friedewald LDL less reliable?

Unreliable when: (1) Triglycerides ≥400 mg/dL (VLDL estimation breaks down), (2) Very low LDL <70 mg/dL (underestimates true LDL by 5-10 mg/dL), (3) Non-fasting samples with very high triglycerides, (4) Type 3 dyslipidemia (abnormal VLDL remnants). In these cases, order direct LDL measurement or use Martin-Hopkins equation (more accurate).

What is non-HDL cholesterol?

Non-HDL cholesterol = Total Cholesterol - HDL. It captures all atherogenic (plaque-forming) lipoproteins: LDL, VLDL, IDL, remnants, and Lp(a). Non-HDL is a secondary treatment target. Target: <30 mg/dL above your LDL goal. Example: if LDL goal is <100, non-HDL goal is <130. Non-HDL is more predictive than LDL alone, especially when triglycerides are elevated.

Should I rely on one LDL number alone?

No. LDL should be interpreted with: (1) full lipid panel (HDL, triglycerides, non-HDL), (2) overall cardiovascular risk (ASCVD Risk Score, diabetes, hypertension, smoking), (3) family history, (4) comorbidities (CKD, inflammatory diseases), (5) advanced lipid markers if available (apoB, Lp(a), LDL particle number). Use ASCVD Risk Calculator to guide treatment intensity.

What are optimal LDL levels?

Depends on cardiovascular risk: Very high risk (prior MI/stroke, recent ACS, diabetes + target organ damage): <55 mg/dL. High risk (secondary prevention, diabetes, ASCVD risk ≥20%): <70 mg/dL. Moderate risk (ASCVD risk 7.5-20%): <100 mg/dL. Lower risk (ASCVD risk <7.5%): <130 mg/dL. General population without risk factors: <100 mg/dL is considered optimal.

What is the difference between direct LDL and calculated LDL?

Calculated LDL (Friedewald): Derived from total cholesterol, HDL, and triglycerides using a formula. Free (no extra cost), accurate for most patients, but inaccurate when triglycerides ≥400 or LDL <70. Direct LDL: Measured directly by lab assay (ultracentrifugation or homogeneous assay). More accurate in edge cases, costs extra (~$10-30). Order direct LDL when Friedewald is unreliable.

What is the Martin-Hopkins equation?

An improved LDL calculation formula published in 2013 that adjusts the triglyceride/VLDL ratio based on measured triglyceride and non-HDL levels, rather than using a fixed ratio of 5. It's more accurate than Friedewald when triglycerides are high (200-800 mg/dL) or LDL is low (<70 mg/dL). Some labs now report Martin-Hopkins calculated LDL instead of Friedewald.

What is the total cholesterol/HDL ratio?

Total cholesterol divided by HDL cholesterol. Optimal: 5.0. This ratio predicts cardiovascular risk better than total cholesterol or LDL alone. Example: Total 200, HDL 60 → ratio = 3.3 (good). Total 240, HDL 40 → ratio = 6.0 (high risk). Raise HDL through exercise, weight loss, smoking cessation, and moderate alcohol consumption.

What is the triglyceride/HDL ratio?

Triglycerides divided by HDL. Optimal: 3.0. Very high: >6.0. High triglyceride/HDL ratio indicates insulin resistance and small dense LDL particles (more atherogenic). Example: Triglycerides 150, HDL 50 → ratio = 3.0 (borderline). Triglycerides 200, HDL 35 → ratio = 5.7 (high — indicates metabolic syndrome, insulin resistance). Improve with weight loss, low-carb diet, exercise.

How much do statins lower LDL?

High-intensity statins (atorvastatin 40-80 mg, rosuvastatin 20-40 mg): Lower LDL by ≥50%. Moderate-intensity statins (atorvastatin 10-20 mg, rosuvastatin 5-10 mg, simvastatin 20-40 mg, pravastatin 40-80 mg): Lower LDL by 30-49%. Low-intensity statins (simvastatin 10 mg, pravastatin 10-20 mg, lovastatin 20 mg): Lower LDL by <30%. Choose intensity based on baseline LDL and target LDL.

What if I can't reach my LDL goal on a statin?

Options: (1) Increase statin dose (if tolerating current dose), (2) Switch to more potent statin (e.g., pravastatin → atorvastatin → rosuvastatin), (3) Add ezetimibe (Zetia) — lowers LDL additional 15-20%, (4) Add PCSK9 inhibitor (evolocumab, alirocumab) — lowers LDL additional 50-60% (expensive, reserved for high-risk patients), (5) Add bempedoic acid — lowers LDL 15-25% (alternative to ezetimibe). Use combination therapy to reach aggressive goals (<55 mg/dL).

What is familial hypercholesterolemia?

Genetic disorder causing very high LDL cholesterol (often >190 mg/dL) from birth due to mutations in LDL receptor, apoB, or PCSK9 genes. Affects 1 in 250 people. Leads to premature cardiovascular disease (heart attacks in 40s-50s). Diagnosis: LDL >190 mg/dL + family history of high cholesterol or early heart disease. Treatment: High-intensity statin + ezetimibe + PCSK9 inhibitor often needed. Screen family members.

Does diet really affect cholesterol?

Yes, but effect varies by person. Dietary cholesterol (eggs, shrimp) has minimal effect for most people (liver compensates by making less cholesterol). Saturated fat (red meat, butter, coconut oil) raises LDL by 5-15% on average. Trans fats (hydrogenated oils — now mostly banned) raise LDL and lower HDL significantly. Portfolio diet (plant sterols, soluble fiber, soy protein, nuts) can lower LDL by 10-15%. However, genetics often dominate — many people need statins regardless of diet.

Should I be concerned about high HDL?

Generally no. Very high HDL (>80 mg/dL) is usually protective, not harmful. However, extremely high HDL (>100 mg/dL) may be dysfunctional in rare cases and does not provide additional benefit beyond HDL 60-80 mg/dL. Focus on raising low HDL (<40 mg/dL men, <50 mg/dL women) through lifestyle changes. Remember: HDL is less important than LDL — you can't 'outrun' high LDL with high HDL.

How often should I check my cholesterol?

Adults 20-39 without risk factors: Every 5 years. Adults 40-75 for ASCVD risk assessment: Every 4-6 years. High risk or on statin therapy: Every 3-12 months (check 4-12 weeks after starting/changing statin to assess response, then annually if stable). After reaching goal: Annually. More frequent if treatment intensification needed or adherence concerns.

Online Medical Tools — LDL Calculator

Printed on 8/14/2026

For informational purposes only. This is not medical advice.

Cardiology

LDL Calculator

This LDL calculator estimates LDL-C using the Friedewald equation (LDL = Total Cholesterol - HDL - Triglycerides/5, mg/dL), and also reports non-HDL cholesterol and the total-to-HDL ratio for additional cardiovascular risk context. It is commonly used when direct LDL testing is not available.

Formula: Friedewald: LDL = Total Cholesterol - HDL - (Triglycerides/5), mg/dL

Total Cholesterol

mg/dL

HDL Cholesterol

mg/dL

Triglycerides

mg/dL

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Keep a history of calculations, favorite tools, and access your dashboard anytime.

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How It Works

Enter your lipid panel values

Input total cholesterol, HDL cholesterol ('good' cholesterol), and triglycerides from your lab results. These are typically measured together in a standard lipid panel, ideally after 9-12 hours fasting (though non-fasting panels are increasingly accepted).

Calculate LDL using Friedewald equation

The calculator applies the Friedewald formula: LDL = Total Cholesterol - HDL - (Triglycerides / 5). This estimates VLDL cholesterol as triglycerides divided by 5, then subtracts VLDL and HDL from total cholesterol to derive LDL ('bad' cholesterol).

Review LDL, non-HDL, and cholesterol ratios

LDL is your primary treatment target. Non-HDL cholesterol (total - HDL) captures all atherogenic particles. Total cholesterol/HDL ratio provides additional risk context — optimal ratio is <3.5. These metrics together guide statin therapy decisions and cardiovascular risk assessment.

Who Uses the LDL Calculator

Home Lipid Panel Review

Individuals monitoring cholesterol

Calculate LDL from your lab results when only total cholesterol, HDL, and triglycerides are reported. Many lab reports don't calculate LDL if triglycerides are high (>400 mg/dL) — this calculator shows when Friedewald is unreliable.

Primary Care Lipid Management

Primary care physicians, NPs, PAs

Calculate LDL to guide statin therapy per ACC/AHA guidelines. LDL targets: <70 mg/dL (very high risk/secondary prevention), <100 mg/dL (high risk/diabetes), <130 mg/dL (moderate risk). Use with ASCVD Risk Calculator to determine treatment intensity.

Medication Response Tracking

Cardiologists, lipidologists

Monitor LDL reduction on statin therapy. High-intensity statins lower LDL by ≥50%; moderate-intensity by 30-49%. Recheck lipids 4-12 weeks after starting/adjusting statin. If LDL goal not achieved, consider intensifying therapy or adding ezetimibe/PCSK9 inhibitor.

Secondary Prevention Target Setting

Post-MI, post-stroke, CAD patients

For secondary prevention (existing ASCVD), LDL target is <70 mg/dL, with <55 mg/dL increasingly recommended for very high-risk patients (recent ACS, recurrent events, diabetes + target organ damage). Calculate LDL to track progress toward aggressive goals.

Non-Fasting Lipid Panel Interpretation

Clinicians, lab interpreters

Non-fasting lipids are now acceptable for most patients. Total cholesterol and HDL change minimally after eating; triglycerides rise modestly (usually <30 mg/dL). Calculate LDL from non-fasting panels unless triglycerides are very elevated (>400 mg/dL).

When Friedewald Fails (High Triglycerides)

Lipid specialists, endocrinologists

Friedewald equation becomes inaccurate when triglycerides ≥400 mg/dL (underestimates VLDL). This calculator identifies when direct LDL measurement is needed. Alternative: Martin-Hopkins equation (more accurate at high triglycerides and low LDL) or direct LDL assay.

Pro Tips

Non-HDL is increasingly important

Non-HDL cholesterol (total - HDL) includes all atherogenic particles (LDL, VLDL, IDL, Lp(a), remnants). It's more predictive than LDL alone and works even when triglycerides are high (>400 mg/dL). 2018 ACC/AHA guidelines recommend non-HDL as secondary target: aim for non-HDL <30 mg/dL above your LDL goal.

Friedewald underestimates LDL at low levels

When LDL is <70 mg/dL (common on high-intensity statins), Friedewald may underestimate true LDL by 5-10 mg/dL. Martin-Hopkins equation is more accurate here. For very aggressive LDL targets (<55 mg/dL), consider direct LDL measurement to avoid underestimation.

Total cholesterol/HDL ratio is a powerful predictor

Optimal ratio: <3.5. Ideal: <3.0. High risk: >5.0. This ratio often outperforms LDL alone for predicting cardiovascular events. Example: 200/60 = 3.3 (good), 240/40 = 6.0 (high risk). Raise HDL through exercise, weight loss, moderate alcohol, and smoking cessation.

LDL targets depend on your cardiovascular risk

Very high risk (prior MI/stroke, diabetes + target organ damage): <55 mg/dL. High risk (secondary prevention, diabetes, 10-year ASCVD risk ≥20%): <70 mg/dL. Moderate risk (10-year risk 7.5-20%): <100 mg/dL. Low risk (<7.5%): <130 mg/dL. Personalize targets using shared decision-making.

Triglycerides affect Friedewald accuracy

Triglycerides 150-199 mg/dL: Friedewald reasonably accurate. 200-399 mg/dL: Friedewald less accurate but usable. ≥400 mg/dL: Friedewald invalid — order direct LDL. Very low triglycerides (<100 mg/dL): Friedewald may overestimate VLDL and underestimate LDL.

Fasting vs non-fasting lipids

Fasting (9-12 hours): Triglycerides lowest, LDL most accurate. Non-fasting: Triglycerides 20-30 mg/dL higher on average (but individual variation). Total cholesterol and HDL barely change. Non-fasting panels are acceptable for most patients; fasting preferred if triglycerides were previously high or for precision.

Direct LDL vs calculated LDL

Calculated LDL (Friedewald): Free, derived from lipid panel, accurate for most patients. Direct LDL: Separate lab assay, costs extra, more accurate when triglycerides are high (>400) or LDL is very low (<70). Order direct LDL if Friedewald is unreliable or precision is critical (e.g., familial hypercholesterolemia diagnosis).

Apolipoprotein B (apoB) is the most accurate marker

ApoB measures the number of atherogenic particles (each LDL, VLDL, IDL, Lp(a) particle has one apoB). It's more accurate than LDL for predicting cardiovascular risk, especially when triglycerides are high or HDL is low. Target apoB: <80 mg/dL (high risk), <100 mg/dL (moderate risk). Consider ordering for discordant risk (high triglycerides + low LDL).

Lipoprotein(a) is an independent risk factor

Lp(a) is a genetic LDL-like particle not captured by standard LDL measurement. Elevated Lp(a) (>50 mg/dL or >125 nmol/L) increases cardiovascular risk by 2-4 fold. Screen once in lifetime, especially if premature ASCVD, family history, or calcific aortic stenosis. No proven therapy yet, but PCSK9 inhibitors lower Lp(a) by ~25%.

Reassess lipids 4-12 weeks after starting/changing statins

Statins reach steady-state effect in 4-6 weeks. Recheck lipids at 4-12 weeks to assess response. If LDL goal not achieved, increase statin dose, switch to more potent statin, or add ezetimibe (lowers LDL additional 15-20%). Don't wait months to titrate — early optimization improves outcomes.

Common Questions About Your Results

Possible causes: (1) Non-adherence (most common — statins must be taken daily), (2) Insufficient dose (low-intensity statin may not lower LDL enough), (3) Statin resistance (rare genetic mutations), (4) Medication interaction (some drugs reduce statin absorption), (5) Familial hypercholesterolemia (genetic condition requiring aggressive therapy). Discuss with your doctor — may need dose increase, switch to more potent statin, or add ezetimibe/PCSK9 inhibitor.

No longer required for most people. Non-fasting lipids are acceptable per 2016 European and 2018 ACC/AHA guidelines. Total cholesterol and HDL barely change after eating; triglycerides rise modestly (usually <30 mg/dL). Fasting preferred if: (1) prior triglycerides ≥400 mg/dL, (2) non-fasting triglycerides >400 mg/dL (retest fasting), (3) familial lipid disorder suspected, (4) monitoring triglyceride-lowering therapy. Otherwise, non-fasting is convenient and accurate.

Evidence-Based Methodology

The Friedewald equation (Clin Chem 1972) has been the standard LDL calculation method for 50+ years. Martin-Hopkins equation (JAMA 2013) improves accuracy at high triglycerides and low LDL. 2018 ACC/AHA Blood Cholesterol Guidelines recommend non-HDL as secondary target (30 mg/dL above LDL goal). LDL targets are from 2018 ACC/AHA Cholesterol Guidelines and 2019 ESC/EAS Dyslipidaemia Guidelines.

Clinical Content Trust

Last reviewed:: April 21, 2026
Guideline version:: General evidence framework v2026.04
Source set version:: Primary-source set v1

How to Interpret Your Result

Your calculated LDL provides an estimate of LDL-C burden from your lipid panel. Lower LDL is generally associated with lower atherosclerotic cardiovascular risk, especially in people with multiple risk factors or established vascular disease.

Non-HDL and total/HDL ratio add context. Non-HDL includes all apoB-containing atherogenic lipoproteins, while the ratio gives a quick risk signal that should be interpreted alongside absolute lipid values.

When to Use This Tool

Use this tool when reviewing fasting or non-fasting lipid panel results and you want a quick LDL estimate and supporting lipid indices. It is useful in preventive care follow-up and medication/lifestyle response tracking.

For treatment planning, pair this with ASCVD risk tools to align lipid results with overall risk and guideline-based intensity of intervention.

Limitations

Friedewald LDL is generally not valid when triglycerides are 400 mg/dL or above and can be less accurate at very low LDL concentrations. In these settings, direct LDL testing or alternative equations may be preferred.

This calculator does not replace individualized risk assessment. Family history, diabetes, chronic kidney disease, inflammatory disorders, lipoprotein(a), and existing ASCVD can materially change LDL targets and treatment decisions.

Disclaimer: This tool is for educational and informational purposes only. It is not a substitute for professional medical advice, diagnosis, or treatment. Always consult a qualified healthcare provider with questions about your health.

Changelog

April 21, 2026 · trust-baseline
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Related Tools

Cardiology

Online Medical Tools — LDL Calculator

LDL Calculator

How It Works

Enter your lipid panel values

Calculate LDL using Friedewald equation

Review LDL, non-HDL, and cholesterol ratios

Who Uses the LDL Calculator

Home Lipid Panel Review

Primary Care Lipid Management

Medication Response Tracking

Secondary Prevention Target Setting

Non-Fasting Lipid Panel Interpretation

When Friedewald Fails (High Triglycerides)

Pro Tips

Non-HDL is increasingly important

Friedewald underestimates LDL at low levels

Total cholesterol/HDL ratio is a powerful predictor

LDL targets depend on your cardiovascular risk

Triglycerides affect Friedewald accuracy

Fasting vs non-fasting lipids

Direct LDL vs calculated LDL

Apolipoprotein B (apoB) is the most accurate marker

Lipoprotein(a) is an independent risk factor

Reassess lipids 4-12 weeks after starting/changing statins

Common Questions About Your Results

Evidence-Based Methodology

Clinical Content Trust

How to Interpret Your Result

When to Use This Tool

Limitations

Changelog

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ASCVD Risk Calculator

Framingham Risk

Heart Age Calculator

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Further Reading

Cardiovascular Risk Assessment: ASCVD, Framingham, and Statin Therapy Explained

Frequently Asked Questions