Printed on 3/17/2026
For informational purposes only. This is not medical advice.
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
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).
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).
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.
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 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.
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.
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.
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).
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.
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.
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.
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.
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 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 (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.
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).
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).
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%.
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.
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.
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.
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.
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.
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