🧪 LDL Cholesterol Calculator
Estimate LDL-C when direct measurement is unavailable using the Friedewald formula and interpret cardiovascular risk.
Friedewald: LDL = Total − HDL − (Triglycerides ÷ 5)
How to Use This Calculator
Collect fasting lipid results
Obtain total cholesterol, HDL-C, and triglycerides from a fasting lipid panel. Non-fasting values may overestimate LDL if triglycerides rise significantly.
Enter data in consistent units
Select mg/dL or mmol/L, input the lab values, and click “Calculate LDL-C.” The tool handles unit conversion automatically.
Review LDL, non-HDL, and ratio
Use the outputs to guide decisions about statin therapy, lifestyle modification, and follow-up testing per ACC/AHA or ESC guidelines.
Formula
The Friedewald equation (1972) estimates LDL-C when triglycerides are not markedly elevated:
- LDL (mg/dL) = Total Cholesterol − HDL − (Triglycerides ÷ 5)
- LDL (mmol/L) = Total (mmol/L) − HDL (mmol/L) − (Triglycerides ÷ 2.2)
- Non-HDL = Total − HDL
- Total/HDL ratio = Total ÷ HDL
Alternative equations (Martin-Hopkins, Sampson/NIH) improve accuracy when triglycerides are elevated or LDL is low. Order direct LDL when triglycerides ≥ 400 mg/dL or patient has dysbetalipoproteinemia.
Full Description
LDL cholesterol is the primary target for atherosclerotic cardiovascular disease prevention. Most clinical guidelines stratify statin therapy based on LDL thresholds (e.g., ≥ 190 mg/dL triggers high-intensity statins, ≥ 70 mg/dL triggers therapy post-MI).
The Friedewald formula provides a quick estimate for routine practice. However, it underestimates LDL when triglycerides are high or LDL is low (as in high-intensity statin therapy). In such cases, use direct LDL assays or more advanced calculations.
Combine LDL with non-HDL cholesterol, apolipoprotein B, coronary calcium scoring, and lifestyle risk factors to personalise prevention strategies and achieve optimal outcomes.
Frequently Asked Questions
Do I need fasting labs for this formula?
Fasting is preferred because triglycerides can rise after meals, increasing the estimation error. For non-fasting panels, use caution or consider direct LDL measurement.
What if my LDL result is negative?
Negative values indicate very low LDL or data entry errors. Recheck inputs and confirm with direct LDL or an alternative equation if needed.
How often should I recheck LDL?
After starting or changing therapy, remeasure in 4-12 weeks. Once stable, test every 3-12 months depending on risk profile and guideline recommendations.
Is non-HDL better than LDL?
Non-HDL captures all atherogenic particles and is especially valuable when triglycerides are high. Many experts consider it a secondary goal after LDL.
Can I use this for children?
Paediatric lipid management follows specific thresholds. Use the formula cautiously and consult paediatric lipid specialists for interpretation.