LDL Cholesterol Calculator (Friedewald Equation)
Use your lipid panel values to estimate LDL-C, non-HDL cholesterol, and total/HDL ratio.
Best used with fasting labs and triglycerides below the method limit.
What is the Friedewald formula?
The Friedewald formula is a widely used method to estimate low-density lipoprotein cholesterol (LDL-C), often called “bad cholesterol,” using standard lipid panel values. Instead of measuring LDL directly, the equation estimates it from total cholesterol, HDL cholesterol, and triglycerides.
It is popular because it is fast, inexpensive, and available in routine clinical testing workflows. For many people, this estimate is good enough for screening and monitoring cardiovascular risk over time.
The formula
When values are in mg/dL
LDL-C = Total Cholesterol − HDL-C − (Triglycerides / 5)
When values are in mmol/L
LDL-C = Total Cholesterol − HDL-C − (Triglycerides / 2.2)
The triglyceride divisor (5 in mg/dL or 2.2 in mmol/L) approximates very low-density lipoprotein cholesterol (VLDL-C). This is the key assumption behind the equation.
How to use this calculator
- Select your unit system (mg/dL or mmol/L).
- Enter total cholesterol, HDL cholesterol, and triglycerides from your lab report.
- Click Calculate to get estimated LDL-C, non-HDL-C, and total/HDL ratio.
- Review the interpretation text, then discuss results with your clinician.
What your result means
LDL-C is one piece of the cardiovascular risk puzzle. Blood pressure, diabetes status, smoking, family history, age, and inflammatory conditions all matter too. That said, LDL-C categories can still be useful for context:
- Optimal: lower LDL-C, especially in higher-risk patients, is generally better.
- Borderline to high: may prompt lifestyle changes and/or medication discussions.
- Very high: often requires further clinical evaluation.
When the Friedewald equation is less reliable
The formula has important limitations. It can become inaccurate when triglycerides are elevated, when samples are non-fasting, and in certain metabolic conditions.
- Triglycerides are ≥ 400 mg/dL (or ≥ 4.5 mmol/L).
- Very low LDL levels are being assessed (common in intensive lipid-lowering treatment).
- Unusual lipoprotein patterns are present (for example, dysbetalipoproteinemia).
- Recent food intake significantly alters triglyceride values.
Practical tips for better lipid tracking
1) Use the same lab when possible
Method differences between labs can create small shifts. Consistency improves trend tracking.
2) Keep conditions similar
Compare fasting-with-fasting or non-fasting-with-non-fasting whenever possible.
3) Focus on trends, not one number
Single values can fluctuate. Clinical decisions are usually based on repeated measurements and full risk context.
4) Pair numbers with action
Nutrition quality, regular physical activity, sleep, weight management, blood pressure control, and smoking cessation can all improve long-term cardiovascular outcomes.
Frequently asked questions
Is this calculator a diagnosis?
No. It is an educational estimate and cannot replace professional medical evaluation.
Can I use non-fasting values?
You can, but interpretation may be less accurate, especially if triglycerides are high. Follow your clinician’s testing instructions.
Why include non-HDL cholesterol and total/HDL ratio?
These metrics give additional context about atherogenic particles and lipid balance. Many clinicians consider non-HDL cholesterol particularly useful in risk assessment.
Bottom line
The Friedewald formula remains a practical and widely used tool for estimating LDL cholesterol. It is most useful when triglycerides are in range and testing conditions are stable. Use this calculator to understand your numbers, then review them with your healthcare professional for personalized guidance.