LDL Calculator

Estimate your LDL cholesterol using the Friedewald formula from total cholesterol, HDL, and triglycerides.

What Is the LDL Calculator?

This tool estimates your LDL (low-density lipoprotein) cholesterol level using the Friedewald formula. LDL cholesterol is often referred to as "bad" cholesterol because elevated levels can contribute to plaque buildup in arteries. The calculator requires three values from a standard lipid panel: total cholesterol, HDL cholesterol, and triglycerides.

The result is an estimate, not a direct measurement. It provides a useful reference for understanding cardiovascular risk, but should not replace professional medical interpretation.

How the Friedewald Formula Works

The calculator applies the standard Friedewald equation:

LDL = Total Cholesterol − HDL − (Triglycerides / 5)

The formula assumes that VLDL (very low-density lipoprotein) can be approximated as triglycerides divided by 5. This works reliably when triglyceride levels are below 400 mg/dL. Above that threshold, the estimate becomes less accurate because the VLDL-to-triglyceride ratio shifts.

All values must be entered in mg/dL. If your lab results use mmol/L, convert them before using this calculator.

How to Use the Calculator

Enter your total cholesterol value in mg/dL.
Enter your HDL cholesterol value in mg/dL.
Enter your triglyceride value in mg/dL.
Click calculate to see your estimated LDL cholesterol.

No additional inputs are needed. The calculator handles the math instantly.

Understanding Your Results

The output is a single number representing estimated LDL cholesterol in mg/dL. General reference ranges for LDL are:

Optimal: Below 100 mg/dL
Near optimal: 100–129 mg/dL
Borderline high: 130–159 mg/dL
High: 160–189 mg/dL
Very high: 190 mg/dL and above

These ranges are guidelines. Your target LDL may differ based on existing health conditions, risk factors, and treatment goals. Always discuss results with a healthcare provider.

When the Estimate May Be Less Accurate

The Friedewald formula has known limitations:

Triglycerides above 400 mg/dL: The VLDL approximation breaks down, making the LDL estimate unreliable.
Very low LDL levels: Accuracy decreases when LDL is below 70 mg/dL.
Non-fasting samples: Triglyceride levels rise after eating, which can skew the calculation. Fasting for 9–12 hours before blood draw is recommended.
Certain medical conditions: Diabetes, kidney disease, and some metabolic disorders can alter the relationship between triglycerides and VLDL.

If any of these apply, direct LDL measurement (via ultracentrifugation or other methods) may be more appropriate.

Practical Use Cases

Monitoring between lab visits: Track estimated LDL changes when full lipid panel results are available.
Understanding lab reports: Some labs report calculated LDL directly. This tool helps you verify that calculation.
Assessing treatment progress: See how lifestyle changes or medications affect estimated LDL over time.

FAQ

Why does the calculator need triglycerides?

Triglycerides are used to estimate VLDL cholesterol, which is then subtracted from total cholesterol along with HDL. Without triglycerides, the formula cannot separate LDL from other cholesterol components.

Can I use this if my triglycerides are over 400 mg/dL?

The Friedewald formula is not reliable above 400 mg/dL. The calculator will still produce a number, but it should not be considered accurate. Direct LDL measurement is recommended in this case.

Is calculated LDL the same as measured LDL?

No. Calculated LDL is an estimate based on a mathematical formula. Direct LDL measurement uses laboratory techniques to isolate and measure LDL directly. For most people with normal triglyceride levels, the estimate is close enough for clinical use.

What if my result seems too low or too high?

Double-check your input values. Common errors include entering HDL in the wrong unit or mixing up total cholesterol and HDL values. If the inputs are correct and the result seems unusual, consult your doctor for a direct measurement.

Does this calculator work for children?

The Friedewald formula is commonly used for adults. Pediatric lipid interpretation uses different reference ranges and may require direct measurement depending on the clinical context.