LDL Calculator
A lipid panel with total cholesterol 210 mg/dL, HDL 50 mg/dL, and triglycerides 150 mg/dL gives an estimated LDL of 130 mg/dL. This LDL calculator uses the Friedewald equation to estimate LDL cholesterol from total cholesterol, HDL cholesterol, and triglycerides. Enter all three values in mg/dL, and use the result only when the common limits of the equation fit your lab result.
Quick answer
The Friedewald equation estimates LDL-C as total cholesterol minus HDL-C minus triglycerides divided by 5.
What this tells you
- •The Friedewald equation estimates LDL-C as total cholesterol minus HDL-C minus triglycerides divided by 5.
- •This tool expects all three inputs in mg/dL.
- •The equation is commonly used only when triglycerides are below 400 mg/dL.
- •The result is an estimate, not a direct LDL measurement.
How to Use
- 1Enter total cholesterol in mg/dL from your lipid panel.
- 2Enter HDL cholesterol in mg/dL.
- 3Enter triglycerides in mg/dL.
- 4Calculate to see the estimated LDL value, the estimated VLDL portion, and non-HDL cholesterol.
- 5If triglycerides are 400 mg/dL or higher, or the result does not fit the rest of the panel, use your lab report or clinician guidance instead of this estimate.
How It Works
Formula
Friedewald equation: LDL-C = total cholesterol - HDL-C - (triglycerides / 5)
All inputs must be in mg/dL
Example: 210 - 50 - (150 / 5) = 130 mg/dLThe equation first estimates the cholesterol carried by very-low-density lipoproteins by dividing triglycerides by 5. It then subtracts HDL cholesterol and that estimated VLDL portion from total cholesterol to estimate LDL cholesterol. This shortcut is widely taught, but it is still an estimate, so labs may use a direct LDL test or a different equation when the panel falls outside the common use range.
Calculation note: values are processed in the order shown above, using the current input units.
Worked Examples
Common adult lipid-panel example
Triglycerides divided by 5 gives an estimated VLDL portion of 30 mg/dL. Then 210 - 50 - 30 = 130.
Lower triglyceride example
The estimated VLDL portion is 19 mg/dL. Subtract 52 and 19 from 187 to get 116 mg/dL.
Common Friedewald Equation Checks
Use these quick checks before relying on a Friedewald LDL estimate from a standard lipid panel.
| Check | Why it matters | How this tool handles it |
|---|---|---|
| All values in mg/dL | The triglycerides ÷ 5 step in this form assumes mg/dL units. | Enter total cholesterol, HDL, and triglycerides in mg/dL only. |
| Triglycerides below 400 mg/dL | The VLDL estimate becomes less reliable when triglycerides are high. | The tool rejects 400 mg/dL and higher. |
| HDL not above total cholesterol | HDL is one part of total cholesterol, so HDL cannot be larger than the total. | The tool rejects impossible panels. |
| Estimated LDL not negative | A negative LDL result usually means the panel does not fit the equation well or the inputs are wrong. | The tool rejects negative LDL estimates. |
A valid Friedewald estimate can still differ from a direct LDL measurement or a lab that uses another equation.
Common mistakes
- Mixing mg/dL and mmol/L values in one calculation.
- Using the Friedewald equation when triglycerides are 400 mg/dL or higher.
- Treating an estimated LDL number as a diagnosis or a treatment instruction by itself.
Limitations
This calculator uses the Friedewald equation in mg/dL only. It does not convert units, and it does not estimate LDL when triglycerides are 400 mg/dL or higher, when HDL is greater than total cholesterol, or when the math produces a negative LDL result. Even inside the common use range, the estimate can differ from a direct LDL measurement because of fasting status, very low LDL values, medication effects, lab methods, and other clinical factors.