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.
What the Friedewald estimate can and cannot show
Use total cholesterol, HDL cholesterol, and triglycerides from the same lipid panel. In the mg/dL form, triglycerides divided by 5 estimates cholesterol carried in very-low-density lipoproteins. Subtracting that value and HDL from total cholesterol leaves the LDL estimate. The VLDL result shown here is part of the equation, not a direct VLDL assay.
The factor of 5 is unit-specific. A panel in mmol/L needs a different form of the equation and should not be entered here. Converting each lipid also requires the correct analyte conversion because cholesterol and triglycerides do not share the same mass-to-molar factor. Use a validated lipid converter or the laboratory's mg/dL values rather than changing the unit label mentally.
The implementation accepts triglycerides from zero up to, but not including, 400 mg/dL. It also requires positive total cholesterol and HDL, rejects HDL above total cholesterol, and rejects a negative calculated LDL. Passing these checks only means the arithmetic fits the programmed domain. It does not guarantee that Friedewald is the best estimate for that sample.
Accuracy can be weaker when triglycerides are elevated, LDL is low, or the relationship between triglycerides and VLDL cholesterol differs from the equation's assumption. Fasting status, diabetes, acute illness, alcohol use, pregnancy, kidney or liver disease, medicines, and other clinical circumstances can influence the lipid panel or method choice. A laboratory may use another equation or direct measurement.
Non-HDL cholesterol is total cholesterol minus HDL. It includes cholesterol in LDL and other atherogenic particles. The calculator reports it because the subtraction is available from the same inputs, but it does not set a personal target. Treatment thresholds and goals depend on overall cardiovascular risk, medical history, age, blood pressure, smoking, diabetes, kidney disease, medications, and current guidance.
Analytical and biological variation mean two valid tests can differ. Sample handling, assay method, recent illness, fasting conditions, and ordinary within-person variation may contribute. Compare trends using the actual laboratory reports and note when methods or conditions changed. Do not overinterpret a one-decimal difference from a rounded calculator output.
The calculator rounds estimated LDL, estimated VLDL, and non-HDL to one decimal place. A lab can report another precision or use unrounded internal values. If a clinician or report provides LDL directly, use that reported value and method for clinical discussion instead of substituting this independent estimate.
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.
- Combining total cholesterol, HDL, and triglycerides from different blood draws.
- Entering a directly reported LDL value into one of the component fields.
- Assuming every laboratory uses Friedewald rather than another validated equation or direct method.
Limitations
This calculator uses only the Friedewald equation in mg/dL. It requires one internally consistent lipid panel, triglycerides below 400 mg/dL, HDL no greater than total cholesterol, and a nonnegative result. It does not convert mmol/L, validate an assay, measure LDL or VLDL directly, or choose among newer equations. Accuracy may be limited with elevated triglycerides, low LDL, nonfasting samples, diabetes, pregnancy, acute illness, kidney or liver disease, altered lipoprotein patterns, or medication effects. It does not account for age, personal cardiovascular risk, treatment targets, symptoms, family history, or laboratory-specific methods and flags.
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