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LDL Cholesterol Calculator

Estimate your LDL with the Friedewald equation

Result

120 mg/dL

How it is calculated

Enter total cholesterol, HDL cholesterol and triglycerides, all in mg/dL from a lipid panel. The tool applies the Friedewald equation: LDL = Total − HDL − (Triglycerides / 5). The term Triglycerides / 5 is an estimate of VLDL cholesterol, which is removed along with HDL so that what remains is LDL. The result is rounded to a whole number of mg/dL.

The tool gives no result when triglycerides are 400 mg/dL or higher, when total cholesterol is zero or less, or when HDL or triglycerides are negative. It does not convert units: values in mmol/L would give a wrong answer because the divisor of 5 only fits mg/dL. The output is an estimate and not a replacement for a direct measurement or medical advice.

Worked example

Total cholesterol 200 mg/dL, HDL 50 mg/dL, triglycerides 150 mg/dL. First estimate VLDL: 150 / 5 = 30. Then subtract HDL and VLDL from the total: 200 − 50 − 30 = 120. The result is 120 mg/dL of LDL.

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Common mistakes

  • Entering mmol/L values. A panel reporting total cholesterol 5.2 will give a nonsense result here; the tool needs mg/dL, which is roughly 38.67 times the mmol/L figure for cholesterol.
  • Using the result with triglycerides at 400 mg/dL or above. The tool deliberately returns nothing there, because the VLDL estimate stops being reliable.
  • Swapping HDL and LDL or typing LDL in the HDL box, which makes the calculation circular and the answer meaningless.
  • Mixing a fasting value with a non-fasting one. Triglycerides drawn after a meal are higher, which pushes the estimated LDL down.
  • Ignoring a negative or tiny answer. If the inputs are inconsistent (for example HDL plus triglycerides/5 larger than the total), the tool can show a negative number, which signals a typing error.

Sources

About this calculator

This calculator uses the Friedewald equation, the formula labs have used for decades to estimate "bad" cholesterol without directly measuring it: LDL = Total Cholesterol − HDL − (Triglycerides ÷ 5), all in mg/dL (the divisor is 2.2 when working in mmol/L). It works because VLDL cholesterol — the third major lipoprotein — is roughly one-fifth of the triglyceride level in a fasting sample, so subtracting that estimate along with HDL isolates LDL.

It's the calculation behind most standard lipid panel reports and is what your doctor is reading when discussing "LDL" from routine bloodwork. The formula becomes unreliable and is not reported when triglycerides exceed 400 mg/dL, since the VLDL approximation breaks down — in that case labs switch to direct LDL measurement or the newer Martin-Hopkins method instead.

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Comments (1)

  • Editorial team

    Because the formula subtracts one fifth of triglycerides, two panels with the same total and HDL give different LDL values only because of triglycerides. A total of 200, HDL of 50 and triglycerides of 150 gives 120 mg/dL, while triglycerides of 250 give 100. That gap comes from the estimate, not necessarily from your body. Talk to your doctor about what any number means. Does your lab print a measured LDL that differs from this estimate?

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