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LDL Calculator: Friedewald and NIH Equations
Calculated LDL-C is total cholesterol minus HDL minus an estimate of VLDL. Friedewald uses triglycerides ÷ 5 (mg/dL) and was built for triglycerides under 400 mg/dL; the NIH (Sampson 2020) equation extends to 800 mg/dL. With total 200, HDL 50 and triglycerides 150 mg/dL, Friedewald gives 120 and the NIH equation gives 123 mg/dL.
Prepared by Prospyr · Reviewed October 3, 2026 · Free, no sign-up, runs in your browser
Both equations were built for standard lipid panel values.
Calculated LDL-C (NIH / Sampson equation)
123mg/dL
Friedewald: 120 mg/dL
Non-HDL-C (TC − HDL)
150 mg/dL
VLDL-C (TG ÷ 5, Friedewald)
30 mg/dL
Decision support only; it does not replace clinical judgment. Calculated LDL-C is an estimate; a direct measurement can differ.
LDL calculation formulas: Friedewald and NIH
- Friedewald (1972): LDL-C = TC − HDL-C − TG ÷ 5 (mg/dL) or TG ÷ 2.2 (mmol/L)
- NIH / Sampson (2020), mg/dL: LDL-C = TC ÷ 0.948 − HDL-C ÷ 0.971 − (TG ÷ 8.56 + TG × non-HDL-C ÷ 2140 − TG² ÷ 16,100) − 9.44, where non-HDL-C = TC − HDL-C
The NIH equation is only defined in mg/dL, so mmol/L entries are converted (cholesterol ÷ 38.67, triglycerides ÷ 88.57) before it runs and the result is converted back.
Worked examples
| TC / HDL / TG (mg/dL) | Friedewald | NIH |
|---|---|---|
| 200 / 50 / 150 | 200 − 50 − 30 = 120 | 123 |
| 250 / 35 / 500 | 115 (TG 400 or more, unreliable) | 125 |
In the second row Friedewald subtracts a VLDL estimate of 100. Because that fixed factor of 5 breaks down at high triglycerides, the tool flags the result.
Calculated LDL when triglycerides are high
Friedewald assumes VLDL cholesterol is one fifth of triglycerides. Martin and colleagues (JAMA 2013) showed that ratio varies with triglyceride and non-HDL levels, and proposed an adjustable factor from a 180-cell table. Sampson and colleagues built a regression equation from 8,656 NIH patients; against the β-quantification reference it had an RMSE of 15.2 mg/dL versus 32 for Friedewald and 25.7 for the Martin equation in their data.
Any calculated LDL is an estimate. For other lab math, see the cholesterol ratio calculator.
In a practice workflow
If your team reviews lipid panels for weight or hormone programs, keep the panel with the visit in charting. See med spa software for the rest of the workflow.
Frequently asked questions
What is the Friedewald formula for LDL?
LDL-C = total cholesterol − HDL-C − triglycerides ÷ 5 in mg/dL, or triglycerides ÷ 2.2 in mmol/L. Friedewald, Levy and Fredrickson published it in Clinical Chemistry in 1972.
When is the Friedewald equation not reliable?
When triglycerides are 400 mg/dL (4.5 mmol/L) or higher. Sampson and colleagues note that calculating LDL-C is less accurate in patients with a low LDL-C or with triglycerides of 400 mg/dL or more. The calculator flags those results.
What is the NIH (Sampson) LDL equation?
It is LDL-C = TC ÷ 0.948 − HDL ÷ 0.971 − (TG ÷ 8.56 + TG × non-HDL ÷ 2140 − TG² ÷ 16100) − 9.44, in mg/dL. Sampson and colleagues (JAMA Cardiology, 2020) report it is as accurate up to triglycerides of 800 mg/dL as Friedewald is below 400.
Is there a Martin-Hopkins LDL calculator here?
No. The Martin-Hopkins method replaces the fixed factor of 5 with a value looked up in a 180-cell table of triglyceride and non-HDL strata, and this page does not include that table. It compares Friedewald with the NIH equation instead.
What if my triglycerides are above 800 mg/dL?
The calculator will not show an NIH value, because the equation was not validated there. A directly measured LDL-C is the way to get a number in that range.
Does this calculator say what LDL level a patient should aim for?
No. It calculates the published equations only. Targets and treatment decisions come from the treating provider and current guidelines.
Sources and scope
- Friedewald WT, Levy RI, Fredrickson DS. Estimation of the concentration of low-density lipoprotein cholesterol in plasma, without use of the preparative ultracentrifuge. Clin Chem 1972;18:499-502
Peer-reviewed. The original equation.
- Sampson M et al. A New Equation for Calculation of Low-Density Lipoprotein Cholesterol in Patients With Normolipidemia and/or Hypertriglyceridemia. JAMA Cardiol 2020;5:540-8
Peer-reviewed. The NIH equation constants (verified against the paper's equation image) and the 800 mg/dL limit.
- Martin SS et al. Comparison of a novel method vs the Friedewald equation for estimating LDL-C. JAMA 2013;310:2061-8
Peer-reviewed. Describes the 180-cell adjustable-factor table used by the Martin-Hopkins method.
Decision support only; it does not replace clinical judgment. The tool applies published equations and does not recommend LDL targets, treatment or medication.