# What is my LDL cholesterol?

Estimates LDL cholesterol from total cholesterol, HDL cholesterol, and triglycerides with the Friedewald or the Sampson (NIH) equation, in mg/dL or mmol/L, and shows its NCEP ATP III category.

- Page: https://www.acalculator.org/health/ldl-calculator
- JSON spec: https://www.acalculator.org/health/ldl-calculator.json
- Version: 4151adcecc13

## Default answer

Example with the default inputs (Units mg/dL, Equation Friedewald, Total cholesterol (mg/dL) 200, HDL cholesterol (mg/dL) 50, Triglycerides (mg/dL) 150): The estimated LDL cholesterol is 120 mg/dL (3.1 mmol/L): Near or above optimal (100 to 129 mg/dL).

## Inputs

| Key | Label | Description |
| --- | --- | --- |
| units | Units | US units (mg/dL) or SI units (mmol/L). |
| method | Equation | Friedewald (1972), for triglycerides under 400 mg/dL, or Sampson NIH equation 2 (2020), for triglycerides up to 800 mg/dL. |
| tc | Total cholesterol (mg/dL) | Total cholesterol, 50 to 1,000 mg/dL. |
| tcSi | Total cholesterol (mmol/L) | Total cholesterol, 1.3 to 25.9 mmol/L. |
| hdl | HDL cholesterol (mg/dL) | HDL ("good") cholesterol, 5 to 200 mg/dL. |
| hdlSi | HDL cholesterol (mmol/L) | HDL ("good") cholesterol, 0.13 to 5.17 mmol/L. |
| tg | Triglycerides (mg/dL) | Triglycerides, 10 to 3,000 mg/dL. |
| tgSi | Triglycerides (mmol/L) | Triglycerides, 0.11 to 33.9 mmol/L. |

## Outputs

| Key | Label | Description |
| --- | --- | --- |
| ldl | LDL cholesterol (mg/dL) | The estimated LDL cholesterol, in mg/dL, to a whole number. |
| ldlSi | LDL cholesterol (mmol/L) | The same estimate in mmol/L (mg/dL × 0.02586), to 2 decimals. |
| category | ATP III category | The NCEP ATP III band of the LDL value. |
| nonHdl | Non-HDL cholesterol (mg/dL) | Total cholesterol minus HDL cholesterol, in mg/dL, to a whole number. |
| nonHdlSi | Non-HDL cholesterol (mmol/L) | Total cholesterol minus HDL cholesterol, in mmol/L, to 2 decimals. |

## Method

Friedewald: LDL = TC − HDL − TG ÷ 5 (mg/dL, TG under 400). Sampson NIH equation 2: LDL = TC/0.948 − HDL/0.971 − (TG/8.56 + TG × non-HDL/2140 − TG²/16100) − 9.44 (mg/dL, TG up to 800). SI values convert with 0.02586 (cholesterol) and 0.0113 (triglycerides) mmol/L per mg/dL.

## Assumptions

- Total cholesterol, HDL cholesterol, and triglycerides come from the same blood sample.
- The LDL estimate is worked from the exact typed values and rounded once: to a whole mg/dL, and to 2 decimals in mmol/L.
- The ATP III category is read from the whole mg/dL value shown.

## Worked examples

1. units = us, method = friedewald, tc = 200, hdl = 50, tg = 150 gives ldl = 120, ldlSi = 3.1, category = Near or above optimal (100 to 129 mg/dL), nonHdl = 150, nonHdlSi = 3.88. Source: Friedewald 1972: 200 − 50 − 150 ÷ 5 = 120 mg/dL.
2. units = us, method = sampson, tc = 200, hdl = 50, tg = 150 gives ldl = 123, ldlSi = 3.19, category = Near or above optimal (100 to 129 mg/dL). Source: Sampson 2020 NIH equation 2: 210.970 − 51.493 − (17.523 + 10.514 − 1.398) − 9.44 = 123.397 mg/dL.
3. units = us, method = sampson, tc = 260, hdl = 35, tg = 500 gives ldl = 133, ldlSi = 3.45, category = Borderline high (130 to 159 mg/dL), nonHdl = 225. Source: Sampson 2020 NIH equation 2 = 133.323 mg/dL.
4. units = us, method = friedewald, tc = 240, hdl = 40, tg = 300 gives ldl = 140, ldlSi = 3.62, category = Borderline high (130 to 159 mg/dL), nonHdl = 200. Source: Friedewald 1972: 240 − 40 − 60 = 140 mg/dL.
5. units = si, method = friedewald, tcSi = 5.2, hdlSi = 1.3, tgSi = 1.7 gives ldl = 121, ldlSi = 3.12, nonHdlSi = 3.9.

## FAQ

### How is LDL cholesterol calculated?

Most lab reports estimate it. The Friedewald equation takes total cholesterol, subtracts HDL cholesterol, and subtracts triglycerides ÷ 5 (all in mg/dL). The newer Sampson (NIH) equation uses the same three values with a different formula.

### Which equation should I pick?

Friedewald is the classic equation and does not apply when triglycerides are 400 mg/dL or more. Sampson et al. (2020) found their NIH equation 2 more accurate than Friedewald, with good results for triglycerides up to 800 mg/dL.

### What is a good LDL cholesterol level?

The NCEP ATP III report grades LDL under 100 mg/dL as optimal, 100 to 129 as near or above optimal, 130 to 159 as borderline high, 160 to 189 as high, and 190 or more as very high. Your own goal depends on your overall risk.

### Why does the page refuse triglycerides of 400 or more with Friedewald?

The equation treats triglycerides ÷ 5 as the cholesterol carried by very low density lipoproteins. That estimate fails when triglycerides are high, so labs do not report a Friedewald LDL then.

### What is non-HDL cholesterol?

It is total cholesterol minus HDL cholesterol: all the cholesterol in particles other than HDL. The page shows it next to the LDL estimate.

### Can I enter values in mmol/L?

Yes. Pick mmol/L. The page converts cholesterol with 0.02586 mmol/L per mg/dL and triglycerides with 0.0113 mmol/L per mg/dL, works the equation in mg/dL, and shows the result in both units.

## Sources

- 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(6):499-502. https://doi.org/10.1093/clinchem/18.6.499 (retrieved 2026-10-05)
- Sampson M, Ling C, Sun Q, et al. A new equation for calculation of low-density lipoprotein cholesterol in patients with normolipidemia and/or hypertriglyceridemia. JAMA Cardiol. 2020;5(5):540-548. https://doi.org/10.1001/jamacardio.2020.0013 (open at https://pmc.ncbi.nlm.nih.gov/articles/PMC7240357/, retrieved 2026-10-05)
- The NIH equation 2 written out in text: Assessing the practical differences in LDL-C estimates calculated by Friedewald, Martin/Hopkins, or NIH equation 2. https://pmc.ncbi.nlm.nih.gov/articles/PMC10548185/ (retrieved 2026-10-05)
- Expert Panel on Detection, Evaluation, and Treatment of High Blood Cholesterol in Adults. Executive summary of the third report of the National Cholesterol Education Program (NCEP) Adult Treatment Panel III. JAMA. 2001;285(19):2486-2497. https://doi.org/10.1001/jama.285.19.2486 (retrieved 2026-10-05)
- Nelson RH. Hyperlipidemia as a risk factor for cardiovascular disease. Prim Care. 2013;40(1):195-211. Table 1 reproduces the ATP III classification of LDL, total, and HDL cholesterol and triglycerides. https://pmc.ncbi.nlm.nih.gov/articles/PMC3572442/ (retrieved 2026-10-05)