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Calculated LDL Cholesterol (Friedewald & NIH)

Estimate LDL cholesterol from a standard lipid panel using the Friedewald and NIH (Sampson) equations.

For healthcare professionalsHeart & blood vesselsv1.0.1

For healthcare professionals / clinical use. Not a self-diagnosis tool.

Your measurements

Calculated on your device. Nothing is sent to a server.

Your result will appear here

Enter your measurements, then press Calculate.

Methodology

Friedewald (1972); NIH/Sampson (2020)

Friedewald: TC − HDL − TG/5; Sampson: TC/0.948 − HDL/0.971 − (TG/8.56 + TG×nonHDL/2140 − TG²/16100) − 9.44 (mg/dL)

The NIH equation is more accurate than Friedewald at high triglycerides and low LDL. Both need TC, HDL and triglycerides in mg/dL. The 2026 ACC/AHA guideline prefers the Martin/Hopkins or NIH equation over Friedewald.

Who it is for
Adults with a standard lipid panel; triglycerides below 800 mg/dL (9 mmol/L).
Version
1.0.1

How this calculator works

Where the formula comes from

  • Friedewald, Levy and Fredrickson (1972) estimated LDL cholesterol without ultracentrifugation as total cholesterol minus HDL minus triglycerides ÷ 5, where triglycerides ÷ 5 estimates VLDL cholesterol (mg/dL).[1]
  • The NIH (Sampson) equation was derived in 2020 from 8,656 patients at the NIH Clinical Center using LDL cholesterol measured by beta-quantification.[2]

The inputs

  • Both equations use total cholesterol, HDL cholesterol and triglycerides from a standard lipid panel; the published constants are for mg/dL.[1][2]
  • The NIH equation was developed to improve LDL cholesterol estimation, including for triglycerides of 400–800 mg/dL where Friedewald is not valid; its performance varies with triglyceride and LDL cholesterol levels.[2]

Versions and alternatives

  • The Martin/Hopkins method (2013) replaces the fixed factor of 5 with an adjustable factor based on triglycerides and non-HDL cholesterol.[3]

Where accuracy falls (published evidence)

  • Friedewald is not used when triglycerides are 400 mg/dL or more or in type III hyperlipoproteinaemia.[1]
  • Friedewald becomes less accurate at low LDL cholesterol, particularly below 70 mg/dL.[4]

What guidelines say

  • The 2018 AHA/ACC cholesterol guideline says that when LDL cholesterol is below 70 mg/dL, direct measurement or a modified estimate (Martin/Hopkins) is reasonable to improve accuracy over Friedewald.[4]
  • The 2026 ACC/AHA dyslipidaemia guideline prefers the Martin/Hopkins or NIH (Sampson) equation over Friedewald for estimating LDL cholesterol.[5]

Sources

  1. 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. doi:10.1093/clinchem/18.6.499
  2. 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. doi:10.1001/jamacardio.2020.0013
  3. Martin SS, Blaha MJ, Elshazly MB, et al. Comparison of a novel method vs the Friedewald equation for estimating low-density lipoprotein cholesterol levels from the standard lipid profile. JAMA. 2013;310(19):2061–2068. doi:10.1001/jama.2013.280532
  4. Grundy SM, Stone NJ, Bailey AL, et al. 2018 AHA/ACC/AACVPR/AAPA/ABC/ACPM/ADA/AGS/APhA/ASPC/NLA/PCNA Guideline on the Management of Blood Cholesterol. Circulation. 2019;139(25):e1082–e1143. doi:10.1161/CIR.0000000000000625
  5. 2026 ACC/AHA/AACVPR/ABC/ACPM/ADA/AGS/APhA/ASPC/NLA/PCNA Guideline on the Management of Dyslipidemia. Circulation. 2026. doi:10.1161/CIR.0000000000001423

Compiled from the published sources above. Every statement was agreed independently by three AI research tools (Claude, ChatGPT, DeepSeek) and its source verified in PubMed or Crossref by the Hakeemly editorial team. Not reviewed by a doctor unless stated. Agreed on

Worked example: how to calculate calculated LDL

Inputs

Total cholesterol
200 mg/dL
HDL cholesterol
50 mg/dL
Triglycerides
150 mg/dL

Result

NIH equation (Sampson 2020)
123 mg/dL
Friedewald (1972)
120 mg/dL

An illustration with sample values, worked out with the same method the tool above uses.

Limitations

  • Friedewald is not used at triglycerides of 400 mg/dL or more or in type III hyperlipoproteinaemia. The NIH equation was validated for triglycerides up to 800 mg/dL and is not applied above that.

References

  1. 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. doi:10.1093/clinchem/18.6.499
  2. 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. doi:10.1001/jamacardio.2020.0013
  3. 2026 ACC/AHA/AACVPR/ABC/ACPM/ADA/AGS/APhA/ASPC/NLA/PCNA Guideline on the Management of Dyslipidemia. Circulation. 2026. doi:10.1161/CIR.0000000000001423

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