LDL Cholesterol Calculator

Estimate your LDL cholesterol from total cholesterol, HDL, and triglycerides using the Sampson-NIH 2020 equation, with the classic Friedewald estimate shown alongside for comparison. Supports mg/dL and mmol/L. This is an informational reference using published formulas, not a diagnostic test.

Units

Total cholesterol

mg/dL

HDL cholesterol

mg/dL

Triglycerides

mg/dL

Estimated LDL-C (Sampson-NIH)

Both estimates are calculated, not directly measured. The Sampson-NIH equation is valid up to triglycerides of 800 mg/dL; Friedewald becomes unreliable above about 400 mg/dL and is shown only for comparison. A direct LDL measurement is recommended when triglycerides are very high. Discuss your lipid results with a healthcare provider.

Tracking your cholesterol? See your LDL, HDL, and triglyceride trends over time in the Health3 app.

How LDL Cholesterol Is Estimated

On most lab reports, LDL cholesterol is not measured directly. It is calculated from the three values a standard lipid panel does measure: total cholesterol, HDL cholesterol, and triglycerides. For decades the Friedewald equation (1972) was the default, but it systematically underestimates LDL at low LDL levels and breaks down when triglycerides are high. In 2020, Sampson and colleagues at the NIH published a more accurate equation (JAMA Cardiology 5:540–548) that remains valid up to triglycerides of 800 mg/dL. This tool computes both so you can see them side by side.

Sampson-NIH (2020), mg/dL:
LDL = TC/0.948 − HDL/0.971 − (TG/8.56 + TG×(TC−HDL)/2140 − TG²/16100) − 9.44

Friedewald (1972), shown for comparison:
LDL = TC − HDL − TG/5 (mg/dL) or TC − HDL − TG/2.2 (mmol/L)

Published LDL Reference Context

The bands below reflect the LDL-C categories long used by the US National Cholesterol Education Program (NCEP ATP III). These are published reference categories, not a treatment plan; current guidelines individualise LDL goals by overall cardiovascular risk.

LDL-C (mg/dL)	LDL-C (mmol/L)	NCEP ATP III category
Below 100	Below 2.6	Optimal
100 – 129	2.6 – 3.3	Near or above optimal
130 – 159	3.4 – 4.1	Borderline high
160 – 189	4.1 – 4.9	High
190 and above	4.9 and above	Very high

When a Calculated LDL Can Be Misleading

Very high triglycerides. Above 800 mg/dL even the Sampson equation is not validated, and a direct LDL measurement is preferred.
Non-fasting samples. Triglycerides rise after eating, which shifts the calculated LDL. Many labs still prefer a fasting sample for the calculated value.
Low LDL. Friedewald in particular underestimates LDL when it is low, which is exactly where treatment targets often sit; the Sampson equation was designed to fix this.

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Frequently Asked Questions

What is the difference between the Sampson and Friedewald LDL equations?

Both estimate LDL cholesterol from total cholesterol, HDL, and triglycerides because LDL is usually not measured directly. The Friedewald equation (1972) uses LDL = TC - HDL - TG/5, but it underestimates LDL at low levels and is unreliable when triglycerides exceed about 400 mg/dL. The Sampson-NIH equation (2020) is more accurate, especially at low LDL and high triglycerides, and is valid up to 800 mg/dL of triglycerides. This tool shows both.

Is calculated LDL accurate?

For most people with normal triglycerides, a calculated LDL is close to a directly measured value, and the Sampson-NIH equation improves accuracy further. Accuracy falls when triglycerides are high or the sample is non-fasting. When triglycerides are very high (above 800 mg/dL) a direct LDL measurement is preferred. A calculated LDL is a reference estimate, not a diagnosis.

Do I need to fast before the lipid panel?

Many guidelines now accept non-fasting lipid panels for general screening, but triglycerides (and therefore any calculated LDL) are more stable after an 8 to 12 hour fast. If your lab asked you to fast, use the fasting values here. If you are unsure, note that a non-fasting sample can shift the calculated LDL.

What LDL level should I aim for?

There is no single target for everyone. Current guidelines set LDL goals based on your overall cardiovascular risk, so someone with diabetes or established heart disease typically has a lower target than someone at low risk. The NCEP categories shown here are published reference bands, not personal goals. Discuss the right target for you with your healthcare provider.

Can I enter mmol/L values?

Yes. Switch the unit toggle to mmol/L. The Sampson equation is defined in mg/dL, so the calculator converts your cholesterol values (x 38.67) and triglycerides (x 88.57) to mg/dL, computes both estimates, and displays the result back in your chosen unit.

Medical Disclaimer: This tool estimates LDL cholesterol using published equations (Sampson SL, et al. JAMA Cardiol. 2020;5(5):540–548; Friedewald WT, et al. Clin Chem. 1972;18(6):499–502). A calculated LDL is a reference estimate, not a direct measurement or a diagnosis, and can be inaccurate when triglycerides are high or the sample is non-fasting. The NCEP reference categories shown are general published bands, not personal treatment targets. This tool is for informational and educational use only. Always consult a qualified healthcare provider to interpret your lipid results.

Track Your Lipid Panel Over Time

Health3 logs your LDL, HDL, total cholesterol, triglycerides, and 50+ other biomarkers, shows trends, and keeps your lab reports in one place.