LDL Cholesterol Calculator (Friedewald)

Overview

The LDL Cholesterol Calculator estimates LDL — the so-called bad cholesterol — from just three values on your lipid panel: total cholesterol, HDL cholesterol, and triglycerides, using the Friedewald equation. Most laboratories do not measure LDL directly; they calculate it with this same equation and print the result on your report, so you can use this tool to fill in a missing LDL value or check the one you were given. Results are graded against the Korean Society of Lipid and Atherosclerosis dyslipidemia guideline, alongside non-HDL cholesterol and risk-group treatment targets.

Formula

Friedewald equation (mg/dL): LDL-C = Total cholesterol − HDL-C − (Triglycerides ÷ 5)

- Triglycerides ÷ 5 = estimated VLDL cholesterol
- Valid when triglycerides < 400 mg/dL, fasting sample
- non-HDL-C = Total cholesterol − HDL-C

Classification (KSoLA, mg/dL)
- LDL-C: optimal <100 / near optimal 100–129 / borderline high 130–159 / high 160–189 / very high ≥190
- Total cholesterol: desirable <200 / borderline 200–239 / high ≥240
- HDL-C: low <40 / high (desirable) ≥60
- Triglycerides: normal <150 / borderline 150–199 / high 200–499 / very high ≥500

Targets by risk group (LDL-C / non-HDL-C, mg/dL)
- Very high risk (coronary artery disease) <55 / <85
- High risk (stroke, carotid or peripheral artery disease) <70 / <100
- Diabetes (under 10 years, no major risk factors) <100 / <130
- Moderate risk (2+ risk factors) <130 / <160
- Low risk (1 or fewer risk factors) <160 / <190

Unit conversion: divide total cholesterol, LDL, and HDL by 38.67 for mmol/L; divide triglycerides by 88.57.

How to Use

1. 1Choose the unit on your lab report — mg/dL is standard in Korea and the US, mmol/L in most of Europe and the UK.
2. 2Enter total cholesterol, HDL cholesterol, and triglycerides exactly as printed on the report.
3. 3Select your cardiovascular risk group. With no cardiovascular disease and one or fewer risk factors you are low risk.
4. 4Read your LDL value and grade, then check whether non-HDL cholesterol clears your risk-group target.
5. 5If triglycerides are 400 mg/dL or higher the equation does not apply — use a direct LDL assay or non-HDL cholesterol instead.

Examples

Background

The Friedewald equation was published in 1972 by Friedewald, Levy, and Fredrickson and rests on the empirical observation that, in a fasting sample, VLDL cholesterol is roughly one fifth of the triglyceride concentration. Laboratories worldwide have used it as the default for over fifty years, which is why the LDL number on most lipid panels is a calculated value rather than a direct measurement. It breaks down above 400 mg/dL of triglycerides, where the TG/5 assumption no longer holds, and it also tends to underestimate LDL when triglycerides run 150–400 mg/dL and LDL is low — the reason newer equations such as Martin-Hopkins and direct assays exist. The grading bands and risk-group targets here follow the Korean Society of Lipid and Atherosclerosis dyslipidemia guideline, which sets an LDL target below 55 mg/dL for coronary artery disease and defines each non-HDL target as the LDL target plus 30 mg/dL.

Tips

• ✔Fast for 9–12 hours before a lipid panel. Eating beforehand raises triglycerides and pushes the calculated LDL lower than it really is.
• ✔If your triglycerides run high, non-HDL cholesterol is the steadier number to watch — it is just total cholesterol minus HDL and has no validity limit.
• ✔Remember non-HDL targets as the LDL target plus 30 mg/dL (an LDL goal of under 100 means non-HDL under 130).
• ✔HDL of 60 mg/dL or above counts as a protective factor and removes one item from your risk-factor tally.
• ✔Judge the trend across at least two tests rather than a single value — acute illness, pregnancy, and weight change all move lipid numbers substantially.

FAQ