LDL Cholesterol Calculator (Friedewald Equation)
Estimated LDL cholesterol from total cholesterol, HDL and triglycerides in mg/dL or mmol/L, with non-HDL cholesterol and the NCEP band.
Results
What this tool does
Most routine lipid panels do not measure LDL directly but calculate it with the Friedewald equation of 1972: LDL = total − HDL − triglycerides ÷ 5 in mg/dL, or ÷ 2.2 in mmol/L. The triglyceride term stands in for the cholesterol carried by VLDL particles, an assumption that fails when triglycerides reach about 400 mg/dL (4.5 mmol/L), and it tends to underestimate LDL when LDL is already low. Newer equations (Martin–Hopkins, Sampson) and direct assays do better there. The bands shown are the 2001 NCEP ATP III ones; today's guidelines set targets by overall cardiovascular risk, so your own target may differ.
Formula
LDL = total − HDL − triglycerides ÷ 5 (mg/dL) · LDL = total − HDL − triglycerides ÷ 2.2 (mmol/L) · non-HDL = total − HDL
Variables
| Symbol | Meaning | Unit |
|---|---|---|
tc | Total cholesterol | — |
hd | HDL cholesterol | — |
tg | Triglycerides | — |
un | Unit of the three values | — |
LD | Estimated LDL cholesterol (Friedewald) | — |
NH | Non-HDL cholesterol | — |
RT | Total cholesterol ÷ HDL | — |
BD | LDL band (NCEP ATP III) | — |
VL | Is the Friedewald estimate reliable? | — |
Worked example
- Total cholesterol200
- HDL cholesterol55
- Triglycerides130
- Unit of the three values1
- Estimated LDL cholesterol (Friedewald)119.0
- Non-HDL cholesterol145.0
- Total cholesterol ÷ HDL3.6
- LDL band (NCEP ATP III)Near optimal — 100–129 mg/dL (2.6–3.3 mmol/L)
- Is the Friedewald estimate reliable?Yes — triglycerides are below 400 mg/dL (4.5 mmol/L)
Limitations
- This tool is informational only. It does not diagnose, treat or replace a qualified health professional. Speak to a doctor before making decisions about your health.
- For work that must comply with a standard or be signed off, check the result against the applicable code and have it reviewed by a qualified engineer.