Cholesterol Ratio Calculator
A Ratio That Reads Differently Than Either Number Alone
Total cholesterol and HDL ("good") cholesterol each tell part of the story, but the ratio between them is what many cardiovascular risk assessments actually use, since a high total cholesterol paired with high HDL reads very differently than the same total paired with low HDL. This calculator produces that ratio directly, and can estimate LDL from triglycerides when it isn't measured separately.
The Formula
Risk Categories
| TC/HDL ratio | Category |
|---|---|
| Below 3.5 | Optimal / Low Risk |
| 3.5 – 5.0 | Average Risk |
| Above 5.0 | High Risk |
Estimating LDL When It Isn't Given
LDL = Total Cholesterol − HDL − (Triglycerides ÷ 5) (mg/dL, divisor 2.2 for mmol/L)
This estimate is only valid when triglycerides are below 400 mg/dL (4.5 mmol/L) — above that threshold, the Friedewald formula becomes unreliable and the calculator flags the LDL estimate as unavailable rather than returning an inaccurate figure.
Why the Ratio Gets Used Alongside Raw Numbers
- Routine cardiovascular screening — the TC/HDL ratio is one of several figures reviewed alongside individual cholesterol values during a standard lipid panel review.
- Comparing HDL's protective effect — because HDL helps clear cholesterol from the bloodstream, a favorable ratio can occur even with a moderately elevated total cholesterol, if HDL is also high.
- Tracking change over time — watching the ratio trend across repeat lipid panels can be more informative than any single reading.
How to Use This Calculator
- Select your unit: mg/dL or mmol/L.
- Enter your total cholesterol and HDL values.
- Optionally enter LDL directly, or enter triglycerides to estimate LDL via the Friedewald formula.
- Select Calculate to see your TC/HDL ratio, risk category, and LDL/HDL ratio if available.
Related Calculations
Check blood pressure alongside cholesterol with the Blood Pressure Calculator, or overall lifestyle risk factors with the Life Expectancy Calculator.