LDL to HDL Ratio Calculator
LDL to HDL Ratio Calculator
Divide LDL cholesterol by HDL cholesterol for a unit-independent ratio — widely quoted, useful for explanation, and used by no major guideline as a treatment target.
LDL to HDL Ratio
LDL ÷ HDL → ratioLDL cholesterol 132 mg/dL, HDL cholesterol 48 mg/dL
Formula
Both terms are cholesterol, so the units cancel.
- dimensionless
- the ratio is identical in mg/dL and mmol/L, because both terms convert with the same factor of 0.0259
- LDL
- calculated or directly measured; a calculated LDL carries the assumptions of whichever equation produced it
- not a target
- no major guideline sets a ratio goal; LDL, non-HDL cholesterol and apolipoprotein B are the targets in current use
Worked example
LDL cholesterol 132 mg/dL, HDL cholesterol 48 mg/dL
132 ÷ 48 = 2.75
Between 2 and 3.5 on the conventional bands → average
The same values in mmol/L — 3.41 and 1.24 — give the same 2.75, to within rounding
Conventional bands, and the value pairs that produce them
| Ratio | Description commonly used | Example pair (mg/dL) |
|---|---|---|
| < 2.0 | Desirable | LDL 90, HDL 50 |
| 2.0 – 3.5 | Average | LDL 132, HDL 48 |
| 3.5 – 5.0 | Elevated | LDL 160, HDL 40 |
| > 5.0 | High | LDL 170, HDL 30 |
One ratio, four different patients
| LDL | HDL | Ratio | Reading |
|---|---|---|---|
| 132 mg/dL | 48 mg/dL | 2.75 | The default example: an average ratio at an above-optimal LDL |
| 3.41 mmol/L | 1.24 mmol/L | 2.75 | The identical sample in SI units — the ratio does not change |
| 110 mg/dL | 40 mg/dL | 2.75 | Same ratio, lower LDL, lower HDL |
| 220 mg/dL | 80 mg/dL | 2.75 | Same ratio at an LDL that would prompt assessment for familial hypercholesterolaemia |
Unit-independent, easy to explain, and not a treatment target
Both terms of this ratio are cholesterol concentrations measured by the same assay principle, so the units cancel and the answer is identical in mg/dL and in mmol/L. That is worth stating because the neighbouring triglyceride to HDL ratio behaves differently: triglyceride and cholesterol convert between mass and molar units with different factors, so that ratio changes by about 2.3-fold between units and its thresholds apply only to mg/dL. This one can be quoted safely from a report in either system.
The bands in common use — desirable below 2, average to about 3.5, elevated to 5 and high above it — are conventions drawn from the lipid ratio literature and laboratory commentary. They are not guideline thresholds. No major guideline uses the LDL to HDL ratio to decide whether or how to treat, and it should not be presented as though a consensus stood behind those numbers.
There is a specific reason the ratio has fallen out of use as a target. It can improve because HDL rose, and raising HDL pharmacologically has repeatedly failed to reduce cardiovascular events: niacin and the cholesteryl ester transfer protein inhibitors raised HDL substantially, moved every ratio in the right direction, and did not deliver the outcome benefit that movement implied. A ratio can therefore improve without any benefit at all, which is a fatal property in a treatment target.
Guidelines have moved instead to absolute LDL and non-HDL cholesterol targets, and increasingly to apolipoprotein B, which counts atherogenic particles rather than the cholesterol they carry. What survives of the ratio is its value as a communication tool: it puts the two numbers into one figure a patient can hold on to, and it makes the point that a low HDL matters. Used that way it is harmless. Used as a target it hides the values that produced it — an LDL of 220 with an HDL of 80 gives the same 2.75 as an LDL of 110 with an HDL of 40, and the two patients need entirely different management.
Frequently asked questions
What is a good LDL to HDL ratio?
Figures below 2 are conventionally described as desirable and figures above 5 as high, with 2 to 3.5 described as average. These are conventions from the ratio literature rather than guideline thresholds.
Is there a guideline target for the LDL to HDL ratio?
No. No major cholesterol guideline uses this ratio for treatment decisions. Targets are set on LDL cholesterol, non-HDL cholesterol or apolipoprotein B, all of which are absolute concentrations.
Does the ratio change between mg/dL and mmol/L?
No. Both terms are cholesterol and convert with the same factor, so the units cancel. This is unlike the triglyceride to HDL ratio, which is about 2.3 times smaller in mmol/L and whose thresholds apply only to mg/dL.
Can the ratio improve without any benefit?
Yes, and this is the main criticism of it. A ratio falls if HDL rises, but raising HDL with niacin or with cholesteryl ester transfer protein inhibitors improved the ratio without reducing cardiovascular events.
Should I use the ratio or the absolute LDL?
Use the absolute LDL, or non-HDL cholesterol, for any decision. The ratio is useful mainly for explaining to a patient why a low HDL matters alongside a raised LDL.
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References
- Millán J, Pintó X, Muñoz A, et al. Lipoprotein ratios: physiological significance and clinical usefulness in cardiovascular prevention. Vasc Health Risk Manag. 2009;5:757–765.
- Grundy SM, Stone NJ, Bailey AL, et al. 2018 AHA/ACC multisociety guideline on the management of blood cholesterol. Circulation. 2019;139(25):e1082–e1143.
- Expert Panel on Detection, Evaluation, and Treatment of High Blood Cholesterol in Adults. Third Report of the National Cholesterol Education Program (NCEP) Expert Panel (Adult Treatment Panel III) final report. Circulation. 2002;106(25):3143–3421.
Medical Disclaimer: The tools and content provided here are for educational and reference purposes only. They are not intended to substitute for professional medical advice, diagnosis, or treatment. Clinical decisions should always be based on the comprehensive assessment of a qualified healthcare professional.