Atherogenic Index of Plasma (AIP) Calculator

AIP is log₁₀ of triglycerides divided by HDL cholesterol, with both in mmol/L. Enter mg/dL instead and every answer is 0.36 too high — more than three times the width of the whole intermediate band.

Last updated 5 Sep 2026

Atherogenic Index of Plasma

log₁₀(TG ÷ HDL-C), mmol/L

Triglycerides (mmol/L)mmol/L only. A value in mg/dL must be divided by 88.57 first — 150 mg/dL is 1.69 mmol/L.

HDL cholesterol (mmol/L)mmol/L only. A value in mg/dL must be divided by 38.67 first — 40 mg/dL is 1.03 mmol/L.

0.19AIPExample

Triglycerides 1.7 mmol/L, HDL cholesterol 1.1 mmol/L

Formula

AIP = log₁₀ (triglycerides ÷ HDL cholesterol) — both in mmol/L
mmol/L = mg/dL ÷ 88.57 for triglyceride, ÷ 38.67 for cholesterol

molar concentrations: Dobiásová defined AIP on the molar ratio. Triglyceride and cholesterol have different molar masses, so the ratio itself changes with the unit and the index is not unit-independent
+0.36: computing AIP from mg/dL adds log₁₀(88.57 ÷ 38.67) = 0.36 to every answer, a constant offset rather than a scaling error, because the logarithm turns the unit ratio into an addition
log₁₀: the common logarithm, not the natural one. Using ln multiplies every result by 2.303 and makes the published bands meaningless
what it stands for: AIP tracks LDL particle size and the fractional esterification rate of cholesterol in apoB-depleted plasma. It is a surrogate for both, and measures neither

Worked example

Triglycerides 1.7 mmol/L, HDL cholesterol 1.1 mmol/L
1.7 ÷ 1.1 = 1.5455
log₁₀(1.5455) = 0.19
Between 0.11 and 0.21 → intermediate
The same sample in mg/dL is 150.6 and 42.5, giving a ratio of 3.54 and an AIP of 0.55
0.55 against 0.19 — the whole intermediate band is 0.10 wide, and the unit error is 0.36

The same patient, computed both ways

The right-hand column is not an approximation of the one before it. Because the logarithm converts the unit ratio into an addition, the mg/dL figure is always exactly 0.36 higher — and the entire distance from the bottom of the low band to the top of the intermediate one is 0.10. A mg/dL calculation puts almost everybody in the high band.
TG	HDL-C	AIP from mmol/L	AIP from mg/dL	Band it lands in
1.0 mmol/L (88.6 mg/dL)	1.5 mmol/L (58.0 mg/dL)	−0.18	0.18	Low → intermediate
1.3 mmol/L (115.1 mg/dL)	1.3 mmol/L (50.3 mg/dL)	0.00	0.36	Low → high
1.7 mmol/L (150.6 mg/dL)	1.1 mmol/L (42.5 mg/dL)	0.19	0.55	Intermediate → high
2.5 mmol/L (221.4 mg/dL)	0.9 mmol/L (34.8 mg/dL)	0.44	0.80	High → high

Bands, and what they are and are not

The bands come from Dobiásová's original work correlating log(TG/HDL-C) with directly measured lipoprotein particle size and esterification rate. They have not been adopted by any cardiovascular guideline.
AIP	Category	Reading
< 0.11	Low risk	Small dense LDL is less likely; the index does not exclude it
0.11 – 0.21	Intermediate	A band 0.10 wide, narrower than the commonest error made calculating it
> 0.21	High	Associated with small dense LDL and lower cholesterol esterification rate in the populations studied
Any value	—	Not a guideline threshold, not a treatment target, and not a substitute for a formal risk assessment or a measured apoB

A ratio inside a logarithm, and the unit that decides it

The atherogenic index of plasma is the base-10 logarithm of triglycerides divided by HDL cholesterol, with both concentrations in mmol/L. Dobiásová and Frohlich derived it as a plasma-level surrogate for two things that are difficult to measure directly: the size of LDL particles, and the fractional esterification rate of cholesterol in apoB-depleted plasma. It correlates well with both, and the conventional bands are below 0.11 for low risk, 0.11 to 0.21 for intermediate, and above 0.21 for high.

The unit is not a technicality, and this is the error the index is famous for. Triglyceride and cholesterol are different molecules with different molar masses, so the ratio between them is not the same number in mmol/L as it is in mg/dL — 88.57 against 38.67, a factor of 2.29. Because the ratio then goes inside a logarithm, that factor does not scale the answer; it adds to it. Every AIP computed from mg/dL is exactly 0.36 higher than the same patient’s AIP computed from mmol/L, whatever the values.

Set 0.36 against the bands and the problem is obvious. The whole intermediate band is 0.10 wide, and the distance from the bottom of the low-risk band to the top of the intermediate one is the same 0.10. An offset of 0.36 is more than three times that distance, so a patient calculated in mg/dL will land in the high band almost regardless of their lipids: a perfectly ordinary triglyceride of 1.3 mmol/L with an HDL of 1.3 mmol/L gives an AIP of exactly 0.00 in mmol/L and 0.36 in mg/dL. The labels on this page’s inputs name mmol/L for that reason.

What the index is worth, once it is calculated correctly, is a compact surrogate for the atherogenic dyslipidaemia of insulin resistance — high triglycerides, low HDL, small dense LDL — in a single figure derived from two tests every lipid profile already contains. What it is not is a guideline threshold, a treatment target, or a substitute for measuring apolipoprotein B, which counts the atherogenic particles directly rather than inferring their size. Treat a high AIP as a reason to assess cardiometabolic risk properly, not as a conclusion about it.

Frequently asked questions

What units does the atherogenic index of plasma use?

Both triglycerides and HDL cholesterol must be in mmol/L. The index is defined on the molar ratio. Using mg/dL adds exactly 0.36 to every result, because the logarithm turns the unit conversion into a constant offset rather than a scale factor.

What is a normal AIP?

Below 0.11 is the conventional low-risk band, 0.11 to 0.21 intermediate, and above 0.21 high. These come from Dobiásová’s original work correlating the index with lipoprotein particle size, and have not been adopted by any cardiovascular guideline.

What happens if I calculate AIP from mg/dL by mistake?

Every answer comes out 0.36 too high. The intermediate band is only 0.10 wide, so a mg/dL calculation pushes almost everyone into the high-risk band. Triglycerides of 1.3 mmol/L with an HDL of 1.3 mmol/L give 0.00 in mmol/L and 0.36 in mg/dL.

Is AIP log base 10 or natural log?

Base 10. Using the natural logarithm multiplies every result by 2.303, which makes the published bands meaningless — an AIP of 0.19 would read as 0.44.

How is AIP different from the triglyceride to HDL ratio?

It is the same ratio inside a base-10 logarithm, but the two are conventionally calculated in opposite units: the TG:HDL ratio thresholds are mg/dL figures, while AIP is defined on mmol/L. Mixing the conventions between the two is a common source of error.

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References

Dobiásová M, Frohlich J. The plasma parameter log (TG/HDL-C) as an atherogenic index: correlation with lipoprotein particle size and esterification rate in apoB-lipoprotein-depleted plasma (FER_HDL). Clin Biochem. 2001;34(7):583–588.
Dobiásová M. Atherogenic index of plasma [log(triglycerides/HDL-cholesterol)]: theoretical and practical implications. Clin Chem. 2004;50(7):1113–1115.
Fernández-Macías JC, Ochoa-Martínez AC, Varela-Silva JA, Pérez-Maldonado IN. Atherogenic index of plasma: novel predictive biomarker for cardiovascular illnesses. Arch Med Res. 2019;50(5):285–294.