Cholesterol Ratio Calculator

How to use this calculator

1. Switch units to match your lab printout. US labs report in mg/dL; UK, EU, Canada, and Australia report in mmol/L. The toggle at the top converts every input and every output number on the fly — no separate page, no rerun.
2. Enter your four lipid values. Total cholesterol and HDL are required. LDL is optional — if you leave it blank and enter triglycerides, the tool backfills LDL using the Friedewald equation (valid up to 400 mg/dL TG). Triglycerides unlock the TG/HDL ratio and the Atherogenic Index of Plasma.
3. Set your sex. AHA targets for the TC/HDL and LDL/HDL ratios differ between men and women — the chips and explainer copy adjust accordingly.
4. Read the five chips. Each metric returns a value plus an AHA-cited band. The card outline takes the color of your worst tier across all five metrics, because that's the marker driving your overall lipid risk picture.
5. Save the panel to your log. Optional — entries stay on your device. Track lipids across a 6-month statin trial, a low-carb diet, or a fish-oil intervention, then export a one-page PDF with all five metrics for your clinician.

Why this calculator is different from other cholesterol ratio tools

Most cholesterol ratio calculators online compute one or two ratios and stop there. They use generic "ideal/good/bad" labels with no guideline citation, default to mg/dL with no live unit toggle, and reset every time you refresh the page. Here's what this tool does differently:

• All five lipid metrics, in one place. Total/HDL, LDL/HDL, TG/HDL, non-HDL cholesterol, and the Atherogenic Index of Plasma. The AHA's preferred secondary target after LDL is non-HDL cholesterol, not a ratio — most calculators skip it. AIP (log10[TG/HDL]) is a calculated marker of small-dense LDL particle burden that even fewer calculators ship.
• AHA-cited risk bands, sex- and age-aware. Every chip names the underlying source — the 2018 AHA/ACC Cholesterol Guideline, the Castelli risk indices, Dobiasova's AIP paper, Murguia-Romero on TG/HDL — instead of generic "good/bad" labels. Targets for men and women differ in places (women's HDL norms, LDL/HDL cutoffs); the tool adjusts.
• Friedewald LDL backfill, with a guardrail. If you don't know your LDL but you have TC, HDL, and TG, the tool fills in LDL using the Friedewald equation (LDL ≈ TC − HDL − TG/5, mg/dL). When triglycerides exceed 400 mg/dL the equation is unreliable — instead of returning a wrong number, the tool warns you to ask for a direct LDL-C measurement.
• Live mg/dL ↔ mmol/L toggle. Hit the unit switch and every input value, every result chip, and every reference band converts on the fly. Useful for international users, useful for US users translating an old printout from a hospital that reported in mmol/L.
• Save panels and export a clinician-ready PDF. Most calculators reset on refresh. Your log stays on your device, and the one-click PDF export carries all five metrics, the worst-tier classification per panel, the date range, the cited references, and Dr. Taylor's byline — the kind of document a clinician can drop straight into a chart.
• Embeddable widget for educators. Primary care educators, registered dietitians, lipid clinics, and patient-education sites can copy a one-line snippet and host this calculator (with attribution baked in) on their own pages. There's no fee, no signup, no analytics attached.
• Reviewed by a named clinician. Most calculator-shaped pages on this SERP are anonymous tool factories. This one is reviewed by Dr. David Taylor, MD, PhD, with cited sources for every formula and every band.

How this calculator works (the math)

Five formulas, all client-side, all auditable. No server round-trips, no API calls, no analytics tracking your numbers.

Total Cholesterol / HDL ratio (Castelli I)

The most-cited cardiovascular risk ratio:

TC/HDL = TC ÷ HDL

AHA-cited targets per Castelli's Framingham work (Castelli WP, Am J Med 1984): under 3.5 is optimal; 3.5–5.0 is acceptable; above 5.0 is high. Women's targets are slightly tighter — see the in-tool chip for sex-specific bands.

LDL / HDL ratio (Castelli II)

Direct lipoprotein-quality ratio:

LDL/HDL = LDL ÷ HDL

Castelli II targets (Castelli 1988): for men, under 1.0 is ideal, 1.0–3.5 average, above 3.5 high. Women's bands are slightly different again.

Triglyceride / HDL ratio

A surrogate marker for insulin resistance and small-dense LDL particle burden:

TG/HDL = TG ÷ HDL

TG/HDL targets depend on units. In mg/dL: under 2.0 is ideal, 2.0–4.0 borderline, above 4.0 high. In mmol/L: under 0.87 ideal, 0.87–1.74 borderline, above 1.74 high. Per Murguia-Romero et al. 2013, J Lipid Res.

Non-HDL cholesterol

The AHA's preferred secondary target after LDL — captures LDL plus all the other atherogenic particles (VLDL, IDL, Lp(a)):

Non-HDL = TC − HDL

Per the 2018 AHA/ACC/AACVPR/AAPA/ABC/ACPM/ADA/AGS/APhA/ASPC/NLA/PCNA Guideline on the Management of Blood Cholesterol: under 130 mg/dL is desirable; under 100 mg/dL is optimal in adults with established ASCVD or diabetes.

Atherogenic Index of Plasma (AIP)

A logarithmic ratio that better predicts small-dense LDL particle burden than any single number alone:

AIP = log10(TG / HDL)

Per Dobiasova's original paper (Dobiasova M & Frohlich J, Clin Biochem 2001;34:583–588), AIP requires both values in molar units (mmol/L). For mg/dL inputs, this calculator converts internally using the molar-mass factor 38.67 / 88.57 = 0.4366 before taking the logarithm. AIP bands per Dobiasova 2011: under 0.11 is low cardiovascular risk; 0.11–0.21 intermediate; above 0.21 high risk.

Friedewald LDL backfill

If you didn't get an LDL reading on your panel — common with older or non-fasting panels — the tool estimates LDL from the other three numbers using the Friedewald equation (Friedewald, Levy & Fredrickson, Clin Chem 1972):

LDL ≈ TC − HDL − TG / 5 (mg/dL)

Friedewald is unreliable when triglycerides exceed 400 mg/dL; in that case, the tool surfaces a warning instead of returning a guess. Newer estimating equations (Martin-Hopkins, Sampson) handle high-TG cases better and are on the roadmap for v2.

Three real-world examples

Healthy mid-life adult — what "optimal" looks like

Marcus is 48, male, with a recent panel: TC 180, HDL 70, LDL 90, TG 100 (mg/dL). His TC/HDL is 2.57 (optimal), LDL/HDL is 1.29 (optimal), TG/HDL is 1.43 (optimal), non-HDL is 110 mg/dL (desirable), AIP is −0.21 (low risk). All five chips return green. The card outlines green. The conversation with his primary care doctor is a maintenance one — annual panel, keep the Mediterranean-pattern eating, keep the four 30-minute walks per week, no statin discussion warranted yet.

Borderline lipid panel — the conversation to have with a clinician

Eleanor is 52, female, in early peri-menopause: TC 230, HDL 55, LDL 145, TG 140 (mg/dL). TC/HDL is 4.18 (good for women, but at the borderline edge), LDL/HDL is 2.64 (above women's "ideal" of 1.5), TG/HDL is 2.55 (borderline), non-HDL is 175 (borderline-high), AIP is +0.05 (low risk). The card outlines amber because of the non-HDL chip. The conversation with her clinician is a real one: 10-year ASCVD risk calculation, family history review, and a 3–6 month trial of soluble fiber (a psyllium-based supplement moves LDL down 5–10% in most adults) plus more aerobic activity. If non-HDL hasn't moved at the next panel, statin therapy enters the discussion. Eleanor saves this panel to the log so the comparison panel in 6 months sits next to it on the PDF she brings to her appointment.

Statin-managed adult — when ratios mask underlying risk

Robert is 62, male, on rosuvastatin 10 mg for two years. His on-statin panel: TC 150, HDL 42, LDL 80, TG 180 (mg/dL). TC/HDL is 3.57 (optimal-good), LDL/HDL is 1.90 (good), TG/HDL is 4.29 (high), non-HDL is 108 (desirable for ASCVD-target), AIP is +0.27 (high risk). Three chips green, two chips red. The card outlines red because of the TG/HDL and AIP markers. This is a useful pattern to recognize: statins move LDL aggressively but do less for triglycerides and HDL, so a "looks-good" LDL number can hide an unfavorable TG/HDL and AIP picture driven by insulin resistance. The conversation with Robert's cardiologist is about adding a high-purity omega-3 (REDUCE-IT 2018), a fiber supplement, and a structured carbohydrate-quality intervention. CoQ10 supplementation is also frequently discussed in statin users (statin-associated myalgia, depleted mitochondrial CoQ10) — the evidence is mixed, but the downside is low.

What "good cholesterol ratios" look like — full reference table

AHA-cited bands by metric, sex (where applicable), and unit:

Total Cholesterol / HDL ratio (Castelli I)

• Men: < 3.5 optimal · 3.5–5.0 good · 5.0–9.5 moderate-high · > 9.5 high
• Women: < 3.5 optimal · 3.5–4.4 good · 4.4–7.0 moderate-high · > 7.0 high

LDL / HDL ratio (Castelli II)

• Men: < 1.0 ideal · 1.0–3.5 average · > 3.5 high
• Women: < 1.5 ideal · 1.5–3.2 average · > 3.2 high

Triglyceride / HDL ratio

• mg/dL: < 2.0 ideal · 2.0–4.0 borderline · 4.0–6.0 high · > 6.0 very high
• mmol/L: < 0.87 ideal · 0.87–1.74 borderline · 1.74–2.62 high · > 2.62 very high

Non-HDL cholesterol

• mg/dL: < 100 (ASCVD/diabetes target) · 100–129 desirable · 130–159 borderline-high · 160–189 high · ≥ 190 very high
• mmol/L: < 2.6 · 2.6–3.3 · 3.4–4.1 · 4.2–4.9 · ≥ 4.9

Atherogenic Index of Plasma (Dobiasova 2011)

• < 0.11 low cardiovascular risk · 0.11–0.21 intermediate · > 0.21 high risk

Frequently asked questions

What is a good cholesterol ratio range?

For Total Cholesterol / HDL — the most-cited single ratio — under 3.5 is optimal, 3.5–5.0 is the AHA-acceptable range, and over 5.0 is high. Women have slightly tighter targets at the high end. The 2018 AHA/ACC guideline emphasizes that the ratio is not as informative on its own as non-HDL cholesterol in the context of overall ASCVD risk — which is why this calculator returns both, plus three other metrics.

Is cholesterol ratio more important than LDL?

Not exactly — LDL is still the AHA's primary treatment target for most adults. Ratios are useful complementary signals, especially when LDL-only values look normal but the underlying particle picture (small-dense LDL, high triglycerides, low HDL) is concerning. The Atherogenic Index of Plasma and the TG/HDL ratio capture that hidden risk in adults who have a "normal" LDL but elevated cardiovascular risk on more sensitive imaging or particle-count testing. Knowing all five metrics gives you and your clinician a richer picture than any single number.

What is a good ratio of HDL to triglycerides?

It's the inverse — TG-to-HDL — that's typically calculated. In mg/dL units, under 2.0 is considered ideal, 2.0–4.0 borderline, and over 4.0 high. In mmol/L, under 0.87 is ideal. TG/HDL is one of the strongest single surrogate markers for insulin resistance and small-dense LDL — moving it requires lowering triglycerides (carbohydrate quality, weight management, omega-3) and raising HDL (aerobic activity, smoking cessation, weight loss).

How do I calculate cholesterol ratios in mmol/L?

Switch the unit toggle at the top of the calculator from mg/dL to mmol/L. Every input field, every result chip, and every reference band converts on the fly. Conversion factors are 38.67 mg/dL per mmol/L for total, LDL, and HDL cholesterol; 88.57 mg/dL per mmol/L for triglycerides. The tool handles those internally so you don't have to.

Can I embed this tool on my own site?

Yes — copy the embed snippet at the bottom of this page. The embedded version is a stripped-down variant designed for primary care educators, registered dietitians, lipid clinic patient-education materials, and personal blogs. Required attribution is built in. There's no fee, no signup, no analytics attached.

Related tools

• Lean Body Mass Calculator — body composition affects insulin resistance, which drives the TG/HDL and AIP ratios.
• Steps to Miles Calculator — daily aerobic activity is the single best lever for raising HDL.
• Pulse Oximeter Reading Chart — useful for adults with cardiovascular comorbidities.
• Wong-Baker FACES® Pain Scale — useful when statin-associated myalgia shows up.
• Browse all free tools by Dr. Taylor →

Dr. Taylor's recommendations alongside this calculator

Three categories cover most of what's worth supplementing alongside a lipid-panel review. Each links to the full review with current top picks, prices, and pros/cons:

• Best CoQ10 Supplements — frequently co-supplemented in adults on statin therapy. Statins inhibit the same enzyme pathway (HMG-CoA reductase) that synthesizes endogenous CoQ10, so depletion is real even if the symptomatic-myalgia evidence is mixed (Banach 2015 meta-analysis). Worth discussing with your clinician.
• Best Fiber Supplements — soluble fiber (psyllium especially) lowers LDL by 5–10% in adults with elevated cholesterol per multiple AHA-cited trials. The cheapest, lowest-side-effect lever in the entire lipid-management toolkit.
• Best Blood Pressure Monitors — lipids and blood pressure travel together as ASCVD risk factors. If you're tracking lipids over time, you should be tracking BP at home too. Pair with the BP-at-home guide for technique.

Sources & methodology

• Castelli WP. Lipoproteins and cardiovascular disease. Am J Med 1984; 76(2A):4–12 — TC/HDL ratio framework.
• Castelli WP, Anderson K, Wilson PWF, Levy D. Lipids and risk of coronary heart disease: The Framingham Study. Ann Epidemiol 1992; 2(1–2):23–28 — Castelli risk indices.
• Grundy SM, Stone NJ, Bailey AL, et al. 2018 AHA/ACC/AACVPR/AAPA/ABC/ACPM/ADA/AGS/APhA/ASPC/NLA/PCNA Guideline on the Management of Blood Cholesterol. Circulation 2019; 139:e1082–e1143 — non-HDL targets, ASCVD risk thresholds.
• Dobiasova M, Frohlich J. The plasma parameter log (TG/HDL-C) as an atherogenic index. Clin Biochem 2001; 34(7):583–588 — AIP formula and bands.
• Murguia-Romero M, Jimenez-Flores JR, Sigrist-Flores SC, et al. Plasma triglyceride/HDL-cholesterol ratio, insulin resistance, and cardiometabolic risk in young adults. J Lipid Res 2013; 54(10):2795–2799 — TG/HDL bands.
• Friedewald WT, Levy RI, Fredrickson DS. Estimation of the concentration of low-density lipoprotein cholesterol in plasma, without use of the preparative ultracentrifuge. Clin Chem 1972; 18(6):499–502 — LDL backfill formula.

This tool is reviewed every 6 months for citation currency, with the next major guideline check pending the AHA/ACC 2027 update. About Dr. Taylor · Last reviewed May 6, 2026.

Embed this tool on your site

Free for primary care educators, registered dietitians, lipid clinic patient-education materials, nursing schools, and personal health blogs. Required attribution is included in the snippet. No fee, no signup, no analytics attached to the embed.

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