Cholesterol Ratio Calculator

What is a cholesterol ratio?

Cholesterol travels in the blood inside lipoproteins. LDL carries cholesterol that can build up in artery walls; HDL helps carry cholesterol away to the liver. A ratio combines the 'harmful' and 'protective' parts into one number, which is why it predicts heart and circulation problems better than total cholesterol alone. Two people can both have a total cholesterol of 200 mg/dL, but if one has an HDL of 70 and the other 35, their ratios – 2.9 and 5.7 – tell very different stories.

Total cholesterol to HDL ratio (TC/HDL)

The most widely reported ratio, used in the UK QRISK3 cardiovascular risk score and printed on many UK lab reports. Lower is better. Most doctors want it below 5:1, and below 3.5:1 is considered very good.

LDL/HDL ratio

Compares 'bad' with 'good' cholesterol directly. It is used less often in current guidelines, which focus on LDL and non-HDL values, but many people still see it on reports. Lower is better; values below about 2–2.5 are often described as favourable.

Triglyceride/HDL ratio

A high triglyceride level with a low HDL is a pattern linked with insulin resistance and metabolic syndrome. In mg/dL, research studies often treat a TG/HDL ratio below about 2 as favourable and above about 3–4 as a warning sign, but it is not a diagnostic test and thresholds differ between populations. Because the units differ, a TG/HDL ratio in mmol/L is not the same number as in mg/dL – the calculator labels which one you are seeing.

Non-HDL cholesterol

Non-HDL cholesterol (total − HDL) captures all the cholesterol in potentially harmful particles, including LDL and remnants. UK guidance gives a healthy non-HDL level of below 4 mmol/L, and many lipid guidelines now use non-HDL alongside or instead of LDL.

Cholesterol ratio chart

A ratio is one input to a cardiovascular risk assessment, alongside age, sex, blood pressure, smoking, diabetes, family history and other factors. A 'good' ratio does not rule out risk if LDL is very high or you have other risk factors, and a borderline ratio may matter little in a young non-smoker.

Reference levels: US and UK

Targets are lower for people who already have heart disease, diabetes or other high-risk conditions, so always use the targets your clinician gives you.

How to calculate your cholesterol ratio from a blood test

1. Find total cholesterol and HDL on your lipid panel, and note the unit (mg/dL in the US; mmol/L in the UK, Europe, Canada and Australia).
2. Divide total cholesterol by HDL. US example: 200 ÷ 50 = 4.0. UK example: 5.2 ÷ 1.3 = 4.0.
3. For LDL/HDL, divide LDL by HDL; for TG/HDL, divide triglycerides by HDL.
4. For non-HDL, subtract HDL from total cholesterol: 200 − 50 = 150 mg/dL, or 5.2 − 1.3 = 3.9 mmol/L.

Converting mg/dL and mmol/L

For total, LDL, HDL and non-HDL cholesterol, mg/dL = mmol/L × 38.67 (so 5.0 mmol/L ≈ 193 mg/dL). For triglycerides, mg/dL = mmol/L × 88.57. The TC/HDL and LDL/HDL ratios are the same in either unit because both numbers use the same conversion factor; the TG/HDL ratio is not.

If your LDL is missing

Labs often calculate LDL with the Friedewald equation: LDL = total − HDL − triglycerides ÷ 5 (in mg/dL). With TC 200, HDL 50 and TG 150, LDL ≈ 200 − 50 − 30 = 120 mg/dL. The equation is unreliable when triglycerides are high (400 mg/dL or more) and less accurate at very low LDL, which is why many labs now use newer methods (such as the Martin-Hopkins or Sampson equations) or measure LDL directly.

What changes your cholesterol ratio?

• Diet: replacing saturated fat with unsaturated fat lowers LDL; soluble fibre (oats, beans) helps too.
• Physical activity raises HDL modestly and lowers triglycerides.
• Weight loss and cutting alcohol and refined carbohydrates lower triglycerides.
• Stopping smoking raises HDL.
• Medicines such as statins lower LDL and non-HDL substantially; your doctor will decide whether you need them based on overall risk.
• Some conditions – underactive thyroid, kidney or liver disease, poorly controlled diabetes – and some medicines affect lipids.

Fasting or non-fasting?

Many labs now accept non-fasting samples for routine cholesterol checks, because total and HDL cholesterol change little after eating. Triglycerides rise after meals, so a fasting test may be requested if they are high or if your clinician needs a precise LDL estimate.

Example results explained

• Alex: TC 220, HDL 65, LDL 130, TG 125 mg/dL. TC/HDL = 3.4 (very good), but LDL is borderline. Overall risk depends on other factors such as blood pressure and smoking.
• Sam: TC 190, HDL 35, LDL 120, TG 175 mg/dL. Total cholesterol looks fine, but TC/HDL = 5.4 and TG/HDL = 5.0 – a pattern worth discussing, often improved by activity, weight loss and less refined carbohydrate and alcohol.
• Priya (UK): TC 6.1, HDL 1.6 mmol/L. TC/HDL = 3.8 and non-HDL = 4.5 mmol/L, slightly above the NHS healthy level of 4.

How ratios are used in risk calculators

Doctors rarely act on one cholesterol number alone. In the UK, the QRISK3 score uses the total cholesterol to HDL ratio, together with age, sex, ethnicity, blood pressure, smoking, diabetes, family history and other conditions, to estimate 10-year risk of heart attack or stroke. In the US, the ACC/AHA Pooled Cohort Equations use total and HDL cholesterol separately. Treatment decisions – including whether to start a statin – are based on that overall risk and on LDL or non-HDL levels.

Very high LDL and familial hypercholesterolaemia

An LDL of 190 mg/dL (about 4.9 mmol/L) or higher in an adult, or a strong family history of early heart disease, can point to familial hypercholesterolaemia (FH), an inherited condition thought to affect roughly 1 in 250 people. FH needs medical assessment because it raises risk from a young age, and close relatives may also need testing. A good ratio does not rule FH out.

Children and teenagers

Reference levels are different for young people. The US NHLBI expert panel describes acceptable levels for children and teenagers as total cholesterol below 170 mg/dL, LDL below 110 mg/dL, non-HDL below 120 mg/dL and HDL above 45 mg/dL. Talk to a paediatrician about testing, especially if there is a family history of high cholesterol.

How often should you check your cholesterol?

In the US, the CDC suggests most healthy adults have cholesterol checked every four to six years, more often if they have heart disease, diabetes or a family history. In England, the NHS Health Check for adults aged 40 to 74 includes a cholesterol test every five years. People on cholesterol-lowering treatment are usually tested more often to check the effect.

Questions to ask your doctor

• What is my estimated 10-year cardiovascular risk, and what score was it based on?
• Which target should I aim for – LDL, non-HDL or ratio – and what value?
• Would lifestyle changes alone be enough, or do you recommend medication?
• When should I repeat the test, and should it be fasting?
• Should my family be tested for inherited high cholesterol?

Reading your lab report

Lab reports usually show each result with a reference range and flag values as high (H) or low (L). Reference ranges describe typical values in the population, not your personal target, so a result inside the range can still be higher than your doctor wants if your overall risk is high. Check the units – mmol/L and mg/dL numbers look very different – and whether LDL was measured directly or calculated.

Other lipid tests you might see

Some reports include apolipoprotein B (ApoB), which counts the number of potentially harmful particles, and lipoprotein(a) [Lp(a)], an inherited particle linked to higher risk that many guidelines suggest measuring at least once in adulthood. These are not part of the ratios here, but your clinician may use them to refine risk.

Sources

1. NHS – Cholesterol levels — nhs.uk/conditions/high-cholesterol/cholesterol-levels
2. NHLBI – ATP III cholesterol categories (Third Report of the NCEP Expert Panel) — nhlbi.nih.gov
3. UMass Memorial Health Library (WebMD Ignite) – Lipid panel with total cholesterol:HDL ratio — ummhealth.org
4. Friedewald W.T. et al. (1972) Clin Chem 18:499–502 — doi.org/10.1093/clinchem/18.6.499