About the Cholesterol Ratio Calculator
A lipid panel comes back as a handful of numbers — total cholesterol, HDL, LDL, triglycerides — and the total-to-HDL ratio is the most popular way of boiling them down to one.
It earns that popularity. It weighs the cholesterol that tends to build up in artery walls against the HDL that tends to carry it away, and it predicts heart disease better than total cholesterol on its own.
But a ratio has a blind spot: it has no size. Two very different panels can share the same ratio. So this cholesterol ratio calculator reports the ratio together with non-HDL cholesterol, estimates LDL where the estimate is valid, and explains the one common ratio that changes when you switch units.
How to Use the Cholesterol Ratio Calculator
Choose your units — mg/dL (US) or mmol/L (UK, Europe, Canada, Australia) — and your sex, which sets the threshold for low HDL.
Enter total cholesterol and HDL. These two are all the ratio needs.
LDL and triglycerides are optional. If you enter triglycerides but not LDL, LDL is estimated for you.
How the Numbers Are Worked Out
Total-to-HDL ratio = total ÷ HDL
Non-HDL cholesterol = total − HDL
LDL-to-HDL ratio = LDL ÷ HDL
Triglyceride-to-HDL = triglycerides ÷ HDL
Friedewald LDL (mg/dL) = total − HDL − triglycerides ÷ 5
Friedewald LDL (mmol/L) = total − HDL − triglycerides ÷ 2.2Step-by-Step Example
Total 200 mg/dL, HDL 50, triglycerides 150, no LDL given.
Ratio: 200 ÷ 50 = 4.0 (under 5, above 3.5)
Non-HDL: 200 − 50 = 150 mg/dL (above 130)
LDL: 200 − 50 − 150 ÷ 5 = 120 mg/dL
LDL ÷ HDL: 120 ÷ 50 = 2.4
TG ÷ HDL: 150 ÷ 50 = 3.0 (in mg/dL)The ratio passes the usual target, but non-HDL is above the desirable level. That combination is exactly what the ratio alone would hide.
What the Ratio Hides
Consider two panels:
Panel A: total 200, HDL 50 → ratio 4.0, non-HDL 150
Panel B: total 280, HDL 70 → ratio 4.0, non-HDL 210Same ratio. But panel B carries 60 mg/dL more of the cholesterol that can deposit in arteries, and a good HDL does not cancel that out.
Non-HDL cholesterol is total minus HDL: LDL plus the remnant particles that also contribute to plaque. It works on a non-fasting sample, and many guidelines now treat it as at least as useful as LDL. Desirable is under 130 mg/dL, about 3.4 mmol/L; UK guidance uses 4 mmol/L as the level that prompts a closer look.
Ratio Targets
| Total-to-HDL ratio | Reading |
|---|---|
| 3.5 or below | Ideal |
| Under 5 | The usual target |
| 5 or above | Linked with higher heart disease risk |
Low HDL is usually taken as under 40 mg/dL (1.0 mmol/L) for men and under 50 mg/dL (1.3 mmol/L) for women. Low HDL pushes the ratio up by itself, and it responds to exercise, stopping smoking and losing excess weight.
Which Ratios Change With Units
Total, HDL and LDL all convert between units with the same factor — about 38.67 mg/dL per mmol/L, which comes from cholesterol's molar mass. Divide one by another and the factor cancels. The total-to-HDL ratio is identical in either unit.
Triglycerides convert with a different factor, about 88.57, because a triglyceride molecule is more than twice as heavy. So:
TG/HDL in mg/dL = TG/HDL in mmol/L × 88.57 ÷ 38.67
= TG/HDL in mmol/L × 2.29A published triglyceride-to-HDL cut-off of 3 is almost always in mg/dL. In mmol/L the equivalent is about 1.3. Comparing the wrong pair makes a normal result look alarming, or the reverse.
The same arithmetic explains Friedewald's two divisors. The 2.2 used in mmol/L is simply the mg/dL divisor of 5 converted: 5 × 38.67 ÷ 88.57 ≈ 2.18.
When the LDL Estimate Fails
Friedewald's estimate assumes a fixed relationship between triglycerides and the cholesterol they carry. That assumption breaks when triglycerides reach 400 mg/dL (about 4.5 mmol/L), and the calculator declines to estimate LDL above that. A directly measured LDL is needed instead — and triglycerides that high deserve attention in their own right.
Getting a Result You Can Compare
Cholesterol results move between tests for reasons that have nothing to do with your arteries, so a little care makes them easier to compare over time.
Fasting mostly matters for triglycerides. Total, HDL and non-HDL change very little after a meal, which is why many labs no longer insist on fasting. If your triglycerides come back high on a non-fasting sample, a fasting repeat is the usual next step, and it also makes a calculated LDL more trustworthy.
Illness, recent surgery and pregnancy can shift results for weeks. A test taken during any of them is a poor baseline.
Use the same lab where you can. Methods differ slightly between labs, and small changes between them may be measurement rather than biology.
Look at the trend. A single panel is a snapshot; two or three over a year or two show the direction of travel far better.
Understanding Your Result
Total-to-HDL ratio is the headline figure.
What it means places it against the ideal and the usual target.
Non-HDL cholesterol shows the size the ratio leaves out.
LDL cholesterol is your entered figure or the Friedewald estimate, with the LDL-to-HDL ratio.
Triglyceride-to-HDL ratio is shown in mg/dL terms, with the mmol/L figure beside it where relevant.
Worth knowing flags low HDL, a flattering ratio, or very high triglycerides.
When Should You Use This Calculator?
When a lab report gives the numbers but not the ratio.
When comparing results across countries or labs that use different units.
To see whether a good ratio is hiding a raised non-HDL.
Not to decide on treatment. That depends on overall cardiovascular risk.
Common Mistakes
Judging on the ratio alone. Check non-HDL too.
Comparing a TG/HDL figure against a cut-off in the other unit. They differ by 2.29 times.
Trusting a calculated LDL with very high triglycerides. It is not valid there.
Assuming high HDL cancels high LDL. It does not.
Reading one result as a trend. Cholesterol varies between tests.
Cholesterol is one part of heart risk alongside blood pressure, smoking, diabetes, age and family history. Talk to a doctor about what your numbers mean for you. Nothing here is medical advice.