How to use the cholesterol ratio calculator
- Pick mg/dL (US reports) or mmol/L (Canada, the UK, Australia, most of Europe). Typed numbers convert when you switch.
- Enter Total cholesterol and HDL. Both are required.
- Add LDL if your report lists it. If not, leave it blank and enter Triglycerides to estimate it.
- Pick Male or Female, which only sets the low-HDL cut-off.
How the ratios are calculated
Total cholesterol to HDL is total cholesterol divided by HDL, LDL to HDL is LDL divided by HDL, and non-HDL cholesterol is total minus HDL. Ratios have no units, so mg/dL and mmol/L agree. Each ratio is rounded to one decimal, like a lab report, before it gets a label.
For total cholesterol to HDL, 3.5 or lower is optimal and under 5 is the usual target, per Mayo Clinic. For LDL to HDL, under 2.5 is favorable and over 3.5 is above range, a common rule of thumb: no major guideline sets official cut-offs, and sources differ by about a point.
With LDL blank, the tool uses the Friedewald equation: total cholesterol minus HDL minus triglycerides ÷ 5 (mg/dL), valid below 400 mg/dL of triglycerides per the CDC's NHANES documentation. The bands beside each reading in the table come from the NHLBI ATP III report and MedlinePlus.
Worked example
With the starting numbers (total 200, HDL 50, LDL 120, triglycerides 150, all mg/dL), total cholesterol to HDL is 200 ÷ 50 = 4.0 (Within target), LDL to HDL is 120 ÷ 50 = 2.4 (Favorable), and non-HDL cholesterol is 200 − 50 = 150 mg/dL. The table reads total cholesterol Borderline high, LDL Near optimal, HDL Acceptable for a man and triglycerides Borderline high. Estimating LDL gives 200 − 50 − 150 ÷ 5 = 120, matching your entry.
Limits and edge cases
A ratio hides its parts: total 300 with HDL 75 also gives 4.0. The 2026 ACC/AHA dyslipidemia guideline sets goals as LDL-C and non-HDL-C values by risk level (LDL-C under 100 and non-HDL-C under 130 at borderline or intermediate risk), so use this page for screening, not treatment decisions. An LDL of 190 or higher, or triglycerides of 500 or higher, deserve a doctor's attention whatever the ratio. Total cholesterol must be 50 to 1,000 mg/dL (1.3 to 25.9 mmol/L), and ranges are for adults. In mmol/L the bands use the rounded cut-offs printed beside each reading (5.2, 2.6, 3.4, 4.9), so 5.17 mmol/L, which is 200 mg/dL, reads Desirable because it is under 5.2. See also the blood pressure analyzer, waist-to-hip ratio calculator and BMI calculator.
Frequently asked questions
What is a good cholesterol ratio?
A total cholesterol to HDL ratio of 3.5 or lower is considered optimal, and Mayo Clinic advises staying below 5. Your LDL, non-HDL cholesterol and overall risk matter more than the ratio alone.
Is the cholesterol ratio or non-HDL cholesterol more useful?
Many clinicians prefer non-HDL cholesterol (total minus HDL). Mayo Clinic says it may be more useful than the ratio, and the 2026 ACC/AHA guideline sets goals as LDL-C and non-HDL-C, not ratios. The ratio still screens well: in the Framingham Offspring Study, heart disease risk rose two- to threefold from the lowest to the highest third of the ratio.
Can I estimate LDL instead of typing it in?
Yes. Leave LDL blank and enter triglycerides: the calculator subtracts HDL and one fifth of the triglycerides from total cholesterol. It is not valid at 400 mg/dL (4.5 mmol/L) of triglycerides or more, so use your lab's LDL then.
Does a high ratio mean I have heart disease?
No. A ratio is a risk marker, not a diagnosis. Doctors estimate 10-year risk with tools such as the PREVENT equations, which also weigh age, blood pressure, diabetes and smoking.
Sources: Mayo Clinic; NHLBI ATP III; MedlinePlus (cholesterol, triglycerides); CDC NHANES; 2026 ACC/AHA guideline; Nam et al., Am J Cardiol 2006.