Cholesterol Converter & Ratio Calculator
Convert cholesterol and triglycerides between mg/dL and mmol/L, and from a lipid panel work out non-HDL cholesterol, the total-to-HDL ratio and LDL by the Friedewald and the Sampson (NIH) equations, each compared with the MedlinePlus healthy levels.
How to Use
- Choose Lipid panel to work from a test result, or Convert one value to change a single number between mg/dL and mmol/L.
- For a panel, pick the unit your report uses and type total cholesterol, HDL cholesterol and triglycerides.
- Pick sex and age group: the MedlinePlus healthy levels differ for HDL in women and men, and for everyone 19 or younger.
- Read LDL by the Sampson (NIH) equation and by Friedewald, non-HDL cholesterol and the total-to-HDL ratio; the chart shows each number against its healthy level.
- Show Work lists every step, including the conversion to mg/dL that both LDL equations need.
Worked Example
A routine panel in mg/dL. Total 200, HDL 50, triglycerides 150. Non-HDL is 200 − 50 = 150 mg/dL and the ratio 200 ÷ 50 = 4.00. Friedewald: 200 − 50 − 150 ÷ 5 = 120 mg/dL. Sampson: the VLDL term is 150 ÷ 8.56 + 150 × 150 ÷ 2140 − 150² ÷ 16100 = 26.6, so LDL = 200 ÷ 0.948 − 50 ÷ 0.971 − 26.6 − 9.44 = 123.4 mg/dL, above the MedlinePlus adult healthy level of under 100.
The same kind of panel in mmol/L. Total 5.2, HDL 1.3 and triglycerides 1.7 mmol/L are first turned into mg/dL, because both LDL equations were fitted in mg/dL: 5.2 × 38.67 = 201.1, 1.3 × 38.67 = 50.3 and 1.7 × 88.55 = 150.5. Sampson then gives 124.1 mg/dL, which is 3.21 mmol/L; Friedewald gives 120.7 mg/dL, or 3.12 mmol/L.
The common mistake: converting triglycerides with the cholesterol factor. 1.7 mmol/L × 38.67 = 66 mg/dL looks comfortably healthy, but triglycerides are a heavier molecule: 1.7 × 88.55 = 151 mg/dL, just into the MedlinePlus borderline-high band of 150–199.
Show Work
Formulas
From Friedewald to the NIH Equation
Measuring LDL directly once meant spinning plasma in an ultracentrifuge. In 1972 William Friedewald, Robert Levy and Donald Fredrickson published a shortcut in Clinical Chemistry: LDL is total cholesterol minus HDL minus the cholesterol carried in VLDL, and VLDL cholesterol could be estimated as triglycerides ÷ 5. Labs have used it on the standard lipid panel ever since.
The weak point is that fixed 5. The ratio of triglyceride to cholesterol in VLDL varies, so the estimate drifts at low LDL and high triglycerides, and labs stop reporting it at 400 mg/dL. In 2020 Maureen Sampson and colleagues at the National Institutes of Health fitted a new equation to 18,715 β-quantification results from 8,656 patients seen at the NIH Clinical Center between 1976 and 1999. Using triglycerides and non-HDL cholesterol, it estimates VLDL with a TG × non-HDL term and a TG² correction, and in their tests it was more accurate than Friedewald, with 35% fewer misclassifications between 400 and 800 mg/dL triglycerides.
The unit factors here are worked out from molar masses (cholesterol 386.66 g/mol, triolein 885.45 g/mol) and agree with the rounded SI factors JAMA prints, × 0.0259 and × 0.0113, to three figures.
About This Tool
This calculator takes a lipid panel in mg/dL or mmol/L and gives non-HDL cholesterol, the total-to-HDL ratio and two LDL estimates, Sampson (NIH) and Friedewald, with the limits of each applied. It also converts a single value either way. Every number is compared with the healthy levels MedlinePlus (the US National Library of Medicine) gives for adults and for people 19 or younger, and with its four adult triglyceride bands.
Healthy levels are a general guide; the numbers that suit you depend on age, blood pressure, diabetes, smoking and family history, and a doctor weighs them together. For general information only — not medical advice. Talk to a doctor or other qualified professional about your own health.
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Frequently Asked Questions
How do I convert cholesterol from mg/dL to mmol/L?
Divide by 38.67, the molar mass of cholesterol (386.66 g/mol) over 10. So 200 mg/dL is 5.17 mmol/L, 130 mg/dL is 3.36 and 100 mg/dL is 2.59. The same factor works for total, LDL, HDL and non-HDL cholesterol, because each is measured as cholesterol.
Why do triglycerides use a different factor?
Triglycerides are a different molecule. Labs count them as triolein (C₅₇H₁₀₄O₆, 885.45 g/mol), so you divide mg/dL by 88.55: 150 mg/dL is 1.69 mmol/L and 500 mg/dL is 5.65 mmol/L. Using the cholesterol factor instead turns 1.7 mmol/L into 66 mg/dL rather than the correct 151.
What is the difference between the Friedewald and Sampson LDL equations?
Friedewald (1972) estimates LDL as total − HDL − triglycerides ÷ 5, which loses accuracy at high triglycerides and is not used at 400 mg/dL or more. The Sampson (NIH) equation from 2020 adds an interaction term and works up to 800 mg/dL. For 240, 35 and 500 mg/dL, Friedewald is not valid, while Sampson gives 116.9 mg/dL.
What are healthy cholesterol levels?
MedlinePlus lists, for adults 20 and older: total under 200 mg/dL, LDL under 100, non-HDL under 130, and HDL of 60 or more as best (under 40 is low for men, under 50 for women). For people 19 or younger: total under 170, LDL under 110, non-HDL under 120, HDL over 45. Adult triglycerides are healthy under 150 mg/dL.
How is the cholesterol ratio worked out?
Divide total cholesterol by HDL cholesterol. A total of 200 mg/dL with HDL of 50 gives 4.00, and the ratio is the same in mmol/L (5.17 ÷ 1.29) because both numbers use the same factor. A lower ratio means a larger share of the total is HDL.
How do I use the Cholesterol Converter & Ratio Calculator?
Just type your numbers. The answer shows up right away — there is no button to press. Change anything and it updates by itself.
Is it free? Does it work without internet?
Yes to both. It is free with no sign-up, and once the page has loaded it keeps working even with no internet.
Where does my data go?
Nowhere — every calculation runs on your own device. Nothing you enter is uploaded, logged, or stored.
Common Use Cases
Reading a lab report
A report shows total 200, HDL 50 and triglycerides 150 mg/dL: LDL 123.4 by the Sampson equation, 120 by Friedewald, non-HDL 150 and a ratio of 4.00.
Results in mmol/L
Total 5.2, HDL 1.3 and triglycerides 1.7 mmol/L become 201, 50 and 151 mg/dL, giving LDL 3.21 mmol/L (Sampson) and 3.12 (Friedewald).
High triglycerides
With triglycerides of 500 mg/dL, Friedewald is not valid; the Sampson equation still gives an LDL of 116.9 mg/dL for a total of 240 and HDL of 35.
Low LDL on treatment
Total 130, HDL 45 and triglycerides 180 mg/dL give LDL 55.2 by Sampson and 49 by Friedewald, a 6 mg/dL difference that matters at low targets.
Comparing with an overseas guideline
An LDL of 3.0 mmol/L is 116 mg/dL, above the 100 mg/dL MedlinePlus healthy level for adults.
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