Cholesterol mg/dL to mmol/L — With the Right Factor

American labs report cholesterol in mg/dL. Most of the rest of the world, and a good share of the research literature, reports it in mmol/L. The bridge is a single number: divide mg/dL by 38.67. A total cholesterol of 200 mg/dL is 5.17 mmol/L.

One lab panel, three different factors

This is the mistake worth reading the page for. A standard lipid panel prints four numbers, and they do not all convert the same way — because the factor comes from the molar mass of whatever is being counted, and they are different molecules.

Line on the report	Divide mg/dL by
Total cholesterol	38.67
LDL cholesterol	38.67
HDL cholesterol	38.67
Triglycerides	88.57

Cholesterol weighs about 386.7 grams per mole; a typical triglyceride is more than twice as heavy, around 885 grams per mole. Applying 38.67 to a triglyceride reading of 150 mg/dL gives 3.88 mmol/L when the answer is 1.69 — more than double, and far enough to move a borderline result into a range it does not belong in.

The NIDDK reference tables in Diabetes in America state the same relationships as multipliers: cholesterol × 0.0259 and triglycerides × 0.0113. Those are the reciprocals of 38.6 and 88.5, and they agree with the divisors above to within rounding.

Your cholesterol in both units

mg/dL	mmol/L
130 mg/dL	3.36 mmol/L
150 mg/dL	3.88 mmol/L
170 mg/dL	4.40 mmol/L
190 mg/dL	4.91 mmol/L
200 mg/dL	5.17 mmol/L
240 mg/dL	6.21 mmol/L
280 mg/dL	7.24 mmol/L
300 mg/dL	7.76 mmol/L

Two mental anchors: 200 mg/dL is a little over 5 mmol/L, and every 40 mg/dL is roughly 1 mmol/L.

Why two units exist at all

mg/dL counts mass — how many milligrams of cholesterol sit in each tenth of a litre of blood. mmol/L counts particles — how many millimoles of the molecule per litre. Both describe the same blood; they answer different questions about it.

The particle count is arguably the more meaningful of the two, which is why the international system settled on it, and it is why the conversion needs a molar mass at all. The mass unit survives in the US because every reference range, guideline and decades-old chart is written in it, and changing the unit would mean rewriting all of them at once.

What the converted number does and does not tell you

A number in mmol/L is still just a number. Whether a given cholesterol level warrants action depends on the rest of your cardiovascular risk — age, blood pressure, smoking, diabetes, family history — not on the value alone, and the thresholds differ between guidelines as well as between units. Converting the unit does not convert the interpretation, and it does not make a foreign guideline’s cutoff apply to you.

For the other line on the same report that everyone converts, see blood sugar mg/dL to mmol/L, which uses a third factor again. And for the unit that blood pressure is reported in — the one number on a checkup that has no conversion at all — see blood pressure units.

This content is informational, converts units only, and does not replace a clinician’s reading of your lipid panel.