Cholesterol Units Converter

Article — Cholesterol Units Converter

Cholesterol units converter: mg/dL and mmol/L

Cholesterol units convert between mg/dL and mmol/L using a factor of 38.67 for cholesterol fractions (total, HDL, LDL) and 88.57 for triglycerides. The factors come from molar mass. A US total cholesterol of 200 mg/dL is 5.17 mmol/L on a UK or European lab report; the underlying lipid level is identical.

The calculator above handles all four common lipid types. The US uses mg/dL; almost every other developed country uses mmol/L. Knowing the conversion lets you read a foreign lab report, compare guidelines across regions, and double-check a clinician's interpretation against the original numbers.

Cholesterol units explained

Cholesterol concentration in blood plasma can be expressed two ways. The US convention is mass per volume: milligrams per deciliter, mg/dL. The SI convention used almost everywhere else is moles per volume: millimoles per liter, mmol/L. Both describe the same physical quantity; only the unit of counting differs.

Mass-based units have one practical advantage. They are easier to compare directly to dietary intake, which is also measured in mass. Mole-based units have a scientific advantage: they reflect the actual number of molecules per liter, which is what matters for receptor binding and metabolism. SI was adopted as the international medical standard in the 1970s. Most countries followed; the United States did not for most clinical chemistry values, cholesterol included.

mg/dL to mmol/L conversion

Two factors are sufficient to convert any lipid value. Cholesterol fractions (total, HDL, LDL) divide by 38.67. Triglycerides divide by 88.57. The reverse direction multiplies by the same factor.

Mental shortcut. For cholesterol fractions, divide mg/dL by 39. A 200 mg/dL total cholesterol divided by 39 gives 5.13 mmol/L; the exact answer is 5.17. The shortcut error is under 1%. For triglycerides, divide by 89.

Why the cholesterol factor is 38.67

The factor is exactly: molar mass divided by 10. Cholesterol molar mass is 386.7 g/mol. mg/dL is milligrams per 0.1 liter; mmol/L is millimoles per liter. Converting mg to mmol divides by the molar mass; converting per dL to per L multiplies by 10. The combined operation is divide by 38.67.

The factor applies identically to every cholesterol fraction: total cholesterol, HDL, LDL, VLDL, non-HDL cholesterol, even Lp(a) (which reports in mg/dL on most assays). The reason is simple: all of these fractions are measured as mass of cholesterol per volume, and cholesterol is the same molecule regardless of which lipoprotein carries it.

Why the triglyceride factor is 88.57

Triglycerides are larger molecules than cholesterol. A typical triglyceride averages 885.7 g/mol, about 2.3 times the mass of a cholesterol molecule. The same logic gives a divisor of 88.57 instead of 38.67.

The exact triglyceride mass is an average. Triglycerides are not a single molecule but a class: a glycerol backbone with three fatty acid tails. The fatty acids vary, so the actual molar mass of a blood sample's triglyceride mix depends on diet. 885.7 is the figure used by clinical chemistry standards for assay calibration; the variation in real samples is small enough to ignore for clinical purposes.

Cholesterol reference ranges

The NIH ATP III reference ranges have been the global default since 2002. Total cholesterol under 200 mg/dL (5.17 mmol/L) is desirable. 200 to 239 mg/dL (5.17 to 6.18 mmol/L) is borderline high. 240+ mg/dL (6.21 mmol/L) is high.

Recent guidelines from the AHA and ESC place more emphasis on LDL and non-HDL cholesterol than total cholesterol alone, but the conversion math is unchanged. A "high LDL" of 190 mg/dL is the same 4.91 mmol/L number on a UK or German report. Only the unit label differs.

HDL and LDL cholesterol units

HDL and LDL use the same 38.67 factor as total cholesterol. The reference cutoffs are different because HDL is protective at high values and LDL is harmful at high values, but the unit conversion is identical.

• HDL low cutoff (men): 40 mg/dL = 1.03 mmol/L
• HDL low cutoff (women): 50 mg/dL = 1.29 mmol/L
• HDL protective level: 60 mg/dL = 1.55 mmol/L
• LDL optimal: < 100 mg/dL = < 2.59 mmol/L
• LDL borderline high: 130 mg/dL = 3.36 mmol/L
• LDL very high: 190 mg/dL = 4.91 mmol/L

Cholesterol units by country

The split is roughly geographic. North America, parts of Asia, Brazil, and Poland use mg/dL. The UK, EU, Canada (officially), Australia, and most of the developing world use mmol/L. Many countries appear in both columns because hospital systems have not all migrated to SI even where national standards say they should.

Patients with international medical records often see both units side by side. Many hospital systems print the SI value with the mg/dL equivalent in parentheses, especially when serving expatriate populations.

Common cholesterol unit mistakes

Applying the cholesterol factor to triglycerides. 88.57 not 38.67. Using 38.67 on triglycerides produces values 2.3 times too high — a normal 150 mg/dL appears as 3.88 mmol/L instead of the correct 1.69 mmol/L.

Confusing mg/dL with mg/L. Different by a factor of 10. mg/dL is the standard cholesterol unit. mg/L appears in some research papers and dietary intake tables. A 200 mg/dL value is 2000 mg/L, not 20.

Misreading reference ranges. A UK lab printing "5.2" looks like a low number to someone used to US mg/dL values, but it is the same lipid level as a US 201 mg/dL — borderline high, not safe. Always convert before judging.