mg/dL to mmol/L Converter

mg/dL to mmol/L: the short answer

To convert mg/dL to mmol/L, divide by the substance's molar mass and multiply by 10:

mmol/L = mg/dL × 10 ÷ molar mass (g/mol)

To go back: mg/dL = mmol/L × molar mass ÷ 10

Because every substance has a different molar mass, every substance has a different factor. The most commonly needed ones are:

• Glucose: divide mg/dL by 18 (more precisely 18.016) – 100 mg/dL = 5.6 mmol/L
• Cholesterol (total, LDL, HDL): divide by 38.67 – 200 mg/dL = 5.17 mmol/L
• Triglycerides: divide by 88.57 – 150 mg/dL = 1.69 mmol/L
• Calcium: divide by 4.008 – 10 mg/dL = 2.50 mmol/L
• Magnesium: divide by 2.431 – 2.0 mg/dL = 0.82 mmol/L
• Phosphate: divide by 3.097 – 3.5 mg/dL = 1.13 mmol/L
• Urea from BUN: multiply BUN by 0.357 – 14 mg/dL BUN = 5.0 mmol/L urea

The converter above includes every mg/dL test on AskDr. Pick the substance, enter a value and read the answer in the other unit.

Where the formula comes from

A mole is a fixed number of molecules (about 6.022 × 10²³). The molar mass is the mass of one mole of a substance in grams. Glucose (C₆H₁₂O₆) has a molar mass of 180.16 g/mol, so one millimole of glucose weighs 180.16 mg.

A concentration of 1 mg/dL means 1 mg in 100 mL, or 10 mg per litre. To find how many millimoles that is, divide 10 mg by the mass of one millimole:

10 mg/L ÷ 180.16 mg/mmol = 0.0555 mmol/L

So 1 mg/dL of glucose = 0.0555 mmol/L, and 1 mmol/L = 18.016 mg/dL. The same logic gives each factor in the table below.

Worked examples, step by step

Glucose, 162 mg/dL: 162 × 10 = 1,620; 1,620 ÷ 180.16 = 8.99 mmol/L – about 9.0.

LDL cholesterol, 116 mg/dL: 116 × 10 = 1,160; 1,160 ÷ 386.65 = 3.00 mmol/L – the European low-risk LDL goal.

Triglycerides, 500 mg/dL: 500 × 10 = 5,000; 5,000 ÷ 885.4 = 5.65 mmol/L – the threshold at which pancreatitis risk becomes a concern.

Calcium, 9.2 mg/dL: 9.2 × 10 = 92; 92 ÷ 40.08 = 2.30 mmol/L.

Magnesium, 1.5 mg/dL: 1.5 × 10 = 15; 15 ÷ 24.31 = 0.62 mmol/L – low.

Going backwards is equally simple. A glucose of 4.2 mmol/L × 180.16 ÷ 10 = 75.7 mg/dL, and a total cholesterol of 6.5 mmol/L × 386.65 ÷ 10 = 251 mg/dL.

Why molar units suit physiology

Molar units count molecules rather than weighing them, and the body works with molecules. Several practical advantages follow:

• Calculated osmolality becomes a simple sum in SI units: 2 × sodium + glucose + urea, with no conversion constants.
• Ratios between substances become meaningful. For example, the molar ratio of urea to creatinine reflects how the kidneys handle each molecule.
• Drug and hormone interactions depend on numbers of molecules binding to receptors, not on their weights.
• Teaching chemistry and physiology is easier when lab values use the same units as chemistry textbooks.

The main advantage of mass units is familiarity: generations of US clinicians learned thresholds such as 126 mg/dL for glucose and 200 mg/dL for cholesterol.

Conversion factors and molar masses

For substances reported in µmol/L, the factor is 1,000 times larger: creatinine (113.12 g/mol) converts from mg/dL to µmol/L by multiplying by 88.4, uric acid (168.11 g/mol) by 59.48 and bilirubin (584.66 g/mol) by 17.1.

Glucose: mg/dL to mmol/L

Glucose is by far the most common conversion, because meters, CGMs and lab reports use different units in different countries.

Quick mental conversion: divide mg/dL by 18 – or, as an approximation, divide by 20 and add 10%. For 180 mg/dL: 180 ÷ 20 = 9, plus 10% = 9.9, close to the exact 10.0. To go the other way, multiply mmol/L by 18 – or double it, multiply by 10 and subtract 10%: 7 mmol/L → 140 − 14 = 126 mg/dL.

For a complete glucose conversion chart, see our blood sugar converter. For long-term glucose, the A1C calculator and chart converts HbA1c to average glucose in both units.

Cholesterol: mg/dL to mmol/L

Quick mental conversion: divide mg/dL by 40 and add about 3%. For 200 mg/dL: 200 ÷ 40 = 5.0, plus 3% = 5.15, close to the exact 5.17.

The same factor applies to total cholesterol, LDL, HDL and non-HDL cholesterol, because all are measured as cholesterol.

Triglycerides: mg/dL to mmol/L

Quick mental conversion: divide by 88.6, or roughly by 90 and add about 1–2%. 150 ÷ 90 = 1.67, close to 1.69. Using the cholesterol factor (÷ 38.67) for triglycerides is a common mistake that produces results more than twice too high.

Electrolytes and minerals

Calcium

Calcium (40.08 g/mol) converts by dividing mg/dL by 4.008. The usual adult range of about 8.6–10.3 mg/dL equals 2.15–2.58 mmol/L. Because calcium carries two positive charges, 1 mmol/L = 2 mEq/L, which matters if your report uses mEq/L.

Magnesium

Magnesium (24.31 g/mol) converts by dividing mg/dL by 2.431. A typical range of 1.7–2.2 mg/dL equals about 0.70–0.91 mmol/L. Like calcium, it is divalent, so 1 mmol/L = 2 mEq/L.

Phosphate

US laboratories report "phosphorus" in mg/dL, meaning the phosphorus content of inorganic phosphate. Dividing by 3.097 (the atomic mass of phosphorus divided by 10) gives mmol/L. A typical adult range of 2.5–4.5 mg/dL equals 0.81–1.45 mmol/L.

Sodium, potassium and chloride

These are already reported in mmol/L (or the numerically identical mEq/L) almost everywhere, so they do not need converting.

Urea and BUN

US reports give BUN in mg/dL, which counts only the nitrogen in urea (two nitrogen atoms, 28 g/mol). Most other countries report urea in mmol/L. Because one urea molecule contains two nitrogen atoms, the conversion uses 28 rather than urea's full molar mass of 60:

• Urea (mmol/L) = BUN (mg/dL) × 0.357
• BUN (mg/dL) = urea (mmol/L) × 2.8

Some countries report urea in mg/dL (the whole molecule), in which case urea (mg/dL) = BUN × 2.14. Our BUN to urea converter covers all three.

Creatinine, uric acid and bilirubin: mg/dL to µmol/L

These three are also measured in mg/dL in the US but are reported in micromoles per litre elsewhere, because their concentrations are low. The factors are therefore 1,000 times larger than a mmol/L factor would be:

• Creatinine: × 88.4 – 1.0 mg/dL = 88 µmol/L; 1.5 mg/dL = 133 µmol/L. See our creatinine converter.
• Uric acid: × 59.48 – 6.0 mg/dL = 357 µmol/L, the usual treatment target in gout; 7.0 mg/dL = 416 µmol/L. See our uric acid converter.
• Bilirubin: × 17.1 – 1.2 mg/dL = 21 µmol/L; 3.0 mg/dL = 51 µmol/L, around the level at which jaundice becomes visible. See our bilirubin converter.

A frequent error is to report creatinine as "88 mmol/L" instead of "88 µmol/L". The number is right, but the unit is wrong by a factor of 1,000.

Glucose meters and CGMs

Glucose meters and continuous glucose monitors display either mg/dL or mmol/L, usually fixed by the country of sale. If you travel or buy a device abroad, check which unit it uses before relying on it: a reading of "8.0" is a normal post-meal glucose in mmol/L but would be impossibly low in mg/dL, while "140" makes sense only in mg/dL. CGM apps often let you change the display unit in settings, and your diabetes care team can help you set targets in the unit you use. Common CGM targets are 70–180 mg/dL (3.9–10.0 mmol/L) for time in range.

Pregnancy thresholds

In pregnancy, glucose targets are stricter, and conversion accuracy matters more. Common targets for people with diabetes in pregnancy are a fasting glucose below 95 mg/dL (5.3 mmol/L), one-hour post-meal below 140 mg/dL (7.8 mmol/L) and two-hour post-meal below 120 mg/dL (6.7 mmol/L). The UK uses similar targets of below 5.3, 7.8 and 6.4 mmol/L respectively. Note that 6.4 mmol/L is 115 mg/dL, not 120 – an example of how national guidelines sometimes choose round numbers in their own unit.

Converting a whole lipid panel: an example

A US lipid report shows total cholesterol 228 mg/dL, HDL 52 mg/dL, triglycerides 175 mg/dL and calculated LDL 141 mg/dL. Converting to mmol/L:

• Total cholesterol: 228 ÷ 38.67 = 5.90 mmol/L
• HDL: 52 ÷ 38.67 = 1.34 mmol/L
• Triglycerides: 175 ÷ 88.57 = 1.98 mmol/L
• LDL: 141 ÷ 38.67 = 3.65 mmol/L
• Non-HDL cholesterol: 228 − 52 = 176 mg/dL, and 176 ÷ 38.67 = 4.55 mmol/L. Subtracting the rounded SI values (5.90 − 1.34) gives 4.56 – a harmless rounding difference
• Total-to-HDL ratio: 228 ÷ 52 = 4.4 – identical in both units, because a ratio has no units

This is a useful check: ratios should be the same before and after conversion, and differences should convert with the same factor as the original values.

Converting in a spreadsheet

If you track results over time in a spreadsheet, a simple formula avoids repeated manual calculation. With a glucose value in mg/dL in cell A2, enter =A2/18.016 to get mmol/L, or =ROUND(A2/18.016,1) to round to one decimal place. For cholesterol, use =A2/38.67, and for triglycerides =A2/88.57. Keep a column with the unit next to each value, so that it is always clear which unit a number uses, and avoid mixing units in the same column.

Precision and rounding conventions

Laboratories round results to a level that reflects the precision of the test:

• Glucose: one decimal place in mmol/L (5.6), whole numbers in mg/dL (101)
• Cholesterol and triglycerides: one or two decimal places in mmol/L (5.17 or 5.2), whole numbers in mg/dL
• Calcium and phosphate: two decimal places in mmol/L (2.35), one in mg/dL (9.4)
• Creatinine: whole numbers in µmol/L (88), one or two decimal places in mg/dL (1.0 or 1.00)

Converting a rounded value and then rounding again can introduce small discrepancies. For example, 5.6 mmol/L converts to 100.9 mg/dL, while 5.55 mmol/L would convert to exactly 100. These differences are smaller than the normal day-to-day variation in the test itself and do not change clinical interpretation.

Common mistakes to avoid

1. Using the glucose factor for everything. Dividing cholesterol by 18 gives a value more than twice too high.
2. Confusing cholesterol and triglycerides. They use different factors even though both are "lipids" in mg/dL.
3. Mixing up BUN and urea. A urea of 7 mmol/L is a BUN of about 20 mg/dL, not 7.
4. Ignoring prefixes. Creatinine is in µmol/L, not mmol/L; 88 µmol/L is 0.088 mmol/L.
5. Rounding too early. Round the final answer, not intermediate steps.
6. Comparing with the wrong reference range. Convert the reference range too, or use the range on your report.

When to see a doctor

Converting a value helps you understand it but does not change what it means. Talk to your clinician if a converted result is outside the reference range on your report. For glucose, seek urgent help for readings below 54 mg/dL (3.0 mmol/L) that do not respond to treatment, or above about 300 mg/dL (16.7 mmol/L) with vomiting, drowsiness or rapid breathing.