The molar mass of cholesterol, C27H46O, is 386.664 g/mol. That single number is what connects a mass you can weigh to an amount of substance you can react: one mole is 386.664 g, and a gram of it is 1.557e+21 formula units. The calculator turns any weighed mass into that count, and reports the amount in moles, millimoles and the mass of a single formula unit alongside it.
The figure comes from the formula. Cholesterol is 27 × 12.011 (C) + 46 × 1.008 (H) + 15.999 (O), which is 386.664 g/mol, taking standard atomic weights, and every page here computes that sum rather than quoting it. Carbon makes up the largest share of the mass: 27 of the 74 atoms in a formula unit are carbon, and they account for 324.297 g of the 386.664 g, or 83.87% by mass. The derivation table below breaks the whole molecule down element by element.
The numbers a bench actually uses sit at the millimole scale. One millimole of cholesterol is 386.664 mg and one micromole is 386.664 µg, so a balance reading to a milligram places you within 2.586 µmol. A single formula unit weighs 6.4207e-22 g, which is why the count in the gauge runs into the sextillions for any mass you can see.
A membrane sterol and the reason lipid panels exist. Reported in mg/dL in the US and mmol/L elsewhere, with 200 mg/dL the familiar threshold. At 386.664 g/mol it is the heaviest of the 21 organic compounds covered here, and that ranking matters more than it looks: sucrose has a molar mass of 342.297 g/mol, so a gram of it contains 13% more formula units than a gram of cholesterol. Weigh by mass and you are not weighing equal amounts of substance.
Two practical things move the result. Purity below 100% means the weighed mass overstates how much compound you have — at 98% assay, 7.7333 g of every 386.664 g is not the compound — and any water picked up from the air does the same. Both are systematic, so they shift every solution made from that jar in the same direction.
The formula
m- The mass of cholesterol in grams
386.664- The molar mass of cholesterol in g/mol, derived from its formula
N- The number of formula units that mass contains
How it works, step by step
- Enter a mass of cholesterol in grams.
- It is divided by the molar mass, 386.664 g/mol, giving the amount in moles.
- That amount is multiplied by the Avogadro constant, 6.02214076 × 10²³ per mole, to give the number of formula units.
- The panel also reports the amount in moles and millimoles and the mass of one formula unit.
Worked examples
0.5 g of cholesterol as a molecule count
0.5 g divided by 386.664 g/mol is 0.00129311 mol, and multiplying by the Avogadro constant gives 7.787e+20 formula units of cholesterol. The same mass is 1.2931 mmol, which is the figure a reaction is actually planned in.
5 g of cholesterol as a molecule count
5 g divided by 386.664 g/mol is 0.0129311 mol, and multiplying by the Avogadro constant gives 7.787e+21 formula units of cholesterol. The same mass is 12.931 mmol, which is the figure a reaction is actually planned in.
50 g of cholesterol as a molecule count
50 g divided by 386.664 g/mol is 0.129311 mol, and multiplying by the Avogadro constant gives 7.787e+22 formula units of cholesterol. The same mass is 129.31 mmol, which is the figure a reaction is actually planned in.
How to read your score
Frequently asked questions
What is the molar mass of cholesterol (C27H46O)?
It is 386.664 g/mol. That is the sum of the standard atomic weights of every atom in the formula: 27 × 12.011 (C) + 46 × 1.008 (H) + 15.999 (O). One mole of cholesterol therefore weighs 386.664 g, and a gram of it is 2.5862 mmol.
What percentage of cholesterol is carbon?
83.87% by mass. Each formula unit contains 27 carbon atoms contributing 324.297 g of the 386.664 g total, so 100 g of cholesterol contains 83.87 g of carbon and a kilogram contains 838.7 g of it.
How many molecules are in one gram of cholesterol?
About 1.557e+21. One gram is 0.00258622 mol, and each mole contains 6.02214076 × 10²³ formula units by definition of the mole, so the count is that constant divided by 386.664.
How much does a single molecule of cholesterol weigh?
6.4207e-22 g, which is 386.664 daltons. It is the molar mass divided by the Avogadro constant, and the number in daltons is numerically the same as the molar mass in g/mol — that equivalence is what makes the mole convenient.
Is molar mass the same as molecular weight?
They are the same number in ordinary use but not the same quantity. Molecular weight, properly relative molecular mass, is a ratio and has no unit: for cholesterol it is 386.664. Molar mass carries grams per mole: 386.664 g/mol. Because the mole is defined so those agree, you can read one off the other.
Why is the molar mass not a whole number?
Because standard atomic weights are averages over the isotopes found in nature. Carbon is quoted as 12.011 rather than a whole number for that reason, and the same applies to the other elements here, which is why cholesterol comes out at 386.664 g/mol rather than 387.
Molar mass, composition and mole equivalents of cholesterol
| Element | Atoms | Atomic weight | Contribution (g/mol) | By mass |
|---|---|---|---|---|
| Carbon (C) | 27 | 12.011 | 324.297 | 83.87% |
| Hydrogen (H) | 46 | 1.008 | 46.368 | 11.99% |
| Oxygen (O) | 1 | 15.999 | 15.999 | 4.138% |
| Total — one mole of cholesterol | 386.664 | 100% |
Standard atomic weights, IUPAC 2021. The contribution column is atoms × atomic weight, and the total is the molar mass this page uses: 386.664 g/mol.
| Amount | Mass (g) | Mass (mg) | Formula units |
|---|---|---|---|
| 1 µmol | 0.000386664 | 0.386664 | 6.022e+17 |
| 10 µmol | 0.00386664 | 3.86664 | 6.022e+18 |
| 100 µmol | 0.0386664 | 38.6664 | 6.022e+19 |
| 1 mmol | 0.386664 | 386.664 | 6.022e+20 |
| 10 mmol | 3.86664 | 3866.64 | 6.022e+21 |
| 50 mmol | 19.3332 | 19,333.2 | 3.011e+22 |
| 100 mmol | 38.6664 | 38,666.4 | 6.022e+22 |
| 250 mmol | 96.666 | 96,666 | 1.506e+23 |
| 500 mmol | 193.332 | 193,332 | 3.011e+23 |
| 750 mmol | 289.998 | 289,998 | 4.517e+23 |
| 1 mol | 386.664 | 386,664 | 6.022e+23 |
| 2 mol | 773.328 | 773,328 | 1.204e+24 |
| 5 mol | 1933.32 | 1933320.000000 | 3.011e+24 |
| 10 mol | 3866.64 | 3866640.000000 | 6.022e+24 |
Mass is the amount multiplied by 386.664 g/mol. The last column is that amount multiplied by the Avogadro constant, 6.02214076 × 10²³ per mole.
| Compound | Formula | Molar mass (g/mol) | Millimoles in 1 g |
|---|---|---|---|
| Uric acid | C5H4N4O3 | 168.112 | 5.9484 |
| Glucose | C6H12O6 | 180.156 | 5.5507 |
| Aspirin | C9H8O4 | 180.159 | 5.5507 |
| Caffeine | C8H10N4O2 | 194.194 | 5.1495 |
| EDTA | C10H16N2O8 | 292.244 | 3.4218 |
| Sucrose | C12H22O11 | 342.297 | 2.9214 |
| Cholesterol (this page) | C27H46O | 386.664 | 2.5862 |
Ordered by molar mass. The last column is 1000/M, which is the number a weighed gram actually gives you.