The molar mass of glycerol, C3H8O3, is 92.094 g/mol. That single number is what connects a mass you can weigh to an amount of substance you can react: one mole is 92.094 g, and a gram of it is 6.539e+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. Glycerol is 3 × 12.011 (C) + 8 × 1.008 (H) + 3 × 15.999 (O), which is 92.094 g/mol, taking standard atomic weights, and every page here computes that sum rather than quoting it. Oxygen makes up the largest share of the mass: 3 of the 14 atoms in a formula unit are oxygen, and they account for 47.997 g of the 92.094 g, or 52.12% 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 glycerol is 92.094 mg and one micromole is 92.094 µg, so a balance reading to a milligram places you within 10.86 µmol. A single formula unit weighs 1.5293e-22 g, which is why the count in the gauge runs into the sextillions for any mass you can see.
Glycerine: a humectant in food and cosmetics, a cryoprotectant, and the backbone of every triglyceride. Sold as a 99.5% syrup. At 92.094 g/mol it is heavier than 8 of the 21 organic compounds covered here, and that ranking matters more than it looks: benzene has a molar mass of 78.114 g/mol, so a gram of it contains 17.9% more formula units than a gram of glycerol. Weigh by mass and you are not weighing equal amounts of substance.
Purity is the usual gap between the calculation and the balance. A reagent sold at 98% means 1.8419 g of a nominal 92.094 g is something else, so for exact work you divide the weighed mass by the assay figure on the certificate. For most purposes the difference is smaller than the error in reading the meniscus, but it is systematic rather than random, so it does not average out.
The formula
m- The mass of glycerol in grams
92.094- The molar mass of glycerol 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 glycerol in grams.
- It is divided by the molar mass, 92.094 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 glycerol as a molecule count
0.5 g divided by 92.094 g/mol is 0.00542924 mol, and multiplying by the Avogadro constant gives 3.27e+21 formula units of glycerol. The same mass is 5.4292 mmol, which is the figure a reaction is actually planned in.
5 g of glycerol as a molecule count
5 g divided by 92.094 g/mol is 0.0542924 mol, and multiplying by the Avogadro constant gives 3.27e+22 formula units of glycerol. The same mass is 54.292 mmol, which is the figure a reaction is actually planned in.
50 g of glycerol as a molecule count
50 g divided by 92.094 g/mol is 0.542924 mol, and multiplying by the Avogadro constant gives 3.27e+23 formula units of glycerol. The same mass is 542.92 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 glycerol (C3H8O3)?
It is 92.094 g/mol. That is the sum of the standard atomic weights of every atom in the formula: 3 × 12.011 (C) + 8 × 1.008 (H) + 3 × 15.999 (O). One mole of glycerol therefore weighs 92.094 g, and a gram of it is 10.858 mmol.
What percentage of glycerol is oxygen?
52.12% by mass. Each formula unit contains 3 oxygen atoms contributing 47.997 g of the 92.094 g total, so 100 g of glycerol contains 52.12 g of oxygen and a kilogram contains 521.17 g of it.
How many molecules are in one gram of glycerol?
About 6.539e+21. One gram is 0.0108585 mol, and each mole contains 6.02214076 × 10²³ formula units by definition of the mole, so the count is that constant divided by 92.094.
How much does a single molecule of glycerol weigh?
1.5293e-22 g, which is 92.094 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 glycerol it is 92.094. Molar mass carries grams per mole: 92.094 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. Oxygen is quoted as 15.999 rather than a whole number for that reason, and the same applies to the other elements here, which is why glycerol comes out at 92.094 g/mol rather than 92.
Molar mass, composition and mole equivalents of glycerol
| Element | Atoms | Atomic weight | Contribution (g/mol) | By mass |
|---|---|---|---|---|
| Oxygen (O) | 3 | 15.999 | 47.997 | 52.12% |
| Carbon (C) | 3 | 12.011 | 36.033 | 39.13% |
| Hydrogen (H) | 8 | 1.008 | 8.064 | 8.756% |
| Total — one mole of glycerol | 92.094 | 100% |
Standard atomic weights, IUPAC 2021. The contribution column is atoms × atomic weight, and the total is the molar mass this page uses: 92.094 g/mol.
| Amount | Mass (g) | Mass (mg) | Formula units |
|---|---|---|---|
| 1 µmol | 0.000092 | 0.092094 | 6.022e+17 |
| 10 µmol | 0.00092094 | 0.92094 | 6.022e+18 |
| 100 µmol | 0.0092094 | 9.2094 | 6.022e+19 |
| 1 mmol | 0.092094 | 92.094 | 6.022e+20 |
| 10 mmol | 0.92094 | 920.94 | 6.022e+21 |
| 50 mmol | 4.6047 | 4604.7 | 3.011e+22 |
| 100 mmol | 9.2094 | 9209.4 | 6.022e+22 |
| 250 mmol | 23.0235 | 23,023.5 | 1.506e+23 |
| 500 mmol | 46.047 | 46,047 | 3.011e+23 |
| 750 mmol | 69.0705 | 69,070.5 | 4.517e+23 |
| 1 mol | 92.094 | 92,094 | 6.022e+23 |
| 2 mol | 184.188 | 184,188 | 1.204e+24 |
| 5 mol | 460.47 | 460,470 | 3.011e+24 |
| 10 mol | 920.94 | 920,940 | 6.022e+24 |
Mass is the amount multiplied by 92.094 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 |
|---|---|---|---|
| Ethylene glycol | C2H6O2 | 62.068 | 16.111 |
| Glycine | C2H5NO2 | 75.067 | 13.321 |
| Benzene | C6H6 | 78.114 | 12.802 |
| Glycerol (this page) | C3H8O3 | 92.094 | 10.858 |
| Toluene | C7H8 | 92.141 | 10.853 |
| Creatinine | C4H7N3O | 113.12 | 8.8402 |
| Octane | C8H18 | 114.232 | 8.7541 |
Ordered by molar mass. The last column is 1000/M, which is the number a weighed gram actually gives you.