The molar mass of propane, C3H8, is 44.097 g/mol. That single number is what connects a mass you can weigh to an amount of substance you can react: one mole is 44.097 g, and a gram of it is 1.366e+22 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. Propane is 3 × 12.011 (C) + 8 × 1.008 (H), which is 44.097 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: 3 of the 11 atoms in a formula unit are carbon, and they account for 36.033 g of the 44.097 g, or 81.71% 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 propane is 44.097 mg and one micromole is 44.097 µg, so a balance reading to a milligram places you within 22.68 µmol. A single formula unit weighs 7.3225e-23 g, which is why the count in the gauge runs into the sextillions for any mass you can see.
Bottled gas. The molar mass is what links a cylinder weight to the energy in it, which is how barbecue and heating cylinders are actually sold. At 44.097 g/mol it is heavier than 8 of the 11 gases and small molecules covered here, and that ranking matters more than it looks: carbon dioxide has a molar mass of 44.009 g/mol, so a gram of it contains 0.2% more formula units than a gram of propane. Weigh by mass and you are not weighing equal amounts of substance.
Because this is a gas, volume is often the easier measure. One mole of any ideal gas occupies 22.414 L at 0 °C and 1 atm and 24.4655 L at 25 °C, so 44.097 g of propane — one mole — fills about 24.47 litres at room temperature. Real gases depart from that by a percent or so, more near their boiling point, but for ordinary work the molar volume is the quickest route from grams to litres.
The formula
m- The mass of propane in grams
44.097- The molar mass of propane 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 propane in grams.
- It is divided by the molar mass, 44.097 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 propane as a molecule count
0.5 g divided by 44.097 g/mol is 0.0113386 mol, and multiplying by the Avogadro constant gives 6.828e+21 formula units of propane. The same mass is 11.339 mmol, which is the figure a reaction is actually planned in.
5 g of propane as a molecule count
5 g divided by 44.097 g/mol is 0.113386 mol, and multiplying by the Avogadro constant gives 6.828e+22 formula units of propane. The same mass is 113.39 mmol, which is the figure a reaction is actually planned in.
50 g of propane as a molecule count
50 g divided by 44.097 g/mol is 1.13386 mol, and multiplying by the Avogadro constant gives 6.828e+23 formula units of propane. The same mass is 1133.9 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 propane (C3H8)?
It is 44.097 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). One mole of propane therefore weighs 44.097 g, and a gram of it is 22.677 mmol.
What percentage of propane is carbon?
81.71% by mass. Each formula unit contains 3 carbon atoms contributing 36.033 g of the 44.097 g total, so 100 g of propane contains 81.71 g of carbon and a kilogram contains 817.13 g of it.
How many molecules are in one gram of propane?
About 1.366e+22. One gram is 0.0226773 mol, and each mole contains 6.02214076 × 10²³ formula units by definition of the mole, so the count is that constant divided by 44.097.
How much does a single molecule of propane weigh?
7.3225e-23 g, which is 44.097 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 propane it is 44.097. Molar mass carries grams per mole: 44.097 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 propane comes out at 44.097 g/mol rather than 44.
Molar mass, composition and mole equivalents of propane
| Element | Atoms | Atomic weight | Contribution (g/mol) | By mass |
|---|---|---|---|---|
| Carbon (C) | 3 | 12.011 | 36.033 | 81.71% |
| Hydrogen (H) | 8 | 1.008 | 8.064 | 18.29% |
| Total — one mole of propane | 44.097 | 100% |
Standard atomic weights, IUPAC 2021. The contribution column is atoms × atomic weight, and the total is the molar mass this page uses: 44.097 g/mol.
| Amount | Mass (g) | Mass (mg) | Formula units |
|---|---|---|---|
| 1 µmol | 0.000044 | 0.044097 | 6.022e+17 |
| 10 µmol | 0.00044097 | 0.44097 | 6.022e+18 |
| 100 µmol | 0.0044097 | 4.4097 | 6.022e+19 |
| 1 mmol | 0.044097 | 44.097 | 6.022e+20 |
| 10 mmol | 0.44097 | 440.97 | 6.022e+21 |
| 50 mmol | 2.20485 | 2204.85 | 3.011e+22 |
| 100 mmol | 4.4097 | 4409.7 | 6.022e+22 |
| 250 mmol | 11.0243 | 11,024.2 | 1.506e+23 |
| 500 mmol | 22.0485 | 22,048.5 | 3.011e+23 |
| 750 mmol | 33.0727 | 33,072.8 | 4.517e+23 |
| 1 mol | 44.097 | 44,097 | 6.022e+23 |
| 2 mol | 88.194 | 88,194 | 1.204e+24 |
| 5 mol | 220.485 | 220,485 | 3.011e+24 |
| 10 mol | 440.97 | 440,970 | 6.022e+24 |
Mass is the amount multiplied by 44.097 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 |
|---|---|---|---|
| Nitrogen | N2 | 28.014 | 35.696 |
| Oxygen | O2 | 31.998 | 31.252 |
| Hydrogen peroxide | H2O2 | 34.014 | 29.4 |
| Carbon dioxide | CO2 | 44.009 | 22.723 |
| Propane (this page) | C3H8 | 44.097 | 22.677 |
| Butane | C4H10 | 58.124 | 17.205 |
| Sulfur dioxide | SO2 | 64.058 | 15.611 |
Ordered by molar mass. The last column is 1000/M, which is the number a weighed gram actually gives you.