The molar mass of methane, CH4, is 16.043 g/mol. That single number is what connects a mass you can weigh to an amount of substance you can react: one mole is 16.043 g, and a gram of it is 3.754e+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. Methane is 12.011 (C) + 4 × 1.008 (H), which is 16.043 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: 1 of the 5 atoms in a formula unit is carbon, and they account for 12.011 g of the 16.043 g, or 74.87% 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 methane is 16.043 mg and one micromole is 16.043 µg, so a balance reading to a milligram places you within 62.33 µmol. A single formula unit weighs 2.6640e-23 g, which is why the count in the gauge runs into the sextillions for any mass you can see.
Natural gas, and the lightest hydrocarbon. Its molar mass is what makes gas billing in cubic metres and in kilograms two different quantities. At 16.043 g/mol it is the lightest of the 11 gases and small molecules covered here, and that ranking matters more than it looks: ammonia has a molar mass of 17.031 g/mol, so a gram of it contains 5.8% fewer formula units than a gram of methane. 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 16.043 g of methane — 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 methane in grams
16.043- The molar mass of methane 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 methane in grams.
- It is divided by the molar mass, 16.043 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 methane as a molecule count
0.5 g divided by 16.043 g/mol is 0.0311662 mol, and multiplying by the Avogadro constant gives 1.877e+22 formula units of methane. The same mass is 31.166 mmol, which is the figure a reaction is actually planned in.
5 g of methane as a molecule count
5 g divided by 16.043 g/mol is 0.311662 mol, and multiplying by the Avogadro constant gives 1.877e+23 formula units of methane. The same mass is 311.66 mmol, which is the figure a reaction is actually planned in.
50 g of methane as a molecule count
50 g divided by 16.043 g/mol is 3.11662 mol, and multiplying by the Avogadro constant gives 1.877e+24 formula units of methane. The same mass is 3116.6 mmol, which is the figure a reaction is actually planned in.
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Frequently asked questions
What is the molar mass of methane (CH4)?
It is 16.043 g/mol. That is the sum of the standard atomic weights of every atom in the formula: 12.011 (C) + 4 × 1.008 (H). One mole of methane therefore weighs 16.043 g, and a gram of it is 62.332 mmol.
What percentage of methane is carbon?
74.87% by mass. Each formula unit contains 1 carbon atom contributing 12.011 g of the 16.043 g total, so 100 g of methane contains 74.87 g of carbon and a kilogram contains 748.68 g of it.
How many molecules are in one gram of methane?
About 3.754e+22. One gram is 0.0623325 mol, and each mole contains 6.02214076 × 10²³ formula units by definition of the mole, so the count is that constant divided by 16.043.
How much does a single molecule of methane weigh?
2.6640e-23 g, which is 16.043 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 methane it is 16.043. Molar mass carries grams per mole: 16.043 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 methane comes out at 16.043 g/mol rather than 16.
Molar mass, composition and mole equivalents of methane
| Element | Atoms | Atomic weight | Contribution (g/mol) | By mass |
|---|---|---|---|---|
| Carbon (C) | 1 | 12.011 | 12.011 | 74.87% |
| Hydrogen (H) | 4 | 1.008 | 4.032 | 25.13% |
| Total — one mole of methane | 16.043 | 100% |
Standard atomic weights, IUPAC 2021. The contribution column is atoms × atomic weight, and the total is the molar mass this page uses: 16.043 g/mol.
| Amount | Mass (g) | Mass (mg) | Formula units |
|---|---|---|---|
| 1 µmol | 0.000016 | 0.016043 | 6.022e+17 |
| 10 µmol | 0.00016043 | 0.16043 | 6.022e+18 |
| 100 µmol | 0.0016043 | 1.6043 | 6.022e+19 |
| 1 mmol | 0.016043 | 16.043 | 6.022e+20 |
| 10 mmol | 0.16043 | 160.43 | 6.022e+21 |
| 50 mmol | 0.80215 | 802.15 | 3.011e+22 |
| 100 mmol | 1.6043 | 1604.3 | 6.022e+22 |
| 250 mmol | 4.01075 | 4010.75 | 1.506e+23 |
| 500 mmol | 8.0215 | 8021.5 | 3.011e+23 |
| 750 mmol | 12.0322 | 12,032.2 | 4.517e+23 |
| 1 mol | 16.043 | 16,043 | 6.022e+23 |
| 2 mol | 32.086 | 32,086 | 1.204e+24 |
| 5 mol | 80.215 | 80,215 | 3.011e+24 |
| 10 mol | 160.43 | 160,430 | 6.022e+24 |
Mass is the amount multiplied by 16.043 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 |
|---|---|---|---|
| Methane (this page) | CH4 | 16.043 | 62.332 |
| Ammonia | NH3 | 17.031 | 58.716 |
| Water | H2O | 18.015 | 55.509 |
| Carbon monoxide | CO | 28.01 | 35.702 |
| Nitrogen | N2 | 28.014 | 35.696 |
| Oxygen | O2 | 31.998 | 31.252 |
| Hydrogen peroxide | H2O2 | 34.014 | 29.4 |
Ordered by molar mass. The last column is 1000/M, which is the number a weighed gram actually gives you.