Molar MassMolar mass of methane (CH4)
The molar mass of methane, CH4, is 16.04 g/mol. One mole of it, which is 6.022 × 1023 molecules, has a mass of 16.04 grams.
16.04 g/mol
12.011 + 4 × 1.0080 = 16.043 · 5 atoms in the formula · also called marsh gas, natural gas
About methane
Methane is the main part of natural gas and biogas and the simplest hydrocarbon. It is lighter than air.
Other names: marsh gas, natural gas.
The working
The formula CH4 has 1 carbon atom and 4 hydrogen atoms, 5 atoms in all. Multiply each count by the atomic weight of the element and add:
| Element | Atoms | Atomic weight | Total | Share by mass |
|---|---|---|---|---|
| Carbon (C) | 1 | 12.011 | 12.011 | 74.87% |
| Hydrogen (H) | 4 | 1.0080 | 4.032 | 25.13% |
12.011 + 4 × 1.0080 = 16.043 g/mol
With the rounded atomic masses used in many school books (C = 12, H = 1) the answer is 16 g/mol. The difference from 16.04 is too small to matter in most school sums.
Percentage composition
By mass, CH4 is 74.87% carbon and 25.13% hydrogen. The largest share comes from carbon. In a 100 g sample there are 74.9 g of carbon and 25.1 g of hydrogen.
Notice that hydrogen has more atoms in the formula (4) than carbon (1), yet gives a smaller share of the mass. Percentage by mass depends on how heavy each atom is, not only on how many there are.
Worked examples
Grams to moles. How many moles are in 20 g of CH4? Divide the mass by the molar mass: 20 ÷ 16.04 = 1.247 mol.
Moles to grams. What is the mass of 0.5 mol of CH4? Multiply: 0.5 × 16.04 = 8.021 g.
Counting particles. 20 g contains 1.247 mol × 6.022 × 1023 = 7.507 × 1023 molecules, and 3.754 × 1024 atoms in all.
As a gas. At 0 °C and 1 atmosphere one mole of an ideal gas occupies 22.4 litres, so the density of CH4 is about 16.04 ÷ 22.4 = 0.72 g per litre. Air averages about 29 g/mol, so this gas is lighter than air.
Quick conversion tables
| Amount | Mass |
|---|---|
| 0.1 mol | 1.604 g |
| 0.5 mol | 8.021 g |
| 1 mol | 16.04 g |
| 2 mol | 32.09 g |
| 5 mol | 80.22 g |
| Mass | Moles |
|---|---|
| 1 g | 0.06233 mol |
| 10 g | 0.6233 mol |
| 100 g | 6.233 mol |
| 1 kg | 62.33 mol |
For other amounts use the grams and moles converter.
Questions people ask
What is the molar mass of CH4?
The molar mass of methane (CH4) is 16.04 g/mol, or 16.043 g/mol before rounding, using IUPAC abridged atomic weights.
How many moles are in 100 g of CH4?
100 ÷ 16.04 = 6.233 mol.
What is the mass of one molecule of CH4?
Divide the molar mass by the Avogadro constant: 16.04 ÷ 6.022 × 1023 = 2.664 × 10-23 g.
What is the percentage of carbon in CH4?
Carbon makes up 74.87% of the mass of CH4: 1 × 12.011 ÷ 16.043 × 100.
Which values? This site uses the abridged standard atomic weights published by IUPAC (CIAAW), read on 12 November 2026. Your textbook or question paper may round them differently, for example H = 1 and O = 16, so its answer can differ slightly. In an exam, use the values the paper gives.