Molecular Weight Calculator · Practical guide
How Many Grams Are in a Mole?
A mole of any substance weighs its molar mass in grams — the number depends on the substance.
At a glance
The Short Answer
There is no single answer: one mole of a substance weighs exactly its molar mass in grams, and that value is different for every compound. One mole of water is 18.015 g, one mole of NaCl is 58.44 g, and one mole of glucose is 180.156 g — each containing the same 6.022 × 10^23 particles.
Interactive tool
Molecular Weight Calculator
Enter your own values, then compare the result with the examples below.
Results
| Element | Atomic Weight | Count | Total |
|---|
Grams per Mole of Common Compounds
| Substance | Formula | Molar Mass | Mass of 1 Mole |
|---|---|---|---|
| Water | H2O | 18.015 g/mol | 18.015 g |
| Carbon dioxide | CO2 | 44.009 g/mol | 44.009 g |
| Sodium chloride | NaCl | 58.44 g/mol | 58.44 g |
| Calcium carbonate | CaCO3 | 100.086 g/mol | 100.086 g |
| Glucose | C6H12O6 | 180.156 g/mol | 180.156 g |
Why the Number Varies
A mole is a count, not a weight — like a dozen. A dozen eggs and a dozen bowling balls both contain twelve items but weigh very different amounts. Heavier atoms and bigger molecules make a heavier mole.
Converting Both Ways
Multiply moles by molar mass to get grams: 2.5 mol of CO2 × 44.009 = 110.02 g. Divide grams by molar mass to get moles: 100 g of CO2 ÷ 44.009 = 2.272 mol. Find the molar mass of any formula with the calculator above, then apply the single multiplication or division.
Frequently Asked Questions
How many grams are in a mole of carbon?
12.011 g, the atomic weight of carbon expressed in grams. For elements, the molar mass is simply the periodic table value with units of g/mol.
Is a mole of every gas the same volume?
At the same temperature and pressure, yes — about 22.4 L per mole at standard temperature and pressure, regardless of which gas it is. The masses still differ.
How many molecules are in one mole?
6.022 × 10^23, known as Avogadro's number. It is defined so that one mole of a substance weighs its molecular weight in grams.
How do I find grams for a fraction of a mole?
Multiply the molar mass by the fraction. A quarter mole of NaCl is 0.25 × 58.44 = 14.61 g.