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📘 About the Grams ↔ Moles
The mole is the chemist's way of counting particles. One mole contains Avogadro's number, 6.022 × 10²³, of atoms, molecules or ions. This mole calculator converts between mass in grams and amount in moles using the molar mass.
It also gives the number of particles and, if the substance is a gas, its volume at standard temperature and pressure (STP). NCERT now uses STP as 0 °C and 1 bar (22.7 L/mol); older books use 1 atm (22.4 L/mol), so both are shown.
🧮 Formula
Particles can mean atoms, molecules or formula units depending on the substance — be clear which one a question asks for.
✏️ Worked examples
36 g of water
You get| Amount (mol) | 1.99833 |
| Mass (g) | 36 |
| Number of particles | 1.20343e24 |
| Volume if a gas, at STP 0 °C & 1 bar (L) | 45.3842 |
| Volume if a gas, at 0 °C & 1 atm (L) | 44.7907 |
36 g of water is 1.99833 mol, containing 1.20343e24 molecules.
Try this example →Mass of 0.5 mol of NaCl
You get| Amount (mol) | 0.5 |
| Mass (g) | 29.22 |
| Number of particles | 3.01107e23 |
| Volume if a gas, at STP 0 °C & 1 bar (L) | 11.3555 |
| Volume if a gas, at 0 °C & 1 atm (L) | 11.207 |
0.5 mol of sodium chloride has a mass of 29.22 g.
Try this example →🧭 How to use this calculator
What you enter
- FindPick what you want to find. The box for that quantity is ignored, so you can leave any number in it.
- Mass (m) (g)
- Molar mass (M) (g/mol)Not sure? Use the molar mass calculator.
- Amount (n) (mol)
What you get
- Amount (mol)
- Mass (g)
- Number of particles
- Volume if a gas, at STP 0 °C & 1 bar (L)
- Volume if a gas, at 0 °C & 1 atm (L)
💡 The mole map
- Mass (g) ÷ molar mass → moles
- Moles × molar mass → mass (g)
- Moles × 6.022 × 10²³ → particles
- Particles ÷ 6.022 × 10²³ → moles
- Moles × 22.7 L → gas volume at STP
❓ Frequently asked questions
How do you convert grams to moles?
Divide the mass in grams by the molar mass: n = m/M. 36 g of water ÷ 18 g/mol = 2 mol.
What is Avogadro's number?
6.02214076 × 10²³, the number of particles in one mole.
What is the volume of 1 mole of gas at STP?
22.7 L at 0 °C and 1 bar (current IUPAC/NCERT), or 22.4 L at 0 °C and 1 atm (older definition).
How many molecules are in 1 g of water?
1 ÷ 18.015 × 6.022 × 10²³ ≈ 3.34 × 10²² molecules.