Grams to Moles Calculator
Convert mass in grams to moles using the molecular weight of your substance. Formula: n = mass ÷ MW.
How to Convert Grams to Moles
- Find the molecular weight (MW) of your substance from the periodic table or the table below.
- Divide the mass in grams by the molecular weight.
- The result is the number of moles.
Example: How many moles are in 10 g of NaCl?
n = 10 g ÷ 58.44 g/mol = 0.1711 mol
Grams to Moles Formula
Where:
- n = number of moles (mol)
- m = mass (grams)
- MW = molecular weight (g/mol)
Common Molecular Weights
Click any row to use that molecular weight in the calculator above.
| Compound | Formula | MW (g/mol) |
|---|---|---|
| Water | H₂O | 18.015 |
| Sodium chloride | NaCl | 58.44 |
| Sodium hydroxide | NaOH | 40.00 |
| Hydrochloric acid | HCl | 36.46 |
| Sulfuric acid | H₂SO₄ | 98.08 |
| Nitric acid | HNO₃ | 63.01 |
| Glucose | C₆H₁₂O₆ | 180.16 |
| Ethanol | C₂H₅OH | 46.07 |
| Acetic acid | CH₃COOH | 60.05 |
| Carbon dioxide | CO₂ | 44.01 |
| Calcium carbonate | CaCO₃ | 100.09 |
| Sucrose | C₁₂H₂₂O₁₁ | 342.30 |
What is a Mole?
A mole is the SI unit for amount of substance. One mole contains exactly 6.022 × 10²³ particles (atoms, molecules, or ions) — this is Avogadro's number.
The mole bridges the atomic scale (individual molecules, too small to weigh) to the laboratory scale (grams you can measure on a balance). It lets chemists relate mass to the number of particles in a sample.
Grams, Moles, and Molarity
Once you know how many moles are in your sample, you can calculate molarity (molar concentration) if you know the volume of solution. Molarity = moles ÷ volume (L).
Use our Molarity Calculator to compute solution concentrations directly from mass, MW, and volume.
Frequently Asked Questions
How do I convert grams to moles?
Divide the mass in grams by the molecular weight in g/mol. Formula: n = mass ÷ MW.
Example: 10 g NaCl ÷ 58.44 g/mol = 0.171 mol.
What is molecular weight?
Molecular weight is the mass of one mole of a substance in g/mol. It is found by summing the atomic masses of all atoms in the molecule from the periodic table.
Example: NaCl = 22.99 (Na) + 35.45 (Cl) = 58.44 g/mol.
How many moles is 1 gram?
It depends on the substance:
- Water (MW 18.015): 1 g = 0.0555 mol
- NaCl (MW 58.44): 1 g = 0.0171 mol
- Glucose (MW 180.16): 1 g = 0.00555 mol
Lighter molecules have more moles per gram.
What is Avogadro's number?
6.022 × 10²³ — the number of particles (atoms, molecules, ions) in one mole of a substance. Named after the Italian scientist Amedeo Avogadro.
How do I find molecular weight?
Sum the atomic masses of all atoms in the chemical formula using the periodic table. For common compounds, use our molecular weights table above. For complex molecules, use a dedicated molar mass calculator.
Related Chemistry Tools
- Moles to Grams Calculator — reverse conversion
- Empirical Formula Calculator — find empirical and molecular formulas from percent composition
- Molar Mass Calculator
- Molarity Calculator — uses moles + volume to compute concentration
- Equation Balancer — balance chemical equations
- PPM to mg/L Converter
- All Chemistry Calculators
All calculations on CoolConversion use formulas and constants documented by internationally recognised standards bodies (such as IUPAC and NIST).
