What this grams to moles calculator does
This calculator converts a mass in grams to amount in moles using the molar mass of a substance. In chemistry, this is one of the most common conversions for stoichiometry, reaction balancing, and lab calculations.
Enter the mass of your sample and the molar mass of the compound, then click Calculate moles. The tool instantly returns your answer and shows the formula used.
Core formula for grams to moles conversion
Units:
mol = g ÷ (g/mol)
Since molar mass tells you how many grams are in 1 mole of a substance, dividing total grams by grams-per-mole gives the number of moles.
How to use the calculator correctly
Step 1: Enter grams
Input the measured mass of your sample. Use decimal values when needed (for example, 2.75 g).
Step 2: Enter molar mass
Enter molar mass in g/mol. You can use the optional compound dropdown for common substances.
Step 3: Calculate
The result is shown in moles with a clean, readable number format.
Worked examples
Example 1: Sodium chloride (NaCl)
If you have 10 g of NaCl and molar mass is 58.44 g/mol:
moles = 10 ÷ 58.44 = 0.1711 mol
Example 2: Water (H₂O)
For 36.03 g of water with molar mass 18.015 g/mol:
moles = 36.03 ÷ 18.015 = 2.000 mol
Example 3: Carbon dioxide (CO₂)
For 22 g CO₂ and molar mass 44.01 g/mol:
moles = 22 ÷ 44.01 ≈ 0.4999 mol
Common molar masses you may need
- H₂O: 18.015 g/mol
- CO₂: 44.01 g/mol
- NaCl: 58.44 g/mol
- C₆H₁₂O₆ (glucose): 180.16 g/mol
- H₂SO₄: 98.079 g/mol
- NaHCO₃: 84.0066 g/mol
Why this conversion matters in chemistry
Chemical equations are balanced in moles, not grams. That means nearly every quantitative chemistry problem starts by converting mass to moles, using mole ratios, then converting back if needed.
- Stoichiometry: determine reactant and product quantities
- Lab prep: weigh out correct amounts for solutions and reactions
- Titrations: track mole relationships accurately
- Industrial chemistry: scale reactions efficiently and safely
Tips to avoid mistakes
- Always use the correct chemical formula before finding molar mass.
- Keep units consistent: grams and g/mol.
- Use enough significant figures for intermediate steps.
- Round only at the end of the calculation.
- Double-check decimal placement for very small or large quantities.
Quick FAQ
Can I convert moles back to grams?
Yes. Use the inverse formula: grams = moles × molar mass.
What if I do not know the molar mass?
Calculate it by adding atomic masses of each atom in the compound (from the periodic table), or use a trusted chemistry database.
Does this work for elements and compounds?
Absolutely. It works for any pure substance, as long as you provide the correct molar mass.