Converting between grams and moles
The gram-to-mole conversion is the most fundamental calculation in chemistry. Every stoichiometric problem, every molarity calculation, and every yield determination starts here: divide mass by molar mass to get moles, or multiply moles by molar mass to get mass.
This calculator includes all 118 elements with their IUPAC standard atomic weights, plus 176 common compounds (acids, bases, salts, organic solvents, sugars, and metal salts) with verified molar masses. Select your substance from the dropdown and the correct molar mass is applied automatically, eliminating the most common source of error in these calculations.
How the molar mass selection works
The calculator checks three sources in order: (1) Custom Molar Mass, (2) Compound dropdown, (3) Element dropdown. It uses the first non-zero value it finds. This means if you select a compound AND an element, the compound takes priority. Set compound to “[Select Compound]” to switch to the element.
How to Calculate Moles from Grams (step by step)
Step One: Identify the molar mass
Select your substance from the Compound or Element dropdown, or enter a custom molar mass in g/mol.
molar mass = selected from dropdown or entered manually
For Silver [Ag]: molar mass = 107.868 g/mol. For Sodium chloride [NaCl]: molar mass = 58.44 g/mol.
Step Two: Divide mass by molar mass
moles = mass (g) ÷ molar mass (g/mol)
For 500 g of Silver: 500 ÷ 107.868 = 4.6353 mol. For 500 g of NaCl: 500 ÷ 58.44 = 8.5558 mol.
Step Three: Find particle count (optional)
molecules (or atoms) = moles × 6.02214076 × 10²³
For 4.6353 mol of Ag: 4.6353 × 6.022 × 10²³ = 2.791 × 10²â´ atoms.
Reverse: Moles to Grams
mass (g) = moles × molar mass (g/mol)
For 1 mol of NaCl: 1 × 58.44 = 58.44 g.
Common uses
Preparing solutions, calculating reagent amounts for reactions, determining how much product to expect from a synthesis, converting between lab measurements (grams) and chemical quantities (moles) for any stoichiometric problem.