Stoichiometry Calculator
Calculate the mass or moles of product from a balanced chemical equation, given the reactant amount and molar masses.
Product mass
—
Moles of reactant —
Moles of product —
Assumes the reactant is fully consumed and is not the limiting factor between multiple reactants.
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How it works
moles product = moles reactant × (coefficient product ÷ coefficient reactant); mass = moles × molar massFrequently Asked Questions
How do I solve a stoichiometry problem?
Convert the given mass to moles (÷ molar mass), multiply by the mole ratio from the balanced equation's coefficients, then convert back to mass (× molar mass) for the product. For 2H₂ + O₂ → 2H₂O, 10 g of H₂ (5 mol) produces 5 mol × 1 = 5 mol H₂O, or 90 g.
Why do I need a balanced equation first?
The coefficients in a balanced equation give the exact mole ratio between substances — an unbalanced equation gives the wrong ratio and every downstream calculation will be wrong, even if the arithmetic is done perfectly.
What is a limiting reactant?
When you have two reactants, whichever runs out first caps how much product can form — the 'limiting' one. This calculator handles a single reactant-to-product conversion; compare both reactants' possible yields separately to find the limiting one.