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Stoichiometry calculator

Check atom balance, find the limiting reactant from supplied masses and calculate theoretical product yields.

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Answer

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Check atom balance, find the limiting reactant from supplied masses and calculate theoretical product yields.

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Precision and calculation record
Rounding changes displayed numbers, not the calculation. Text, fractions, matrices and CSV schedules keep their own formatting. Automatic keeps up to 12 significant digits, with money shown to cents where applicable.
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Formula and assumptions
Enter a balanced equation and one nonnegative mass per reactant in equation order. Supports ordinary neutral formulas and hydrate dots; no ionic charges, electrons, phase labels or isotope-specific material. This is theoretical complete conversion with pure reactants. It does not predict whether a reaction occurs, competing reactions, equilibrium, purity, safety or experimental yield.
Automatic precision shows numbers to 12 significant digits. Thousands separators such as 1,000 are accepted; use a dot for decimals.
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Using Stoichiometry calculator
Check atom balance, find the limiting reactant from supplied masses and calculate theoretical product yields.
Enter a balanced equation and one nonnegative mass per reactant in equation order. Supports ordinary neutral formulas and hydrate dots; no ionic charges, electrons, phase labels or isotope-specific material. This is theoretical complete conversion with pure reactants. It does not predict whether a reaction occurs, competing reactions, equilibrium, purity, safety or experimental yield.
Next: Molar mass calculator
Next: Molarity calculator
A worked example
For already-balanced equation = 2H2 + O2 -> 2H2O, reactant masses in equation order (g, comma-separated) = 4.032,32, first product theoretical yield (g) = 36.03.
Before you use the result
Enter a balanced equation and one nonnegative mass per reactant in equation order. Supports ordinary neutral formulas and hydrate dots; no ionic charges, electrons, phase labels or isotope-specific material. This is theoretical complete conversion with pure reactants. It does not predict whether a reaction occurs, competing reactions, equilibrium, purity, safety or experimental yield.
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ToolOctopus. “Stoichiometry calculator.” Updated 2026-09-29. https://tooloctopus.com/stoichiometry-calculator.
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