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What does this calculator estimate?
A stoichiometry calculator converts a reactant mass into the product mass from a balanced equation. Enter the reactant mass, both molar masses, and both coefficients to calculate the theoretical product.
- moles = mass ÷ molar mass
- Mole ratio from the balanced equation
- Product mass = moles × product molar mass
How stoichiometry works
The balanced equation gives the mole ratio between reactants and products. Converting the measured mass to moles, applying the ratio, and converting back to mass gives the theoretical yield of product.
Limitations to watch for
The equation must be balanced — the coefficients are the mole ratios. The tool assumes the reactant is pure and the reaction goes to completion (no side reactions), so real yields are lower. Limiting reagents need a separate check when multiple reactants are present.
How to use it in practice
Balance the equation first and enter the correct coefficients. Convert the measured reactant mass, apply the ratio, and read the theoretical product mass. Compare to your actual yield with the percent yield calculator.
['Enter the reactant mass in grams.', 'Enter both molar masses and both coefficients.', 'The tool computes the theoretical product mass.']
How this calculator works
Formula
Product mass = (reactant mass ÷ reactant molar mass) × (product coefficient ÷ reactant coefficient) × product molar mass. The mole ratio comes from the balanced equation.
Worked example
10 g of a reactant (molar mass 20 g/mol, coefficient 1) producing a product (molar mass 44 g/mol, coefficient 1): moles = 0.50, so product mass = 0.50 × 44 = 22 g.
Assumptions to verify
- The equation is balanced with the entered coefficients.
- The reactant is pure and reacts completely.
- No side reactions or losses occur.
Frequently asked questions
What is stoichiometry?
The calculation of quantities in chemical reactions using the mole ratios from the balanced equation.
How do I convert reactant mass to product mass?
Mass → moles (÷ molar mass), apply the coefficient ratio, then moles → mass (× product molar mass). 10 g ÷ 20 = 0.5 mol → 0.5 × 44 = 22 g.
Why does the balanced equation matter?
Coefficients define how many moles of each substance react — using the wrong ratio breaks the calculation.
What is theoretical yield?
The maximum product mass from complete reaction of the given reactant, before losses.
How do I handle two reactants?
Check which is limiting (see the limiting reagent calculator) — only the limiting reagent determines the product.
What are mole ratios?
The coefficient ratios in the balanced equation: 2H₂ + O₂ → 2H₂O means 2 mol H₂ per 1 mol O₂.
Why is real yield lower?
Incomplete reactions, side products, and handling losses mean actual yield is usually below theoretical.
Cite this tool
BoringToolsKit. “Stoichiometry Calculator.” boringtoolskit.com/stoichiometry-calculator/ (reviewed 2026-08-25). Free to reference in articles, syllabi, and answer posts with a link.
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