Calculate stoichiometry

Find the limiting reactant and theoretical product yield from balanced reaction inputs.

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ToolStoichiometry Calculator
Input
Output
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How it works

Masses become moles, each amount is divided by its balanced coefficient, and the smaller normalized amount identifies the limiting reactant. Product moles and mass follow that amount, with optional actual yield producing percent yield.

  • Balanced coefficients and molar masses are explicit inputs.
  • Theoretical yield assumes complete conversion and no side reactions.

Worked example

Hydrogen and nitrogen making ammonia
N2 + 3H2 -> 2NH3, from 28g of N2 and 10g of H2
Input
											Reactant amass g: 28
Reactant amolar mass gper mol: 28.02
Reactant acoefficient: 1
Reactant bmass g: 10
Reactant bmolar mass gper mol: 2.02
Reactant bcoefficient: 3
Product molar mass gper mol: 17.03
Product coefficient: 2
Output
												Reactant amoles: 0.9993
Reactant bmoles: 4.9505
Reactant amoles per coefficient: 0.9993
Reactant bmoles per coefficient: 1.6502
Limiting reagent: Reactant A
Excess reagent: Reactant B
Theoretical yield mol: 1.9986
Theoretical yield g: 34.0357
Actual yield g: 34.0357
Percent yield: 100

When to use this

Labs predict product mass, manufacturing identifies limiting feedstock, and chemistry exercises compare theoretical and actual yield.

Edge cases

  • The smallest moles-per-coefficient value limits product, not necessarily the smallest raw mass.
  • Actual yield above theoretical signals measurement or model problems.
  • Wrong coefficients produce a numerically consistent but chemically wrong answer.

References