Theoretical Yield Calculator
Theoretical yield is the most product a reaction can possibly make from its limiting reactant. This calculator converts the limiting reactant mass to moles, applies the balanced mole ratio of product to reactant, and converts back to a product mass. Enter the limiting reactant mass and molar mass, the mole ratio from the balanced equation, and the product molar mass. Add your measured actual yield to also get the percent yield. The stoichiometry is exact; molar masses come from your own element data.
Theoretical yield formula
reactant moles = mass / reactant molar mass
product moles = reactant moles * mole ratio
theoretical yield = product moles * product molar mass
percent yield = actual / theoretical * 100
For 10 g of hydrogen (M = 2.016) forming water (M = 18.015) at a 1:1 mole ratio, the theoretical yield is about 89.36 g of water.
Stoichiometry facts
- The limiting reactant sets the maximum possible product amount.
- The mole ratio comes from the coefficients in the balanced equation.
- Theoretical yield assumes complete conversion with no losses.
- Percent yield above 100 usually indicates impurity or measurement error.
- Molar masses are sums of the average atomic masses of the constituent atoms.
Theoretical yield: frequently asked questions
What is theoretical yield?
Theoretical yield is the maximum mass of product that a reaction can form if the limiting reactant is fully converted with no losses. It is computed by converting the limiting reactant mass to moles, applying the balanced mole ratio to get product moles, then converting back to mass using the product molar mass.
How do I find the limiting reactant?
Convert each reactant mass to moles by dividing by its molar mass, then divide by its stoichiometric coefficient. The reactant with the smallest such value is the limiting reactant. Enter that reactant mass and molar mass here, along with the product-to-reactant mole ratio.
What is the mole ratio?
The mole ratio is the ratio of the product coefficient to the limiting reactant coefficient in the balanced equation. For 2 H2 plus O2 forming 2 H2O, the ratio of water to hydrogen is 2 divided by 2, equal to 1; the ratio of water to oxygen is 2 divided by 1, equal to 2.
How is percent yield calculated?
Percent yield is the actual yield divided by the theoretical yield, multiplied by 100. It measures how efficiently a reaction proceeded. Enter your measured actual yield to see the percent yield; leave it at zero to compute only the theoretical maximum.
Why might actual yield be less than theoretical?
Real reactions lose product to side reactions, incomplete conversion, transfer losses, and impurities, so actual yield is almost always below the theoretical maximum. A percent yield above 100 usually signals impure product or measurement error.
Official sources
- NIST: NIST Atomic Weights and Isotopic Compositions.
- IUPAC: IUPAC Gold Book: stoichiometry and yield.
Reviewed by the CalculatorHub team, edited by James Graham, 16 June 2026. See our methodology.