Calculate the maximum amount of product from your reactants, and identify the limiting reagent.
Enter the mass and molecular weight of your reactant(s), plus their stoichiometric coefficients from the balanced equation. Then enter the product's molecular weight and coefficient. If you have two reactants, the calculator automatically identifies the limiting reagent and calculates the theoretical yield based on it.
For single-reactant calculations (like decomposition reactions), just leave Reactant B blank.
Theoretical yield is the maximum mass of product that could form if a reaction goes to 100% completion. The calculation involves converting reactant mass to moles (mass ÷ MW), identifying the limiting reagent (the one that runs out first based on stoichiometry), and using stoichiometric ratios to find product moles, then converting back to mass.
Worked example: React 10 g of benzaldehyde (MW = 106.12, coeff = 1) with 5 g of acetone (MW = 58.08, coeff = 1) to form dibenzalacetone (MW = 234.29, coeff = 1). Moles of benzaldehyde = 10/106.12 = 0.0942 mol. Moles of acetone = 5/58.08 = 0.0861 mol. Acetone is limiting. Theoretical yield = 0.0861 × 234.29 = 20.17 g.
In practice, actual yields are always less than theoretical due to incomplete reactions, side reactions, transfer losses, and purification steps. Percent yield = (actual yield ÷ theoretical yield) × 100%.