βοΈ Theoretical Yield Calculator
Maximum product from your reactants.
How to Use This Calculator
Enter both reactant masses, their molar masses, and the balanced equation coefficients. Add your actual isolated mass to get percent yield too.
The Method
Limiting reactant gives fewer product moles
Theoretical yield = product moles x MM product
Convert each reactant to product moles through the mole ratio. The smaller result is the limiting reactant and sets the ceiling. Multiply by the product molar mass for grams.
Worked Example
10 g NaOH (40 g/mol, coef 1) + 10 g HCl (36.5 g/mol, coef 1) to NaCl (58.5 g/mol, coef 1): from NaOH: 0.25 mol product. From HCl: 0.274 mol product. NaOH limits. Theoretical = 0.25 x 58.5 = 14.6 g NaCl.
Why Actual Yield Falls Short
Even skilled chemists rarely exceed 90 percent yield. Reactions do not always go to completion, side reactions consume reactants, and product is lost in every transfer, filtration, and purification step. Recrystallization purifies but sacrifices 10 to 20 percent of material. Industrial processes obsess over yield because each lost percent is lost profit at scale.
Atom Economy
Green chemistry adds another metric: atom economy, the fraction of reactant atoms that end up in the desired product. A reaction with 100 percent yield but 30 percent atom economy still wastes most of its atoms as byproducts. The best syntheses maximize both yield and atom economy.
Excess Reactants on Purpose
Industrial processes often use excess of the cheap reactant to drive expensive reactants fully to product. The Haber process uses excess nitrogen since hydrogen costs more to make. Excess also pushes equilibrium forward by Le Chatelier's principle, raising both yield and rate in reversible reactions.
Scaling to Industry
Lab yields rarely survive scale-up unchanged: mixing, heat transfer, and separation all behave differently in a 10,000-liter reactor versus a flask. Pilot plants bridge the gap, and engineers derate lab yields by 5 to 15 percent when designing production. This is why process chemistry is its own discipline.
Frequently Asked Questions
What is theoretical yield?
The maximum product mass possible if the limiting reactant converts completely with no losses. It comes straight from stoichiometry: moles of limiting reactant times the mole ratio times product molar mass.
How is theoretical yield different from actual yield?
Actual yield is what you really isolate, always lower due to incomplete reaction, side reactions, and transfer losses. Percent yield = actual / theoretical x 100.
What is the limiting reactant?
The reactant that runs out first and caps the product. Find it by converting each reactant to moles of product; the smallest result wins. This calculator identifies it automatically.
Can percent yield exceed 100 percent?
In theory no, but it happens with wet or impure product, weighing errors, or unreacted starting material mixed in. Over 100 percent signals a measurement problem, not a miracle.
Why do I need the balanced equation?
Coefficients give the mole ratios that convert between reactants and products. Without them you cannot connect grams of reactant to grams of product. Balance first, then calculate.