Theoretical Yield Calculator with Steps
Enter a balanced equation and the available reactants in grams or moles. Find the limiting reactant, the maximum product amount, and percent yield when you have an actual product mass.
Calculate theoretical yield
Start with a balanced reaction, then enter each reactant amount. The calculator checks atom balance and finds the limiting reactant.
Assumes pure reactants and complete conversion in the entered reaction. It does not model equilibrium, side reactions, purity, or experimental loss. Round the result to the precision justified by your measurements.
Read the limiting reagent guideFrom a balanced equation to product mass
The calculator uses the coefficients in your reaction as mole ratios. It first checks that the number of atoms of each element matches on both sides. Each entered mass is divided by its formula’s molar mass; quantities already in moles need no conversion. It then compares the moles available per stoichiometric coefficient.
Why the limiting reactant controls the answer
The smallest value of n ÷ coefficient determines how far the reaction can proceed. Multiplying this amount by the selected product coefficient gives theoretical product moles. Multiplying again by the product’s molar mass gives grams. If two reactants provide the same limiting amount, both are identified as co-limiting.
- Enter an amount for every measured reactant.
- Use “Known excess” only when the problem explicitly gives that condition.
- At least one reactant needs a numerical amount.
- Choose the product you want when the equation has more than one.
Worked example: hydrogen and oxygen
For 2H2 + O2 → 2H2O, enter 4.032 g H2 and 31.998 g O2. These quantities correspond to 2 mol H2 and 1 mol O2. Dividing by their coefficients gives 1 mol of reaction for each, so they are present in stoichiometric amounts. The result is 2 mol H2O, or 36.03 g using the calculator’s atomic masses.
Actual yield and percent yield
Actual yield is the product amount measured after the experiment. When you enter actual product mass, percent yield is actual mass divided by theoretical mass, multiplied by 100. A result above 100% is a prompt to check measurements, units, contamination, or retained moisture; it is not evidence that the theoretical maximum was exceeded.
What this calculation assumes
The result assumes pure reactants and complete conversion according to the equation. It does not predict equilibrium, side reactions, or handling losses. Use neutral molecular formulas with whole-number reaction coefficients; ionic equations and reactions requiring isotope-specific masses are outside this tool’s scope. Preserve full precision through the calculation and round your final answer to match the measurements.
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Frequently Asked Questions
How do I calculate theoretical yield?
Balance the reaction, convert reactant quantities to moles, and divide each amount by its coefficient. The smallest result sets the reaction amount. Multiply it by the product coefficient and then the product molar mass to obtain grams.
Does the calculator find the limiting reactant?
Yes. It compares the available moles per coefficient for every measured reactant. Reactants marked “Known excess” are assumed sufficient and do not set the limit.
Can I enter moles instead of grams?
Yes. Choose grams or moles separately for each reactant. The product result shows both moles and grams.
Will it balance my equation automatically?
No. It checks atom balance and explains which elements are unbalanced. Use the linked chemical equation balancer first, then enter the balanced equation here.
Why is my percent yield over 100 percent?
Check product dryness, contamination, units, and measured masses. The theoretical calculation assumes a pure product and the stated reaction, so a larger measured mass needs investigation.
Continue in the app
Use Chemistry AI: Chymia for the full guided result after this quick check.
