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Theoretical Yield Calculator: How to Calculate Theoretical Yield

Calculate theoretical yield and percent yield in chemistry using stoichiometric mole ratios, limiting reactant mass, and molar masses.

Direct Answer (How to calculate theoretical yield?): Convert limiting reactant mass to moles by dividing by its molar mass: Moles = Mass ÷ Molar Mass. Then multiply by the stoichiometric mole ratio: Moles of Product = Moles of Reactant × (Product Coefficient ÷ Reactant Coefficient). Finally, multiply product moles by product molar mass: Theoretical Yield (g) = Moles of Product × Molar Mass of Product. To find percent yield, calculate: (Actual Yield ÷ Theoretical Yield) × 100%.

Reaction Stoichiometry

How to calculate theoretical yield: 3-step formula guide

Theoretical yield is the maximum mass of product that can be generated in a chemical reaction assuming 100% conversion of the limiting reactant with no product loss.

Step 1: Calculate moles of the limiting reactant

Moles of Reactant = Mass of Reactant (g) ÷ Molar Mass of Reactant (g/mol)

For 10.0 grams of Methanol (CH₃OH, molar mass = 32.04 g/mol): 10.0 ÷ 32.04 = 0.31211 mol.

Step 2: Apply the stoichiometric mole ratio

Moles of Product = Moles of Reactant × (Product Stoichiometric Coefficient ÷ Reactant Stoichiometric Coefficient)

If 1 mole of reactant yields 1 mole of product, the theoretical moles of product equals 0.31211 mol.

Step 3: Convert product moles to grams

Theoretical Yield (g) = Moles of Product × Molar Mass of Product (g/mol)

If the desired product has a molar mass of 60.05 g/mol: 0.31211 × 60.05 = 18.742 grams.

How to calculate percent yield

Percent Yield (%) = (Actual Yield in lab ÷ Theoretical Yield) × 100%

If your reaction in the laboratory yielded 15.20 grams of purified product: (15.20 ÷ 18.742) × 100% = 81.10%.

Common chemistry molar masses reference table

Chemical SubstanceFormulaMolar Mass (g/mol)Common Role
WaterH₂O18.015Solvent / Common Byproduct
Carbon DioxideCO₂44.010Combustion Product
GlucoseC₆H₁₂O₆180.156Biological Substrate / Sugar
Sodium ChlorideNaCl58.440Table Salt / Precipitation Product
Aspirin (Acetylsalicylic Acid)C₉H₈O₄180.157Classic Organic Synthesis Product
Salicylic AcidC₇H₆O₃138.121Limiting Reactant in Aspirin Synthesis
Standard IUPAC molar masses frequently used in general and organic chemistry experiments.

Frequently asked questions about theoretical yield

What is a limiting reactant?

The limiting reactant (or limiting reagent) is the substance that is completely consumed first in a chemical reaction. Because the reaction stops once this reactant is exhausted, it strictly dictates and limits the theoretical yield of product.

Why is my percent yield higher than 100%?

A percent yield above 100% is physically impossible under the Law of Conservation of Mass. If your calculation yields >100%, it indicates that the final product was not completely dry (residual solvent weight) or contains unreacted starting materials/impurities.

How does theoretical yield differ from actual yield?

Theoretical yield is a paper calculation showing the mathematical maximum product possible. Actual yield is the exact physical mass measured on an analytical balance after running the experiment and purifying the substance.

Created and chemistry-verified by Velour Trends · Updated 9 November 2026. Standard IUPAC stoichiometry formulas. Report a calculation issue.

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