Theoretical Yield Calculator
Calculate the maximum theoretical yield of a chemical reaction from a balanced equation, reactant amount, mole ratio, and molar mass. The calculator can use one known reactant or compare multiple reactants to find the limiting reactant first.
How to Use the Theoretical Yield Calculator
Enter the reaction, choose the reactant amount you know, then choose the product whose maximum yield you want. The tool balances the equation before it reads the mole ratio.
Step 1
Enter the chemical equation
Type H2 + O2 -> H2O, N2 + H2 -> NH3, CaCO3 -> CaO + CO2, or another neutral equation. The calculator balances it automatically.
Step 2
Choose the reactant setup
Use one reactant when the other reactants are in excess. Compare reactants when the problem gives two or more starting amounts.
Step 3
Pick the product and unit
Choose the target product from the balanced equation and report theoretical yield in g, mg, kg, or mol.
Step 4
Read the steps
Review balanced equation, limiting reactant if needed, mole ratio, molar masses, final yield, and dimensional analysis.
How to Calculate Theoretical Yield
Theoretical yield is a stoichiometry path from a known reactant to a product. The balanced equation controls the mole ratio; molar mass only converts between grams and moles.
Start by treating the balanced equation as a recipe written in moles, not in grams. A coefficient of 2 in front of H₂ means 2 moles of H₂, not 2 grams of H₂. That is why theoretical yield calculations must pass through moles before they can predict a product mass.
If the problem gives only one reactant amount, the usual classroom assumption is that every other reactant is available in excess. If the problem gives amounts for two or more reactants, first compare the available reaction extent for each reactant. The smallest extent is the limiting reactant, and it alone determines the maximum product amount.
1Balance the chemical equation
Coefficients must conserve every atom. For H₂ + O₂ -> H₂O, the balanced equation is 2H₂ + O₂ → 2H₂O, so the useful ratio is 2 mol H₂ : 2 mol H₂O.
2Convert reactants to moles
If a reactant is given in grams, divide by that reactant's own molar mass. Do not compare grams of different substances directly, because 4 g H₂ and 4 g H₂O contain very different numbers of particles.
3Identify the limiting reactant if necessary
When two or more reactant amounts are supplied, divide each mole amount by its coefficient. The smallest value is the available reaction extent and limits product formation.
4Use the mole ratio to find product moles
Multiply limiting reactant moles by product coefficient ÷ reactant coefficient, or multiply reaction extent by the product coefficient. This is the stoichiometric core of theoretical yield.
5Convert product moles to grams
If the answer needs grams, multiply product moles by the product molar mass. Then convert grams to mg or kg if requested and round the final theoretical yield.
Theoretical Yield Formula
For a one-reactant mass-to-mass problem, combine the grams-to-moles conversion, the coefficient ratio, and the product molar mass into one expression.
Mass-to-mass formula
theoretical yield (g) = reactant mass ÷ reactant molar mass × product coefficient / reactant coefficient × product molar mass
Symbol form
m_product = m_reactant / M_reactant × ν_product / ν_reactant × M_product
How to Calculate Theoretical Yield in Grams
Grams appear at the end of the calculation. The mole ratio predicts moles of product first; multiplying by product molar mass turns that amount into a mass.
Last conversion
grams product = moles product × molar mass product
Short example
1.984 mol H₂O × 18.015 g/mol = 35.74 g H₂O
If the problem asks for milligrams or kilograms, calculate grams first and convert at the end. Keeping the mole-ratio step in moles and the mass step in grams avoids the common mistake of multiplying a gram amount directly by a coefficient ratio.
What Is Theoretical Yield in Chemistry?
Theoretical yield is the maximum amount of product predicted by stoichiometry when a reaction proceeds ideally.
In chemistry, theoretical yield is a calculated upper limit. It answers: if the balanced reaction goes as written and the available reactants are used perfectly, how much product could form? The answer is based on atom conservation and mole ratios, not on a lab measurement.
The balanced chemical equation supplies the stoichiometric coefficients. Those coefficients compare moles of reactants and products. Molar mass then converts between the masses measured on a balance and the moles used by the equation.
If only one reactant amount is given, textbook problems usually assume every other reactant is present in excess. If several reactant amounts are given, the theoretical yield must be based on the limiting reactant, because that reactant runs out first and stops further product formation.
Actual lab yield is usually lower than theoretical yield. Side reactions, incomplete conversion, equilibrium limits, impurities, spills, filtration loss, and product left on glassware all reduce the collected amount. That is why theoretical yield is the reference point for percent yield, but it is not the same thing as actual yield.
Theoretical Yield vs Actual Yield
Theoretical yield predicts the ideal maximum; actual yield is what the experiment produces.
| Term | Meaning |
|---|---|
| Theoretical yield | Maximum predicted by stoichiometry |
| Actual yield | Product actually obtained experimentally |
| Percent yield | Actual ÷ theoretical × 100% |
Need Percent Yield?
Theoretical yield gives the predicted maximum product amount. If you also know the actual yield from a lab, use it next to calculate percent yield: actual ÷ theoretical × 100%.
How the Limiting Reactant Determines Theoretical Yield
A reaction cannot make more product after one required reactant is gone. That is why theoretical yield is controlled by the limiting reactant whenever multiple starting amounts are known.
Stage 1
Reactant A
Stage 2
Reactant B
Stage 3
Find limiting reactant
Stage 4
Maximum product
Limiting-reactant comparison
reaction extent = moles reactant ÷ balanced coefficient smallest reaction extent → limiting reactant limiting extent × product coefficient → product moles
The comparison must use moles divided by coefficients, not just the smallest gram amount. A smaller mass can still contain more moles if the substance has a low molar mass, and a reactant with a larger coefficient is consumed faster per reaction event.
For a full excess-reactant and leftover-mass breakdown, open the limiting reactant calculator. For this problem type, the final answer is the maximum product amount.
Theoretical Yield Examples
These examples cover simple one-reactant yield, limiting-reactant yield, and a decomposition reaction that connects to molar-mass pages.
Example 1 — H₂ + O₂ → H₂O
2H₂ + O₂ → 2H₂O
4.00 g H₂ gives 35.74 g H₂O
Key values for Example 1 — H₂ + O₂ → H₂O Given 4.00 g H₂ Molar mass H₂ = 2.016 g/mol; H₂O = 18.015 g/mol Mole ratio 2 mol H₂ : 2 mol H₂O Final yield 35.74 g H₂O - 14.00 g H₂ ÷ 2.016 g/mol = 1.984 mol H₂.
- 2The H₂:H₂O mole ratio is 2:2, so 1.984 mol H₂ makes 1.984 mol H₂O.
- 31.984 mol H₂O × 18.015 g/mol = 35.74 g H₂O.
Example 2 — N₂ + H₂ → NH₃
N₂ + 3H₂ → 2NH₃
28.0 g N₂ and 3.00 g H₂ gives 16.9 g NH₃
Key values for Example 2 — N₂ + H₂ → NH₃ Given 28.0 g N₂ and 3.00 g H₂ Balanced equation N₂ + 3H₂ → 2NH₃ Limiting check H₂ has the smaller n ÷ coefficient value Final yield 16.9 g NH₃ - 128.0 g N₂ is about 0.999 mol N₂; 3.00 g H₂ is about 1.488 mol H₂.
- 2Compare n ÷ coefficient: N₂ ≈ 0.999 and H₂ ≈ 0.496, so H₂ is limiting.
- 30.496 reaction extent × 2 mol NH₃ × 17.031 g/mol = about 16.9 g NH₃.
Example 3 — CaCO₃ → CaO + CO₂
CaCO₃ → CaO + CO₂
100.09 g CaCO₃ gives about 44.01 g CO₂
Key values for Example 3 — CaCO₃ → CaO + CO₂ Given 100.09 g CaCO₃ Balanced equation CaCO₃ → CaO + CO₂ Mole ratio 1 mol CaCO₃ : 1 mol CO₂ Final yield about 44.01 g CO₂ - 1The balanced equation is already 1:1:1.
- 2100.09 g CaCO₃ is about 1 mol CaCO₃.
- 3The 1:1 mole ratio gives about 1 mol CO₂, or about 44.01 g CO₂.
Molar mass of CaCO₃Molar mass of CO₂
Try This Example →
Related Chemistry Calculators
Theoretical yield sits after equation balancing, molar mass, stoichiometry, and limiting-reactant logic in the calculation chain.
- Limiting Reactant CalculatorFind which reactant runs out first and which reactant remains in excess.
- Stoichiometry CalculatorConvert one known substance into another reactant or product amount.
- Chemical Equation BalancerBalance equations before reading coefficients and mole ratios.
- Molar Mass CalculatorFind the molar masses used in gram-to-mole and mole-to-gram steps.
- Grams to Moles CalculatorConvert a single substance between mass and moles without a reaction.
Frequently Asked Questions
What is theoretical yield?
Theoretical yield is the maximum amount of product predicted by stoichiometry for an ideal reaction. It comes from the balanced chemical equation, the available reactant amount, mole ratios, and product molar mass. In a real lab, actual yield is usually lower because reactions may be incomplete or product may be lost during transfer and purification.
How do you calculate theoretical yield?
Balance the chemical equation, convert the known reactant amount to moles, identify the limiting reactant if more than one reactant amount is given, use the mole ratio to calculate product moles, then multiply by product molar mass if the answer should be in grams.
What is the theoretical yield formula?
For a one-reactant mass-to-mass problem: theoretical yield = reactant mass ÷ reactant molar mass × product coefficient ÷ reactant coefficient × product molar mass. The coefficient ratio must come from the balanced equation.
How do you calculate theoretical yield in grams?
After the mole-ratio step gives product moles, multiply by the product molar mass in g/mol. For example, 1.984 mol H₂O × 18.015 g/mol = 35.74 g H₂O.
How do you calculate theoretical yield from a limiting reactant?
Convert each supplied reactant amount to moles and divide by its balanced coefficient. The smallest moles ÷ coefficient value is the limiting reactant. Use that reactant's available reaction extent to calculate product moles and final theoretical yield.
What is the difference between theoretical yield and actual yield?
Theoretical yield is the maximum product predicted by the balanced equation. Actual yield is the amount of product actually collected in an experiment. Percent yield compares them: actual yield ÷ theoretical yield × 100%.
Can theoretical yield be greater than actual yield?
Yes. Theoretical yield is usually greater than actual yield because it assumes an ideal reaction with no side reactions, no equilibrium loss, no incomplete conversion, and no product lost during collection.