ChemBench

Theoretical Yield Calculator

The best-case output of a reaction.

Limiting reactant moles

Reactant coefficient

Product coefficient

Product molar mass (g/mol)

Theoretical yield

36 g

What you entered

Limiting reactant moles: 2Reactant coefficient: 1Product coefficient: 1Product molar mass (g/mol): 18

1
Moles of product = (limiting moles ÷ reactant coeff) × product coeff
(2 ÷ 1) × 1= 2
2
Theoretical yield = moles × molar mass
2 × 18= 36 g

Result

Theoretical yield: 36 g

The maximum possible yield from this reaction is 36g of product.

Theoretical yield from the limiting reactant

Scale the limiting reactant's moles by the product-to-reactant coefficient ratio, then multiply by the product's molar mass.

Limiting moles	Reactant coeff.	Product coeff.	Product molar mass	Theoretical yield
2 mol	1	1	18.015 g/mol	36.030 g
2 mol	2	1	44.01 g/mol	44.010 g
0.5 mol	1	2	58.44 g/mol	58.440 g
1.5 mol	3	2	17.031 g/mol	17.031 g
3 mol	1	1	180.156 g/mol	540.468 g

The coefficient ratio is what people skip. In row two, two moles of reactant give only one mole of product, so the yield is half what a straight mole-for-mole assumption predicts.

Stoichiometric ratio times molar mass

Theoretical yield converts the limiting reactant's moles into moles of product (using the balanced equation's coefficient ratio), then multiplies by the product's molar mass to get an answer in grams.

The upper bound every real yield is measured against

No real reaction exceeds its theoretical yield — it's the benchmark used to calculate percent yield and judge how efficient an actual lab or industrial run was.

Frequently asked questions

If I have 5.0 mol of limiting reactant and the product ratio is 1:1 with a product molar mass of 58.44 g/mol, what is the theoretical yield?

Theoretical yield = 5.0 mol × (1/1) × 58.44 g/mol = 292.2 g. That is the maximum you could collect under perfect conditions.

How does theoretical yield connect to percent yield?

Theoretical yield is the denominator in the percent yield formula: % yield = (actual yield / theoretical yield) × 100. Calculate theoretical yield here first, then use the percent yield calculator with your actual lab result.

Why is my actual yield always less than the theoretical yield?

Side reactions consume some reactant, product is lost during filtration or transfer, and some reactions simply do not go to completion. Industrial processes typically optimize for 80-95% of theoretical yield.