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Walk-through

How to Use This Calculator

3 steps

1

Enter the reactant mass, molar masses, and coefficients

On the Theoretical Yield tab, enter the mass of the limiting reactant in grams, its molar mass, and both the reactant's and the product's coefficients from the balanced chemical equation. Then enter the product's molar mass. The result updates live as you type.

2

Read the theoretical yield

The result card shows theoretical yield in grams — the maximum mass of product a perfectly efficient reaction could produce from that limiting reactant — plus the moles of product it corresponds to. The interpretation line restates it as "Max X g of product from Y g reactant."

3

Optionally estimate actual yield, or convert moles

Switch to the With % Yield tab and enter a percent yield to estimate the real-world actual yield from the theoretical maximum you just calculated. Or switch to the Mole Ratio tab for a standalone mol-to-mol conversion using the same balanced-equation coefficients, without needing any mass at all.

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Reference

Formula & Methodology

2 formulas

Theoretical yield (mole chain)

moles reactant = mass ÷ molar mass → moles product = moles reactant × (coeff product ÷ coeff reactant) → theoretical yield = moles product × product molar mass

Theoretical yield is found in three steps: convert the limiting reactant's mass to moles using its molar mass, convert moles of reactant to moles of product using the mole ratio from the balanced equation's coefficients, then convert moles of product back to mass using the product's molar mass.

Actual yield from percent yield

actual yield = theoretical yield × (percent yield ÷ 100)

If a reaction historically runs at a known percent yield, multiplying the theoretical yield by that percentage estimates the real-world actual yield you can expect to recover.

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Glossary

Key Terms Explained

6 terms

Theoretical yield The maximum possible mass of product a reaction can form from the limiting reactant, assuming complete conversion with no losses — the ceiling stoichiometry predicts.

Limiting reactant The reactant that runs out first in a chemical reaction, capping how much product can form regardless of how much of the other reactants remain unreacted.

Mole ratio The ratio between the coefficients of two species in a balanced chemical equation, used to convert moles of one substance to moles of another.

Actual yield The mass of product actually recovered and measured after running a real reaction, always less than or equal to the theoretical yield in a clean reaction.

Percent yield Actual yield divided by theoretical yield, expressed as a percentage — a measure of how efficiently a reaction converted the limiting reactant into product.

Molar mass The mass in grams of one mole of a substance, used to convert between the mass of a chemical and the number of moles it represents.

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Scenarios

Real-World Examples

3 worked examples

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Basic 1:1 reaction

5 g of a 40 g/mol reactant, 1:1 mole ratio

Reactant mass 5 g Reactant molar mass 40 g/mol Coefficients 1 : 1 Product molar mass 58.44 g/mol

5 g ÷ 40 g/mol = 0.125 mol reactant. At a 1:1 ratio that's 0.125 mol product, and 0.125 mol × 58.44 g/mol = 7.31 g theoretical yield — the most product this reaction could possibly form.

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Predicting actual yield

Same reaction, but the lab typically runs at 80% yield

Theoretical yield 7.31 g Percent yield 80%

Actual yield = 7.31 g × 0.80 ≈ 5.84 g. A chemist who knows this reaction usually runs at 80% efficiency can predict roughly 5.84 g of recoverable product before ever running it.

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Mole-to-mole only

0.5 mol of a species with coefficient 2, converting to a species with coefficient 3

Moles you have 0.5 mol Coefficients 2 → 3

0.5 mol × (3 ÷ 2) = 0.75 mol of the other species — a mole-ratio conversion with no mass or molar mass required at all.

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Deep Dive

Understanding Theoretical Yield

3 chapters · 4 min read

Theoretical yield is the most product a chemical reaction could ever produce, calculated from the limiting reactant using stoichiometry. It's the benchmark every real-world reaction is measured against, and it's the starting point for calculating percent yield.

How theoretical yield works

Theoretical yield comes from a three-step mole chain. First, convert the mass of the limiting reactant — the reagent that runs out first — into moles by dividing by its molar mass. Second, use the mole ratio from the balanced chemical equation's coefficients to convert moles of reactant into moles of product: multiply by (coefficient of product ÷ coefficient of reactant). Third, convert moles of product back into mass by multiplying by the product's molar mass.

This calculation assumes perfect, complete conversion of the limiting reactant with zero losses — a reaction never quite achieves in practice, which is exactly why percent yield exists as a separate measure of real-world efficiency.

Inputs and what they mean

Reactant mass and reactant molar mass together determine how many moles of the limiting reactant you're starting with. The coefficients come directly from the balanced chemical equation — get these wrong and every downstream number is wrong, since the mole ratio is the entire bridge between reactant and product. Product molar mass converts the final mole count back into a mass you can actually weigh on a balance.

On the With % Yield tab, entering a percent yield (from a lab manual, historical data, or a prior run of the same reaction) scales the theoretical yield down to a realistic actual-yield estimate. The Mole Ratio tab strips away mass entirely, letting you convert directly between moles of any two species in the equation using just their coefficients.

Limits and edge cases

This calculator assumes you've already correctly identified the limiting reactant — if you have amounts of two reactants and aren't sure which one runs out first, use a limiting-reagent calculator before this one. Theoretical yield also assumes the balanced equation and its coefficients are correct; a common mistake is entering coefficients from an unbalanced or partially balanced equation.

A theoretical yield calculation says nothing about how a reaction will actually perform in the lab — side reactions, incomplete conversion, and purification losses are all outside its scope. That's the job of percent yield, calculated separately once you have both the theoretical yield from this tool and a measured actual yield from the lab.

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Questions

Frequently Asked Questions

6 questions

What is theoretical yield?+

Theoretical yield is the maximum possible mass of product a chemical reaction could form, calculated from the limiting reactant assuming the reaction goes to completion with no losses.

What is theoretical yield calculated from?+

It's calculated from the limiting reactant — the reagent that runs out first — using its mass, its molar mass, the balanced-equation mole ratio, and the product's molar mass.

What's the difference between actual and theoretical yield?+

Theoretical yield is the ideal maximum predicted by stoichiometry. Actual yield is what you really measure and recover in the lab, which is almost always lower due to side reactions, incomplete conversion, and losses during purification.

Can I combine theoretical yield with a percent yield?+

Yes — multiply the theoretical yield by the percent yield (divided by 100) to estimate the actual yield a reaction with that known efficiency would produce. Use the With % Yield tab to do this automatically.

What units does the calculator expect?+

Reactant mass and product mass are in grams (g). Molar masses are in grams per mole (g/mol). Coefficients are unitless whole numbers from the balanced equation.

Where does the mole ratio come from?+

The mole ratio comes directly from the coefficients in front of each species in the balanced chemical equation — for example, in 2 A + B → 3 C, the mole ratio of A to C is 2:3.

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Theoretical Yield Calculator

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