What is the limiting reagent?

The limiting reagent (or limiting reactant) is the reactant that is completely consumed first during a chemical reaction. It limits how much product can be formed. The reagent present in excess beyond the stoichiometric ratio is called the excess reagent.

How is theoretical yield calculated?

Theoretical yield is calculated by dividing the available moles of the limiting reagent by its stoichiometric coefficient, then multiplying by the product's coefficient, and finally multiplying by the product's molar mass to convert to grams.

Do I need to enter molar masses manually?

Yes — enter the molar mass (g/mol) for each species. You can find molar masses using a periodic table or a molar mass calculator. This design keeps the tool universal for any compound.

Can I enter amounts in moles instead of grams?

Yes. Toggle the unit selector to "mol" for any reactant and enter the mole amount directly. The calculator handles mixed units across reactants.

What if two reactants give the same limiting ratio?

Both are co-limiting reagents — the tool will flag the first one found. In practice, even a tiny difference in real amounts breaks the tie.

Does this work for reactions with more than two reactants?

Yes, you can add up to four reactants. The same limiting-reagent logic applies: the reactant with the smallest moles-divided-by-coefficient value limits the reaction.

Stoichiometry Calculator

Enter reactant coefficients and amounts to find the limiting reagent, excess reagent, and theoretical yield of any product.

Reactants

Target Product

Name (optional)

Coefficient

Molar Mass (g/mol)

Quick Examples

Enter reactants and product, then click Calculate

Mole Ratio Analysis

Reactant	Avail. (mol)	Coeff.	Ratio	Role

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Summary

Stoichiometry relates the quantitative amounts of reactants and products in a balanced chemical equation. This calculator accepts up to four reactants and one target product, each with their stoichiometric coefficients, molar masses, and available amounts. It converts masses to moles, applies the mole ratio from the balanced equation, identifies the limiting reagent, and computes the theoretical yield of the chosen product in both moles and grams.

How it works

Enter the stoichiometric coefficient and molar mass for each reactant.
Enter the available amount (grams or moles) of each reactant.
Enter the coefficient and molar mass of the product you want to find the yield for.
Click Calculate to convert all reactant amounts to moles.
The calculator divides each mole amount by its coefficient to get the mole ratio.
The reactant with the smallest mole ratio is the limiting reagent; the theoretical yield is calculated from it.

Use cases

Determine which reactant runs out first in a chemical reaction.
Calculate the theoretical yield of a product before running a lab experiment.
Find how much excess reagent remains after the reaction completes.
Convert between grams and moles using stoichiometric ratios.
Verify textbook stoichiometry problems step by step.
Plan reagent quantities for synthesis reactions in organic chemistry.
Teach limiting reagent concepts with an interactive visual aid.
Check percent yield by comparing actual yield to theoretical yield.

Frequently Asked Questions

Last updated: 2026-05-23 · Reviewed by Nham Vu