# Limiting Reagent Calculator

Free limiting reagent calculator. Determine which reactant limits the reaction, excess remaining, and theoretical yield. Step-by-step solution.

## What this calculates

Find the limiting reagent in a chemical reaction. Enter the moles and stoichiometric coefficients of two reactants to determine which runs out first, how much excess remains, and the theoretical yield of product.

## Inputs

- **Moles of Reactant A** (mol) — min 0 — Amount of reactant A in moles.
- **Coefficient of A** — min 1, max 20 — Stoichiometric coefficient of A in the balanced equation.
- **Moles of Reactant B** (mol) — min 0 — Amount of reactant B in moles.
- **Coefficient of B** — min 1, max 20 — Stoichiometric coefficient of B in the balanced equation.
- **Coefficient of Product** — min 1, max 20 — Stoichiometric coefficient of the product.
- **Product Molar Mass** (g/mol) — min 0 — Enter to calculate theoretical yield in grams.

## Outputs

- **Limiting Reagent** — formatted as text — Which reactant is the limiting reagent.
- **Excess Reagent** — formatted as text — Which reactant is in excess.
- **Excess Moles Remaining** (mol) — Moles of excess reagent remaining after reaction.
- **Product (moles)** (mol) — Moles of product formed (theoretical).
- **Product (grams)** — formatted as text — Grams of product formed (if molar mass provided).
- **Calculation** — formatted as text — Step-by-step determination.

## Frequently Asked Questions

**Q: What is a limiting reagent?**

A: The limiting reagent is the reactant that is completely consumed first in a reaction, determining the maximum amount of product that can form. The other reactant(s) are in excess.

**Q: How do I find the limiting reagent?**

A: Divide the moles of each reactant by its stoichiometric coefficient. The reactant with the smallest ratio is the limiting reagent.

**Q: What happens to the excess reagent?**

A: The excess reagent is not completely consumed. Some of it remains unreacted after all the limiting reagent is used up. The amount remaining equals the initial amount minus what was consumed.

**Q: Why is identifying the limiting reagent important?**

A: The limiting reagent determines the theoretical yield (maximum product possible). Using the wrong reactant to calculate yield will give an incorrect answer. In industry, limiting reagents affect cost and waste.

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Source: https://vastcalc.com/calculators/chemistry/limiting-reagent
Category: Chemistry
Last updated: 2026-04-21