Stoichiometry Calculator Online

Calculate limiting reactants, theoretical yield, percent yield & mass conversions

⚖️ Limiting Reactant Calculator

Balanced Equation (e.g., 2H2 + O2 → 2H2O)

Reactant A (name)

Molar Mass A (g/mol)

Amount of A

Coefficient of A

Reactant B (name)

Molar Mass B (g/mol)

Amount of B

Coefficient of B

📐 Key Stoichiometry Formulas

Moles = Mass (g) / Molar Mass (g/mol)

Mass = Moles × Molar Mass

Percent Yield = (Actual / Theoretical) × 100%

Mole Ratio: n₁/coef₁ = n₂/coef₂

Limiting Reactant: smallest (moles / coefficient)

Stoichiometry Calculator Online - Complete Guide

This stoichiometry calculator online helps you solve chemical reaction problems including limiting reactants, theoretical yield, percent yield, and mass-mole conversions.

What is Stoichiometry?

Stoichiometry is the calculation of reactants and products in chemical reactions using balanced equations. It's based on the law of conservation of mass.

How to Find the Limiting Reactant

Convert all reactant amounts to moles
Divide moles by the coefficient in the balanced equation
The reactant with the smallest ratio is the limiting reactant
The other reactant(s) are in excess

Calculating Theoretical Yield

Identify the limiting reactant
Use mole ratios from the balanced equation
Convert moles of product to grams using molar mass

Understanding Percent Yield

Percent yield compares what you actually obtained to the theoretical maximum:

100% = Perfect efficiency (rarely achieved)
>100% = Error or impurities present
<100% = Normal due to losses, side reactions

Common Molar Masses

H₂O: 18.015 g/mol
CO₂: 44.01 g/mol
NaCl: 58.44 g/mol
H₂SO₄: 98.079 g/mol
NaOH: 40.00 g/mol

Frequently Asked Questions

What is the limiting reactant?

The limiting reactant is the substance that is completely consumed first in a reaction, limiting the amount of product that can form. The other reactants are "in excess."

How do I calculate theoretical yield?

Theoretical yield is calculated from the limiting reactant using mole ratios. Multiply moles of limiting reactant by the mole ratio, then convert to grams using the product's molar mass.

Why is my percent yield over 100%?

A percent yield over 100% usually indicates experimental error, impurities in the product, incomplete drying, or measurement mistakes. Pure products cannot exceed 100% yield.

How do I balance a chemical equation?

Balance equations by adjusting coefficients so atoms of each element are equal on both sides. Start with the most complex molecule and balance one element at a time.

Is this stoichiometry calculator online free?

Yes! This stoichiometry calculator is completely free with no limitations or sign-up required.