Molar Ratio Calculator

All chemistry tools

Calculate the molar ratio between two chemical species from stoichiometric coefficients or moles.

Stoichiometry

Moles/Coefficient A

Moles/Coefficient B

Ratio Analysis

Enter coefficients or moles to calculate ratio

About this calculator

Overview

Molar ratios express the relative amounts of substances in a chemical reaction, derived directly from the coefficients in a balanced chemical equation. These ratios are fundamental to stoichiometry, allowing chemists to predict how much product forms from given reactants and to identify limiting reagents. They represent the precise 'recipe' for chemical transformations.

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Pro Tips

Ratio = moles_A / moles_B from balanced equation coefficients.
To find moles of one substance: moles_X = moles_known × (coeff_X / coeff_known).
Always balance the chemical equation first before calculating ratios!
Molar ratios are dimensionless—they don't depend on whether you use moles or 'molecules'.
Use these ratios to determine which reactant will run out first (the limiting reactant).

Fun Facts

"Molar ratios are why baking recipes are similar to chemical equations—precise proportions are key!"
"They explain why rocket fuel mixtures (like liquid hydrogen and oxygen) must be perfectly balanced for lift-off."
"The Law of Definite Proportions (Proust, 1799) states compounds have fixed mass ratios, which are governed by these molar ratios."
"In the Haber process for creating ammonia, the N₂:H₂ molar ratio is exactly 1:3."
"Automobile engines use an air-to-fuel molar ratio to regulate emissions and fuel economy."
"Molar ratios can tell you if a reaction is 'stoichiometrically balanced' or if one reactant is in excess."
"The ratios are derived from the 'stoichiometric coefficients'—the numbers in front of chemical formulas in an equation."
"If you double the moles of one reactant, the molar ratio relative to others changes unless you adjust them accordingly."

Formula: Molar Ratio = n(A) / n(B)