Molar Ratio Calculator

Chemical Stoichiometry & Reaction Balance

A Molar Ratio derives directly from the coefficients of a balanced chemical equation, establishing the mole-to-mole conversion factors between reactants and products.

Core Stoichiometric Equations

• Molar Ratio: R_B/A = Coefficient_BCoefficient_A

• Theoretical Product Moles: n_B = n_A · (Coefficient_BCoefficient_A)

• Stoichiometric Fraction (X_A): X_A = Coefficient_ACoefficient_A + Coefficient_B

• Percentage Yield: \% Yield = Actual YieldTheoretical Yield × 100\%

Classic Haber Process Ammonia Example

Balanced Equation: N_2 + 3H_2 2NH_3

• Molar ratio of H_2 to N_2 is 3 :

1.

• Molar ratio of NH_3 to H_2 is 2 :

3.

• Reacting 6.0 moles of H_2 yields 6.0 × (2) / (3) = 4.0 moles of NH_

3.

Limiting Reagent Identification

In real laboratory syntheses where reactants are mixed in non-stoichiometric amounts, divide actual moles by equation coefficients to find the limiting reagent that stops the reaction.

Industrial Chemical Process Scaling

Chemical engineers scale benchtop beaker syntheses to 10,000-liter industrial reactors by applying exact stoichiometric molar ratios to calculate mass flow rates of raw feedstocks.

How to Use This Calculator

Enter your Stoichiometric Coefficient A (e.g. 2 in coeff), Actual Moles Reactant A (e.g. 4.0 in mol), and Stoichiometric Coefficient B (e.g. 2 in coeff). Results update instantly as you type — adjust any value to compare scenarios.

The Formula

Formula Reference: Molar Ratio Calculator

Input variables:

coeffReactantA — Stoichiometric Coefficient A

molesReactantA — Actual Moles Reactant A

coeffProductB — Stoichiometric Coefficient B

Computed outputs:

theoreticalMolesProductB — Theoretical Moles Product B

molarRatioAB — Molar Ratio (B : A)

moleFractionA — Stoichiometric Fraction A

moleFractionB — Stoichiometric Fraction B

Mathematical relationships extracted from calculation logic:

molesB = molesA * ratio

totalCoeff = coeffA + coeffB

Standard: NIST / ISO mathematical definitions

Worked Example

Calculating product yield for 4.00 moles of Reactant A with a 2:2 stoichiometric equation ratio: Yields 4.0000 theoretical moles of Product B (1.0000 molar ratio B:A).

Understanding Your Result

Percentages are relative values — context determines what is "good" or "bad." A 50% discount is significant; a 50% failure rate is alarming. Percentage change and percentage points are different: moving from 4% to 5% is a 1 percentage point increase, but a 25% relative increase. When comparing percentages across different base values, always check whether absolute differences are meaningful — a 10% improvement on a large base creates more absolute value than 10% on a small base.