Enter a balanced chemical equation and instantly get the mole ratio for every reactant and product.Visualize stoichiometric proportions with an interactive bar chart.
In chemistry, the mole ratio (or stoichiometric ratio) is the ratio of the amounts in moles of any two substances involved in a chemical reaction. It is derived directly from the balanced chemical equation — the coefficients in front of each chemical formula indicate the relative number of moles of each reactant consumed and each product formed.
For the general reaction aA + bB → cC + dD
the mole ratio of A to B is a : b, of A to C is a : c, and of C to D is c : d.
Mole ratios are the foundation of stoichiometry — the branch of chemistry that deals with the quantitative relationships between reactants and products. They enable chemists to predict how much product will form from a given amount of reactant, how much of a reactant is needed to completely consume another, and which reactant is the limiting reagent.
Our mole ratio calculator uses a symbolic parser to analyse your input chemical equation. It splits the equation into reactants and products, identifies each substance, and extracts its stoichiometric coefficient. The coefficients are then normalised to the simplest whole‑number ratio by dividing by the greatest common divisor (GCD) of all coefficients.
For example, the equation 2H₂ + O₂ → 2H₂O yields coefficients [2, 1, 2]. The GCD is 1, so the mole ratio is displayed as 2 : 1 : 2. If the equation were 4Fe + 3O₂ → 2Fe₂O₃, the GCD is 1, but if all coefficients share a common factor, the calculator reduces them automatically.
A critical prerequisite for any mole‑ratio calculation is that the input equation must satisfy the law of conservation of mass—each element must have the same number of atoms on both sides. While this tool does not automatically balance equations (as that would involve solving a system of linear Diophantine equations), it is designed to work with balanced inputs. Users are strongly advised to verify atom counts before relying on the output for quantitative lab work. For quick verification, check that the sum of atomic masses on each side is equal.
The interactive bar chart visualises each substance's coefficient, making it easy to compare the relative amounts at a glance. Reactants are shown in teal with diagonal stripes, products in orange with opposite‑diagonal stripes — the patterns ensure accessibility for colour‑blind users.
All calculations are performed locally; no data is transmitted. The tool supports a wide range of chemical formulas, including those with subscripts (e.g. H₂O, CO₂, C₆H₁₂O₆) and single‑level parentheses (e.g. Ca(OH)₂, (NH₄)₂SO₄) as long as they are written without spaces within the formula.
The table below lists common reactions with their balanced equations, coefficients, and mole ratios. All examples have been verified against standard chemistry references (Chang, R. "Chemistry"; Atkins, P. "Physical Chemistry").
| Reaction | Balanced Equation | Coefficients | Mole Ratio (simplified) |
|---|---|---|---|
| Water synthesis | 2H₂ + O₂ → 2H₂O | 2, 1, 2 | 2 : 1 : 2 |
| Haber process | N₂ + 3H₂ → 2NH₃ | 1, 3, 2 | 1 : 3 : 2 |
| Methane combustion | CH₄ + 2O₂ → CO₂ + 2H₂O | 1, 2, 1, 2 | 1 : 2 : 1 : 2 |
| Decomposition of KClO₃ | 2KClO₃ → 2KCl + 3O₂ | 2, 2, 3 | 2 : 2 : 3 |
| Neutralisation | HCl + NaOH → NaCl + H₂O | 1, 1, 1, 1 | 1 : 1 : 1 : 1 |
| Photosynthesis | 6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂ | 6, 6, 1, 6 | 6 : 6 : 1 : 6 |
The Haber process synthesises ammonia (NH₃) from nitrogen (N₂) and hydrogen (H₂) :
N₂ + 3H₂ → 2NH₃
The mole ratio of N₂ : H₂ : NH₃ is 1 : 3 : 2. This means that for every 1 mole of N₂ consumed, 3 moles of H₂ are required and 2 moles of NH₃ are produced.
Suppose an industrial reactor is charged with 50.0 mol of N₂ and 150.0 mol of H₂. The stoichiometric ratio requires exactly 3 mol of H₂ per 1 mol of N₂. With 50 mol N₂, the required H₂ is 50 × 3 = 150 mol — perfectly matched. The theoretical yield of NH₃ is 50 × 2 = 100 mol. If the actual yield is 92 mol, the percent yield is 92 %.
This calculator gives you the mole ratio instantly, so you can quickly perform such stoichiometric calculations. For mass‑based problems, multiply the mole ratio by the molar masses of the substances involved.
In thermochemistry, mole ratios are used to calculate enthalpy changes (ΔH) per mole of reaction. For example, the combustion of methane releases 890 kJ per mole of CH₄ — the mole ratio between CH₄ and energy is 1 : 890 kJ.
In kinetics, the rate of a reaction is often expressed in terms of the change in concentration of a reactant or product, divided by its stoichiometric coefficient. The mole ratio ensures that the rate is the same regardless of which substance is monitored.
In electrochemistry, mole ratios relate the amount of substance consumed or produced at an electrode to the quantity of electric charge passed (Faraday's laws). For example, the reduction of Cu²⁺ to Cu requires 2 mol of electrons per mole of Cu.
In green chemistry, mole ratios help calculate atom economy — the proportion of reactant atoms that end up in the desired product. A reaction with a high atom economy minimises waste, and the mole ratio is central to this calculation.