Read a mole ratio from a balanced equation
A molar ratio calculator turns balanced coefficients into a clearly directed relationship between two species. Enter each unique species with its positive whole-number coefficient, then name the starting and compared species. The page reports both the coefficient ratio and the amount corresponding to the entered starting moles, so “product per reactant” cannot be confused with its reciprocal.
Mole ratios are the bridge between a balanced equation and stoichiometric calculations. They apply to amounts in moles, formula units, molecules, or another consistent particle count basis. The calculator does not balance the equation or infer which row represents a limiting reactant. Use coefficients only after checking conservation, and keep species names identical between the row list and the two selection fields.
Use coefficients as conversion factors
If the balanced equation is aA + bB → cC, then c moles of C correspond stoichiometrically to a moles of A. To convert an A amount to C, multiply by c/a. Reversing direction uses a/c. The units cancel like an ordinary conversion factor: mol A × (c mol C ÷ a mol A) leaves mol C.
Coefficients must be positive whole numbers from one balanced equation. Scaling the entire equation by the same factor does not change any ratio because numerator and denominator scale together. The tool rejects duplicate species and same-species comparisons, which would obscure the intended direction. It also shows the reverse ratio as a quick reminder that direction changes the numerical multiplier.
Follow a molar ratio example
For N2 + 3H2 → 2NH3, the NH3-per-N2 ratio is 2:1. Starting with 1.5 mol N2 corresponds to 1.5 × 2/1 = 3.0 mol NH3 on the ideal stoichiometric basis. The H2-per-N2 ratio is 3:1, so the same 1.5 mol N2 would require 4.5 mol H2 for exact stoichiometric consumption.
If you instead ask for N2 per NH3, the ratio is 1:2 and 3.0 mol NH3 corresponds to 1.5 mol N2. Writing the species beside both numbers prevents a common error where a correct pair of coefficients is applied backward. Keep unrounded coefficients and amounts during the calculation; round only the final amount according to the source data.
Move from a mole ratio to a real stoichiometry problem
A reaction with several reactants must first compare each available amount with its coefficient to identify the limiting reactant. The selected ratio then gives the theoretical product from that limiting basis. Excess reactants remain after the limiting reactant is consumed. A ratio alone cannot tell which input limits the reaction because it contains no information about amounts actually available.
Mass values must be converted to moles before applying a mole ratio, using the molar mass of the exact chemical form. After calculating product moles, convert back to mass if required. Actual recovery can be lower because of incomplete conversion, equilibrium, side reactions, purification losses, or measurement uncertainty; those effects belong in yield analysis rather than the balanced coefficient ratio.
Stoichiometric scope, laboratory limits, and privacy
Balanced coefficients express theoretical proportions, not a safe recipe or proof of reaction performance. Real procedures may add one reagent in excess, use a catalyst or solvent, control addition rate, or require hazard-specific containment. Follow an authoritative method and qualified chemical safety guidance before turning a classroom ratio into quantities for a real experiment or process.
The values are calculated in the current browser tab. NexaCurrent does not upload the quantities, formulas, chemical names, element choices, or other information entered here, and no account is needed. Copying is a deliberate action after the answer and working are visible. Refreshing or leaving the page clears the current calculation, so keep a copied result if it is needed for later study.