๐งชLimiting Reagent Calculator
Enter a balanced chemical equation and the amount of each reactant to find the limiting reagent, theoretical yield, and leftover excess.
Free Limiting Reagent Calculator
Not sure which reactant runs out first? Our free Limiting Reagent Calculator finds the answer instantly. Enter a balanced chemical equation and the amount of each reactant you have โ in grams or moles โ and it converts everything to moles, compares against the stoichiometric ratios, and identifies exactly which reactant limits the reaction.
From there it calculates the theoretical yield of your chosen product and tells you how much of each excess reactant is left over once the reaction is complete. Every step of the mole-ratio comparison and yield calculation is shown, so you can follow the reasoning rather than just seeing a final number.
Built for stoichiometry homework and lab prep, it runs entirely in your browser โ no sign-up, no downloads, and no limits on how many reactions you check. See the About page or the FAQ for more.
About the Limiting Reagent Calculator
Features
Equation parsing
Enter any balanced equation with any number of reactants and products.
Grams or moles per reactant
Each reactant has its own unit toggle, with molar mass computed automatically.
Mole-ratio comparison table
See every reactant's moles-divided-by-coefficient value side by side.
Theoretical yield & excess
Full working for the product yield and how much of each other reactant is left over.
Frequently Asked Questions
How does the limiting reagent calculator work?
Enter a balanced equation and the amount of each reactant; it converts to moles, compares against stoichiometric ratios, and identifies the limiting reactant.
Is it free?
Completely free, no sign-up, downloads, or limits.
Can I enter amounts in grams instead of moles?
Yes, each reactant has its own grams/moles toggle; molar mass is calculated automatically from the formula.
Does it work with more than two reactants?
Yes, any number of reactants in the equation are compared.
What if my equation isn't balanced?
It's flagged clearly rather than silently computed wrong; balance it first with a chemical equation balancer.
Does it calculate theoretical yield?
Yes, for your chosen product, based on the limiting reactant's available moles.
Does it show how much excess reagent is left?
Yes, for every non-limiting reactant, in both grams and moles.
Does it show the steps?
Yes, the full mole conversion and comparison table is shown, not just the final answer.
Is my data stored?
No; everything runs in your browser and isn't stored or sent anywhere.
Does it work on mobile?
Yes, fully responsive on all screen sizes.