🧯 Stoichiometry Calculator
Enter a reaction and the masses of your reactants — the tool balances it, finds the limiting reagent, and computes the theoretical yield of each product.
Balanced: N2 + 3H2 → 2NH3
Reactant amounts (grams) — enter one or more
Limiting reagent
N2
| Species | Moles | Mass (g) | Role |
|---|---|---|---|
| N2 | 0.9995 | 28 | limiting — fully consumed |
| 3H2 | 2.9985 | 6.045 | 3.955 g left over |
| 2NH3 | 1.999 | 34.045 | produced |
Masses shown are theoretical (100% yield). For actual yield, use the percent-yield calculator.
Balances the equation, finds the limiting reagent (min moles ÷ coefficient), and computes theoretical yield. 🔒 In your browser.
How the stoichiometry calculator works
The equation is balanced exactly (integer coefficients from the reaction’s null-space). For each reactant you supply a mass, the tool converts to moles (mass ÷ molar mass) and divides by the coefficient; the smallest of these ratios is the extent of reaction, and the reactant that produces it is the limiting reagent. Every species’ produced amount is coefficient × extent, converted back to mass; leftover reactant is what remains.
This composes the two exact cores — the equation balancer and the molar-mass parser. Finding the limiting reagent and theoretical yield is precisely where chatbots slip; here it is deterministic, with the moles and masses laid out.
Frequently asked questions
How do I do a stoichiometry calculation?
Write the reaction and enter the masses of the reactants you have. The tool balances the equation, converts masses to moles, finds the limiting reagent, and gives the theoretical mass of each product — the standard mole-ratio method, done exactly.
How is the limiting reagent found?
For each reactant, divide its moles by its coefficient in the balanced equation. The smallest result is the limiting reagent — it runs out first and sets how much product can form.
What is theoretical yield?
The maximum product obtainable if the reaction goes to completion with no losses, based on the limiting reagent. The tool reports it in grams and moles for every product.
Does it show leftover reactant?
Yes — for reactants in excess it shows how much remains after the limiting reagent is consumed.
Do I have to balance the equation first?
No — the tool balances it for you, then does the stoichiometry on the balanced form.
How do I get actual yield?
Multiply the theoretical yield by your percent yield, or use the percent-yield calculator with your measured actual yield.