Limiting Reagent & Stoichiometry Calculator
Type any reaction, enter grams of each reactant and find the limiting reagent and yield.
Drag the reactant bars up or down to change how many grams you have, or type the numbers in the table.
| Substance | Molar mass | Start (g) | Moles | Moles ÷ coefficient | Left over (g) | Made (g) |
|---|
About the Limiting Reagent & Stoichiometry Calculator
Free stoichiometry and limiting reagent calculator. Type your own reaction, enter the mass of each reactant, and see moles, the limiting reagent, theoretical yield and leftover excess, with a percent-yield check. Built for chemistry, the limiting reagent & stoichiometry calculator runs instantly in your browser: change a setting or drag an object and the result updates at once, so you learn by trying things out rather than only reading about them.
Type any reaction, enter grams of each reactant and find the limiting reagent and yield. Use it to explore chemistry ideas at your own pace, then check what you found against the key ideas further down this page.
How to use the Limiting Reagent & Stoichiometry Calculator
- Use the controls to change Type a reaction (balancing is automatic), Actual yield of the first product (g). The simulation reacts instantly.
- Press "Calculate" to start, reset or change what is happening.
- Where you see a glowing handle, object, weight or atom, drag it with your mouse or finger. Everything responds in real time.
- Watch the readouts and graphs update as you experiment, and compare what you see with the key ideas below.
Things to try
- Load the ammonia reaction and give it 10 g of N₂ and 10 g of H₂.
- Type your own reaction, for example Al + Fe2O3 -> Al2O3 + Fe.
- Change the grams and watch the limiting reagent switch.
- Enter an actual yield and read the percent yield.
Key ideas you can learn
- The limiting reagent is the reactant that runs out first and decides how much product you can make.
- Convert grams to moles, then divide by the coefficient to compare reactants fairly.
- Percent yield = actual yield ÷ theoretical yield × 100.
Where this is used in the real world
Chemical plants, pharmaceutical labs and food manufacturers all calculate limiting reagents so they do not waste expensive chemicals. It is also a core skill in every chemistry exam.
Who is this simulation for?
Chemistry students from middle school to university, teachers who need a virtual demonstration, and anyone without access to a lab. It is safe, free and repeatable as many times as you like.
For teachers: project it on the board, let students predict what will happen, then run it together. For students: change one thing at a time and write down what changes.
Frequently asked questions
How do you find the limiting reagent?
Convert each reactant to moles and divide by its coefficient in the balanced equation. The smallest result is the limiting reagent.
What is theoretical yield?
The maximum amount of product you could make if the reaction went perfectly, calculated from the limiting reagent.
Is the Limiting Reagent & Stoichiometry Calculator free to use?
Yes. It is completely free, with no signup, no download and no ads inside the simulation. It runs in your web browser.
Does the Limiting Reagent & Stoichiometry Calculator work on a phone or tablet?
Yes. It uses touch as well as the mouse, so you can drag objects with your finger. A larger screen makes the controls easier to see.