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Stoichiometry Calculator

Turn reactant masses into moles, limiting reagent and product masses for balanced reactions.

Reactant and product amounts

Limiting reagent: —
Extent of reaction: —
Moles come from the balanced coefficients and are converted to grams with standard molar masses.

How to use the Stoichiometry Calculator

  1. Choose one of the balanced reactions from the list.
  2. Enter the mass of the first reactant and, if used, the second.
  3. Read the limiting reagent plus the moles and grams of every species.

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Frequently Asked Questions

Common questions about the free online stoichiometry calculator.

Stoichiometry uses the mole ratios from a balanced equation to work out how much of each reactant is used and how much product forms.
Convert each reactant mass to moles, divide by its coefficient in the equation, and the smallest of those results comes from the limiting reagent.
It is the number of times the balanced equation runs. Multiply it by each coefficient to get the moles of every reactant and product.
Multiply the moles by the molar mass of the substance. One mole of water has a mass of about 18.015 grams.
The molar mass of hydrogen gas is about 2.016 g/mol, so exactly one mole of H2 has a mass of 2.016 grams rather than 2 grams.
Eight common balanced reactions are built in, including hydrogen burning, ammonia synthesis, methane combustion and limestone decomposition.
No. Everything is calculated in your browser, so the values you enter stay on your own device.
Yes. The calculator is responsive and works on phones, tablets and desktop browsers with no installation.

Last updated: October 10, 2026