BYTETOOLS

Stoichiometry Calculator

Type a balanced equation, give the amount of one substance, and get moles and grams of every other reactant and product with the working shown.

0.081603
Moles of KClO₃
0.040801 mol
Extent of reaction
3
Species in equation

Theoretical amounts for every species

SpeciesCoeff.M (g/mol)MolesMass (g)
KClO₃reactant · given2122.5450.08160310
KClproduct274.5480.0816036.0833
O₂product331.9980.1224043.9167

Every row is 0.040801 mol of reaction × its coefficient. Mass = moles × molar mass.

Atom balance check

ElementReactant atomsProduct atomsMatch
Cl22yes
K22yes
O66yes

These are theoretical yields: they assume the reaction goes to completion and that every other reactant is present in excess. Real yields are lower — divide the mass you actually collect by the mass below to get a percent yield.

What is the Stoichiometry Calculator?

Stoichiometry converts an amount of one substance into amounts of everything else in a reaction. Convert the known amount to moles, divide by that species' coefficient to get the extent of reaction, then multiply by each other coefficient.

  • Parses coefficients, brackets, multi-letter symbols and hydrate dots
  • Known amount as mass, moles, or molarity multiplied by volume
  • Molar mass and theoretical yield for every reactant and product
  • Atom balance check that flags an unbalanced equation instead of hiding it
  • Extent-of-reaction figure so you can follow the arithmetic
  • Runs entirely in your browser — nothing is uploaded

How to use the Stoichiometry Calculator

  1. 1

    Type the balanced equation, using -> or = between the two sides and + between species.

  2. 2

    Choose which substance you know the amount of from the dropdown.

  3. 3

    Pick whether that amount is a mass in grams, a number of moles, or a molarity and volume.

  4. 4

    Read the moles and grams of every species in the results table.

  5. 5

    Check the atom balance panel to confirm the equation really is balanced, then copy the table.

About the Stoichiometry Calculator

The ByteTools Stoichiometry Calculator takes a balanced chemical equation and one known amount, then works out how much of every other species is involved. Enter something like 2 KClO3 -> 2 KCl + 3 O2, say you are starting with 10 grams of potassium chlorate, and the table underneath fills in moles and grams for the potassium chloride and oxygen too.

It is built for the limiting-reagent and theoretical-yield questions that fill a first-year chemistry course, and for anyone scaling a preparation up or down in a lab. The known amount can be a mass, a number of moles, or a concentration multiplied by a volume, so a solution-phase reaction needs no separate conversion step beforehand.

Molar masses come from a built-in table of IUPAC standard atomic weights and every calculation runs in JavaScript inside your browser. Nothing you type is uploaded or stored anywhere, so the page is instant, private, and keeps working after you go offline.

Frequently asked questions

How do you do stoichiometry step by step?

Convert the amount you know into moles, divide by that substance's coefficient to get the extent of the reaction, then multiply that figure by the coefficient of whatever you want to find. Multiplying the result by its molar mass turns it back into grams.

Does the equation have to be balanced first?

Yes, because the mole ratios come straight from the coefficients. This tool counts the atoms on each side and warns you when they do not match, so an unbalanced equation gives a visible warning rather than a quietly wrong answer.

What is theoretical yield and why is my real yield lower?

Theoretical yield is the mass you would get if the reaction ran to completion with no losses. Real reactions stop at equilibrium, run side reactions and lose product during transfer and purification, so actual yields are almost always lower. Divide the mass you collect by the theoretical yield for a percent yield.

How do I enter a reaction that happens in solution?

Set the given amount to molarity multiplied by volume, then type the concentration in mol/L and the volume in millilitres. The calculator multiplies them to get moles before applying the mole ratio, so no separate conversion is needed.

Can this find the limiting reagent?

Indirectly. Run the calculation once from each reactant you actually have; the one that produces the smallest amount of product is the limiting reagent. Everything the tool reports assumes the substance you entered is the one that runs out first.

Related tools