Frequently Asked Questions
Everything you need to know about the Stoichiometry Calculator.
What is stoichiometry?
Stoichiometry is the calculation of relative quantities of reactants and products in a chemical reaction, based on the balanced equation's mole ratios.
What is a mole ratio?
A mole ratio is the ratio between the coefficients of two species in a balanced chemical equation. It's used to convert moles of one substance into moles of another.
How do I convert grams to moles?
Divide the mass in grams by the substance's molar mass (in g/mol) to get moles.
What is Avogadro's number used for?
Avogadro's number (6.022×10²³) converts between moles and the number of individual particles (atoms, molecules, or formula units) of a substance.
Does the equation need to be balanced?
Yes. The mole-ratio calculation depends on the coefficients being correct for a balanced equation; an unbalanced equation will give an incorrect ratio.
Can I use parentheses in chemical formulas?
Yes, formulas like Ca(OH)2 or Al2(SO4)3 are supported, including nested groups with a subscript multiplier.
Can I convert from a product back to a reactant?
Yes, choose any species in the equation as the known and any other as the target — the mole ratio works in either direction.
What units can I enter the known amount in?
You can enter the known amount in grams, moles, or particles; the calculator converts it to moles internally before applying the mole ratio.
Does this calculator find the limiting reagent?
No — this calculator converts between moles, mass, and particles for a single known-to-target pair. For finding the limiting reagent among multiple reactants, use the Limiting Reagent Calculator.
Is this calculator free to use?
Yes, the stoichiometry calculator is completely free with no sign-up, and all calculations run instantly in your browser.