Stoichiometry is the calculation of reactants and products in chemical reactions using the mole ratio from balanced equations.

Steps:

1. Convert given amount to moles
2. Use mole ratio to find moles of unknown
3. Convert moles to desired units

Example: For 2H₂ + O₂ → 2H₂O, the mole ratio of H₂ to H₂O is 2:2 or 1:1.