#1 Free Stoichiometry Calculator 2025

Stoichiometry is a section of chemistry that involves using relationships between reactants and/or products in a chemical reaction to determine desired quantitative data. It is based on the Law of Conservation of Mass, which states that matter is neither created nor destroyed in a chemical reaction.

Key Concepts:

• Balanced Chemical Equation: Represents the reactants and products with their respective stoichiometric coefficients. These coefficients indicate the mole ratios in which substances react and are formed. Example: 2H₂ + O₂ → 2H₂O means 2 moles of hydrogen react with 1 mole of oxygen to produce 2 moles of water.
• Mole (mol): The SI unit for amount of substance. One mole contains Avogadro's number (approx. 6.022 x 10²³) of entities (atoms, molecules, ions, etc.).
• Molar Mass (MM): The mass of one mole of a substance, typically expressed in grams per mole (g/mol). It is numerically equal to the atomic or molecular weight on the periodic table.
• Mole Ratio: Derived from the coefficients in a balanced chemical equation. It's used to convert moles of one substance to moles of another substance in the reaction.

Core Calculation Steps:

1. Convert known quantity to moles: If your given quantity is in grams, use its molar mass to convert to moles:
   Moles = Grams / Molar Mass
2. Use mole ratio: Apply the mole ratio from the balanced equation to find the moles of the desired substance:
   Moles of Find = Moles of Given × (Coefficient of Find / Coefficient of Given)
3. Convert moles of desired substance to grams (if needed): If the answer is required in grams, use the molar mass of the desired substance:
   Grams = Moles × Molar Mass

Limiting Reactant (Not covered by this specific calculator version): In reactions with multiple reactants, one reactant may be completely consumed before others. This is the limiting reactant, and it determines the maximum amount of product that can be formed (theoretical yield).

1. Define Chemical Equation Components:
   • For each substance involved in your balanced chemical reaction (up to 4), enter its:
     • Name: (e.g., "H2O", "Oxygen"). This is for your reference and will appear in dropdowns.
     • Coefficient: The stoichiometric coefficient from the balanced equation (must be a positive number).
     • Molar Mass (g/mol): The molar mass of the substance (must be a positive number).
   • Only fill in details for substances actually in your reaction. Leave fields for unused substance slots blank or their coefficients/molar masses as 0.
2. Specify the "Given" Substance:
   • Select Substance: Choose the substance for which you have a known quantity from the dropdown. Only substances with valid names, coefficients, and molar masses will be listed.
   • Amount: Enter the known amount of this substance.
   • Unit: Select whether the amount is in 'grams' or 'moles'. If 'grams' is selected, its molar mass must have been provided.
3. Specify the "Find" Substance:
   • Select Substance: Choose the substance you want to calculate the quantity for.
   • Unit: Select whether you want the result in 'grams' or 'moles'. If 'grams' is selected, its molar mass must have been provided.
4. Click the "Calculate" button.
5. View the results, step-by-step solution, and calculation flow animation below.