Stoichiometry Calculator
Solve stoichiometric reactant and product balances from balanced or unbalanced chemical equations. Enter chemical formulas using standard notation, specify the starting grams, moles, or molecules of any compound, and the stoichiometry calculator instantly balances the reaction and details all corresponding amounts — all running privately in your browser with no signup required.
Enter an unbalanced or balanced chemical equation (e.g. Fe + O2 -> Fe2O3). Select a given substance and its amount, and the stoichiometry calculator will automatically balance the reaction and compute corresponding masses, moles, and particle counts for all species.
Quick Presets
Separate reactants and products with -> or → and compounds with +.
Why Use Our Stoichiometry Calculator?
Equation Balancing & Solving
Enter any balanced or unbalanced chemical equation. The stoichiometry calculator automatically balances the reaction in milliseconds using rational Gaussian elimination before calculating quantities.
Secure Stoichiometry Calculator Online
The stoichiometry calculator executes 100% locally in your browser. None of your chemical equations, concentrations, or calculation results are uploaded to a server or tracked. Perfect for academic privacy.
No Installation or Chemistry Apps Required
Our stoichiometry calculator runs instantly in any modern web browser on desktop, mobile, or tablet. Supports complex equations, parentheses, and polyatomic ionic formulas with no setup required.
Mass, Mole, and Particle Conversions
Convert freely between grams (g), moles (mol), and molecules or atoms. Specify the given amount of any reactant or product to solve for all remaining substances in one unified table.
Common Use Cases for Stoichiometry Calculator
Theoretical Yield Calculations
Determine the maximum amount of product that can be generated from a specific amount of reactant. Select the reactant, enter its starting mass, and view the theoretical yield of all products.
Laboratory Preparation
Calculate exactly how many grams of a starting reactant are required to produce a desired mass of product. Handy for weighing chemicals and setting up synthesis reactions.
Limiting and Excess Reactant Analysis
Use calculated molar amounts to compare starting reactant ratios. Finding how much of each reactant is needed allows chemists to optimize reaction mixtures and reduce waste.
Percent Yield Reference Data
Compare actual experimental product mass with the theoretical stoichiometric output calculated here to compute the percent yield of chemical processes.
Industrial Chemical Synthesis Scaling
Scale up chemical recipes from bench-top grams to large-scale industrial kilograms. The stoichiometry calculator maintains exact mass balances for all species.
Chemistry Education & Homework
Verify manual calculations for chemistry exams and homework. The calculator lists step-by-step conversions showing molar masses and coefficient multipliers.
Understanding Stoichiometry and Stoichiometric Calculations
What is Stoichiometry?
Stoichiometry (from the Greek stoicheion meaning element, andmetron meaning measure) is the quantitative relationship between the reactants and products in a chemical reaction. Based on the Law of Conservation of Mass, stoichiometry dictates that the mass of the reactants must equal the mass of the products, meaning the number of atoms of each element remains identical on both sides of a balanced equation. Our online stoichiometry calculator balances your equations and solves mole-to-mole, mass-to-mass, and particle-to-particle conversions instantly.
How to Calculate Stoichiometry Step-by-Step
- Balance the Chemical Equation: Determine the stoichiometric coefficients for the reactants and products. If the reaction is unbalanced, the stoichiometry calculator solves the linear null-space equations using Gaussian elimination to find the smallest integer coefficients.
- Convert Given Amount to Moles:Moles serve as the chemical bridge. If you are given a mass in grams, divide it by the substance's molar mass ($n = m / M$). If you are given a molecule count, divide by Avogadro's number ($6.022 \times 10^23$).
- Multiply by the Mole Ratio (Stoichiometric Factor): Determine the moles of the target substance by multiplying the given moles by the ratio of coefficients from the balanced equation:
Target Moles = Given Moles × (Target Coeff / Given Coeff) - Convert Moles to the Desired Unit:Finally, convert the target substance's moles back to grams (multiply by its molar mass) or molecules (multiply by Avogadro's number).
Core Stoichiometric Concepts Explained
- Balanced Equation: A representation where the sum of each atom species on the reactant (left) side matches the product (right) side. Stoichiometric calculations cannot be performed without a balanced reaction.
- Stoichiometric Coefficients: The integers preceding chemical formulas (e.g. the 2 in 2H₂O) indicating the relative mole ratios in which compounds react.
- Avogadro's Number: Exactly $6.02214076 \times 10^23$ particles (atoms, molecules, or ions) per mole, bridging macroscopic grams and microscopic atoms.
Supported Equation Formats
The stoichiometry calculator parses standard chemical equations like: simple additions (H₂ + O₂ → H₂O), combustion reactions (CH₄ + O₂ → CO₂ + H₂O), metal-acid displacements (Al + HCl → AlCl₃ + H₂), and complex precipitations(KMnO₄ + HCl → KCl + MnCl₂ + H₂O + Cl₂). Use standard parentheses for ionic groups (e.g. Fe2(SO4)3). Element symbols are case-sensitive (e.g., Fe, not FE or fe) to ensure correct element database matching.
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Frequently Asked Questions About Stoichiometry Calculator
A stoichiometry calculator is an online chemistry tool that solves the quantitative mass, mole, and particle relationships in a chemical reaction. Our stoichiometry calculator automatically balances the chemical equation and computes corresponding amounts for all reaction species based on one given value.
The calculator uses Gaussian elimination over rational numbers to determine the null-space vector of the atomic composition matrix. This yields the smallest possible positive integer coefficients to balance the equation perfectly, ensuring mass is conserved.
Yes. The stoichiometry calculator runs 100% client-side in your web browser. Your inputs, chemical formulas, concentrations, and results are processed locally on your device and are never uploaded to any server or tracked.
Yes, the calculator is 100% free to use with no account signups, subscriptions, or limits. You can perform as many chemical stoichiometry calculations as you need.
A mole ratio is the ratio of the coefficients of any two compounds in a balanced chemical equation. For example, in the reaction 2H₂ + O₂ → 2H₂O, the mole ratio of H₂ to O₂ is 2:1, meaning 2 moles of hydrogen are required for every 1 mole of oxygen.
Avogadro's number (6.022 × 10²³) is the number of particles in one mole of a substance. The calculator uses it to convert between moles and particle counts (atoms or molecules) for reactants and products.
The balancing algorithm will fail if the equation is chemically impossible (e.g. elements appear on one side but not the other), if element symbols are capitalized incorrectly (e.g. fe instead of Fe), or if the formatting is incorrect. Verify element symbols and arrow notation (->).
The limiting reactant is the substance that is completely consumed first in a chemical reaction, limiting the amount of product that can be formed. While this calculator computes theoretical ratios from a single starting amount, comparing the calculated requirements of reactants to your actual starting amounts identifies which reactant is limiting.