Stoichiometry Calculator

MiniWebtool’s Stoichiometry Calculator uses a balanced reaction’s molar ratios to convert among moles, mass, and supported volume quantities. Follow the equation-based working from a known reactant or product amount.

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Help me understand MiniWebtool's Stoichiometry Calculator: https://miniwebtool.com/stoichiometry-calculator/. What can I use it for, what inputs or settings do I need, and how do I use it and understand the output? Walk me through one simple example. Use this page as your source and answer in English.

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32 g of O2 in 2H2 + O2 -> 2H2O makes 36.03 g of water

Enter a balanced equation, the known substance and its amount, then the substance you want. The result gives the moles and mass with each step of the calculation.

Enter a balanced chemical equation, specify a known quantity, and convert between moles, mass, and volume with step-by-step solutions.

H₂O CO₂ NaCl NH₃

Quick Examples

Balanced Chemical Equation

Use -> or → for the reaction arrow. Coefficients go before formulas (e.g. 2H2O).

Known Substance

Value

Unit

→

Target Substance

Output Unit

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About Stoichiometry Calculator

The Stoichiometry Calculator converts between moles, mass (grams), and volume (liters at STP) for any substance in a balanced chemical equation. It automatically calculates molar masses from chemical formulas and applies molar ratios to perform conversions, showing each step of the solution so you can follow the reasoning.

At a Glance

Stoichiometry Calculator converts between moles, grams and liters of gas at STP for any substance in a balanced chemical equation. It calculates molar masses from formulas and shows each step of the solution.

Stoichiometry Calculator: features at a glance
Feature	What you get	Good for
Equation input	Type a balanced equation such as 2H2 + O2 -> 2H2O. Coefficients and formulas are read automatically.	Reaction problems from chemistry class
Known and target	Pick a known substance and enter its amount in moles, grams or liters, then pick the target substance and output unit.	Finding how much product or reactant is involved
Molar mass	Molar masses are calculated from the chemical formulas, for example H2O = 18.015 g/mol.	Avoiding manual atomic-mass lookups
Molar ratios	Uses the coefficient ratio from the balanced equation to move between substances.	Following the mole-bridge method
Gas volume at STP	Converts gases using 22.414 L per mole at 0 degrees C and 1 atm.	Gas volume questions in lab work
Worked steps	Step-by-step solutions with molar mass calculations, ratio application and unit conversions, plus quick example reactions.	Checking your own working

Key Concepts in Stoichiometry

⚖ Molar Mass

The mass of one mole of a substance in grams per mole (g/mol). Calculated by summing the atomic masses of all atoms in the formula. For example, H₂O = 2(1.008) + 15.999 = 18.015 g/mol.

🔗 Molar Ratio

The ratio of coefficients from a balanced equation. In 2H₂ + O₂ → 2H₂O, the ratio of H₂ to O₂ is 2:1, meaning 2 moles of hydrogen react with every 1 mole of oxygen.

📐 Molar Volume

At Standard Temperature and Pressure (STP: 0°C, 1 atm), one mole of any ideal gas occupies exactly 22.414 liters. This allows direct conversion between moles and volume for gases.

🔄 The Mole Bridge

Stoichiometry problems always go through moles. Convert the known quantity to moles, apply the molar ratio, then convert to the desired unit. This three-step method works for any conversion.

Core Formulas

\( \text{moles} = \frac{\text{mass (g)}}{\text{molar mass (g/mol)}} \)

\( \text{moles} = \frac{\text{volume (L)}}{22.414 \text{ L/mol}} \) (at STP)

\( \text{moles of B} = \text{moles of A} \times \frac{\text{coefficient of B}}{\text{coefficient of A}} \)

How to Use This Calculator

Enter a balanced chemical equation using standard notation (e.g., 2H2 + O2 -> 2H2O). The calculator parses coefficients and formulas automatically.
Select the known substance from the dropdown and enter its quantity. Choose whether the value is in moles, grams, or liters (for gases at STP).
Select the target substance you want to convert to and pick the desired output unit.
Click Calculate to see the step-by-step solution, including molar mass calculations, molar ratio applications, and unit conversions.
Try the quick examples to see how different reaction types work, from water synthesis to the Haber process.

Common Applications

🧫

Lab Preparation

Calculate how much reagent to measure for an experiment

🏭

Industrial Chemistry

Scale reactions for manufacturing and production

💊

Pharmaceutical

Determine drug synthesis quantities and yields

🌍

Environmental Science

Analyze emissions and chemical pollutant reactions

Frequently Asked Questions

What is stoichiometry?

Stoichiometry is the branch of chemistry that deals with the quantitative relationships between reactants and products in a balanced chemical equation. It uses molar ratios from balanced equations to convert between amounts of different substances.

How do you convert grams to moles?

To convert grams to moles, divide the mass in grams by the molar mass of the substance. The molar mass is the sum of atomic masses of all atoms in the chemical formula, measured in grams per mole (g/mol).

What is a molar ratio?

A molar ratio is the ratio of the coefficients of two substances in a balanced chemical equation. For example, in 2H₂ + O₂ → 2H₂O, the molar ratio of H₂ to O₂ is 2:1, meaning 2 moles of hydrogen react with 1 mole of oxygen.

What is molar volume at STP?

At Standard Temperature and Pressure (0°C and 1 atm), one mole of any ideal gas occupies 22.414 liters. This is known as the molar volume at STP and allows conversion between moles and volume for gaseous substances.

Why must the chemical equation be balanced?

A balanced equation ensures conservation of mass and atoms. The coefficients in a balanced equation represent the molar ratios needed for stoichiometric calculations. An unbalanced equation would give incorrect ratios and wrong results.

Reference this content, page, or tool as:

"Stoichiometry Calculator" at https://MiniWebtool.com/stoichiometry-calculator/ from MiniWebtool, https://MiniWebtool.com/

by miniwebtool team. Updated: Mar 16, 2026

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