π§ͺ Stoichiometry Calculator
Convert between grams and moles using mole ratios from balanced equations.
Enter the known substance, target substance, and coefficients from your balanced equation.
Known Substance
Target Substance
How to Use This Calculator
This calculator converts the mass of a known substance into the mass of a target substance using mole ratios from a balanced chemical equation. You need to know the molar masses of both substances and the coefficients in front of each one in the balanced equation.
Enter the mass of the known substance in grams, along with its molar mass in g/mol. For example, if you have 10 g of Hβ with molar mass 2.016 g/mol, type those values on the left.
Enter the stoichiometric coefficient for the known substance from your balanced equation. For 2Hβ + Oβ β 2HβO, the coefficient for Hβ is 2.
Fill in the molar mass and coefficient for the target substance on the right. For water (HβO), the molar mass is 18.015 g/mol and the coefficient is 2.
Click Calculate to see the mass of the target substance, the moles of each, and the mole ratio.
Stoichiometry Formula
The first step converts grams to moles by dividing by molar mass. The second step applies the mole ratio from the balanced equation, where coef_target and coef_known are the coefficients written in front of each substance. The third step converts back to grams by multiplying moles by the target's molar mass. Every stoichiometry problem in general chemistry follows this exact three-step path.
Worked Examples
Where This Calculation Comes Up
Stoichiometry is the backbone of quantitative chemistry. In the lab, you use it to figure out exactly how much of each reactant to weigh before starting a reaction. If you are synthesising aspirin from salicylic acid and need to know how many grams of acetic anhydride to add, stoichiometry gives you the answer. You also use it to determine theoretical yield, which you then compare against what you actually collected to get percent yield.
Outside the teaching lab, stoichiometry shows up in industrial process design, pharmaceutical manufacturing, and environmental science. A chemical plant producing ammonia by the Haber process (Nβ + 3Hβ β 2NHβ) needs to know exactly how many tonnes of hydrogen gas to feed in for every tonne of nitrogen. Even baking uses stoichiometric thinking: recipes scale ingredient amounts proportionally, which is the same principle applied to everyday life.
Frequently Asked Questions
What is stoichiometry?
Stoichiometry is the calculation of quantitative relationships between reactants and products in chemical reactions based on balanced equations.
How do I use mole ratios?
From the balanced equation coefficients, the mole ratio of any two substances gives the conversion factor between their amounts.
Example: How many grams of HβO from 10g Hβ (2Hβ + Oβ β 2HβO)?
10g Hβ Γ· 2.016 g/mol = 4.96 mol Hβ Γ (2 mol HβO / 2 mol Hβ) Γ 18.015 g/mol = 89.35 g HβO
What is a mole?
One mole = 6.022Γ10Β²Β³ particles. It's the bridge between atomic-scale masses and laboratory-scale masses.
Why must the equation be balanced first?
Stoichiometry relies on conservation of mass and atoms. An unbalanced equation gives incorrect mole ratios.