Stoichiometry Calculator
Calculate how much of one substance corresponds to a known amount of another using a balanced chemical equation.
Result
34.062gNH₃
28.014 g N₂ → 34.062 g NH₃
Calculated from 28.014 g N₂ using the 1:2 mole ratio.
See the calculation
From N₂ to NH₃
Convert the known amount to moles
28.014 g ÷ 28.014 g/mol = 1.000 mol N₂
Apply the mole ratio
From 1 N₂ : 2 NH₃
1.000 mol N₂ × 2/1 = 2.000 mol NH₃
Convert target moles to the requested unit
2.000 mol × 17.031 g/mol = 34.062 g NH₃
Final34.062 g NH₃
Mole ratio
N₂ : NH₃ = 1 : 2
2 ÷ 1 = 2
The ratio comes from the coefficients in the balanced equation, not the subscripts in the formulas.
Substances
Reaction overview
| Substance | Role | Coefficient | Molar mass |
|---|---|---|---|
| N₂ | Reactant | 1 | 28.014 g/mol |
| H₂ | Reactant | 3 | 2.016 g/mol |
| NH₃ | Product | 2 | 17.031 g/mol |
Important concept
Stoichiometry uses mole ratios
The coefficients in a balanced chemical equation represent mole ratios. For 2H₂ + O₂ → 2H₂O, the equation tells us:
- 2 mol H₂ reacts with 1 mol O₂
- 2 mol H₂ produces 2 mol H₂O
- 1 mol O₂ produces 2 mol H₂O
The coefficients do not directly represent gram ratios.
How it works
Three conversions
Convert the known amount to moles
Divide the known mass by its molar mass.
n = m ÷ M
Apply the coefficient ratio
Multiply by the target coefficient over the known coefficient.
target moles = known moles × target coefficient ÷ known coefficient
Convert to the requested target unit
Multiply by the target molar mass, or stop here for a result in moles.
m = n × M
What is stoichiometry?
Stoichiometry is the calculation of the quantitative relationship between substances in a chemical reaction.
A balanced equation gives the mole ratios; molar mass moves between grams and moles.
Concepts
Coefficients, subscripts, and balancing
Coefficients are the mole ratio
In:
2H₂ + O₂ → 2H₂O
the coefficients give:
2 mol H₂ : 1 mol O₂ : 2 mol H₂O
Subscripts are not coefficients
The subscript in H₂O counts hydrogen atoms in one molecule. The coefficient in 2H₂O counts moles taking part in the reaction. Subscripts never form the mole ratio.
Why must the equation be balanced?
The coefficients provide the mole ratio between the substances in the reaction. An unbalanced equation gives no valid ratio. Use the Chemical Equation Balancer first.
Scope
What this calculator includes
This calculator converts an amount of one substance to another using a balanced chemical equation.
It handles:
- Mole ratios between any two substances
- Reactant to product and product to reactant
- Grams to moles and moles to grams
- Validation that the equation is balanced
- Full precision, rounded only for display
Use another Chemistry Inspect tool for:
FAQ
Frequently asked questions
What is a stoichiometry calculator?
It uses the mole ratios in a balanced chemical equation to calculate how much of one substance corresponds to a known amount of another.
Does the equation need to be balanced?
Yes. The coefficients must represent the correct mole ratio before the calculation can be performed.
How do I calculate grams from grams?
Convert the known grams to moles, apply the mole ratio, then convert the target moles back to grams.
Can I use moles instead of grams?
Yes. You can enter the known amount in moles and request the result in moles or grams.
What is a mole ratio?
It is the ratio between the coefficients of two substances in a balanced chemical equation.
Why can't I use the subscripts as the ratio?
Subscripts describe the composition of a substance. Coefficients describe the relative amounts participating in the reaction.
Can this calculator balance an equation?
No. It requires a balanced equation. Use the Chemical Equation Balancer first.
Does this find the limiting reagent?
No. If you have amounts for multiple reactants and need to know which one runs out first, use the Limiting Reagent Calculator.
Why do I get a different answer from another calculator?
Differences can come from atomic-weight datasets, displayed precision, or rounding. Chemistry Inspect keeps full precision through the calculation and rounds only for display.
Can I convert directly from grams of one substance to grams of another?
Yes, but the calculation passes through moles internally: grams → moles → mole ratio → moles → grams.