Mole Ratio Calculator
Use the coefficients from a balanced equation to convert moles of one substance into moles of another.
How it works
moles of B = moles of A · (coefficient of B / coefficient of A)
The coefficients in a balanced chemical equation give the fixed ratio in which substances react and form. That ratio is a conversion factor between moles of any two species. Multiplying the known amount by the target-over-known coefficient ratio scales it to the corresponding amount of the other substance.
Worked example
In N₂ + 3H₂ → 2NH₃, the H₂ : N₂ ratio is 3 : 1. Reacting 4 mol H₂ with the ratio for N₂ (1/3) needs 4 × (1/3) = 1.33 mol N₂; here with coefficients 2 and 3, 4 mol of the known gives 4 × (3/2) = 6 mol of the target.
Sources: Stoichiometry — Wikipedia
Frequently asked questions
Where do the coefficients come from?
They are the numbers in front of each formula in a balanced equation. Always balance the equation first, or the ratio will be wrong.
Can I use this for grams?
Not directly — convert grams to moles first (mass ÷ molar mass), apply the mole ratio, then convert back to grams if needed.
Does the ratio depend on how much I have?
No. The mole ratio from the balanced equation is fixed. Only the actual moles you start with change the result.
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