Chemistry

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Molar Ratio Calculator.

Calculate a two-component molar ratio and normalized fractions.

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01

Set your values

Results update as you type.

A:B ratio: 2

A:B ratio

2.000000
Fraction A: 0.666667

Fraction A

0.666667
Fraction B: 0.333333

Fraction B

0.333333

Educational arithmetic only. Keep units consistent and use measured or explicitly supplied chemistry inputs; this tool does not infer reaction pathways, property tables, or safety guidance.

Use Cases

Stoichiometry in chemical reactions

Determine the molar ratio of reactants or products to balance equations or plan experiments.

Example: If a reaction needs 2 mol A and 3 mol B, the ratio is 2:3.

Preparing mixtures with specific proportions

Calculate the normalized fractions to know the exact composition of a two-component mixture.

Example: Mixing 1 mol of salt with 4 mol of water gives fractions 0.2 and 0.8.

Frequently Asked Questions

What is a molar ratio?
A molar ratio is the proportion of moles of one substance to another in a chemical mixture or reaction. This calculator gives the ratio of Component A to Component B based on the moles you enter.
How are normalized fractions calculated?
Normalized fractions show each component's share of the total moles. For example, if you have 2 mol of A and 3 mol of B, the total is 5 mol, so A's fraction is 2/5 = 0.4 and B's is 3/5 = 0.6.
Can I use this calculator for any two-component system?
Yes, as long as you have the amounts in moles for both components. It works for mixtures, solutions, or reaction stoichiometry where you need the molar ratio and fractions.

Tips & Common Mistakes

Tips

  • Ensure both values are in moles; convert grams to moles using molar mass if needed.
  • Double-check your inputs for accuracy, as the ratio and fractions depend directly on them.
  • Use the normalized fractions to quickly see the percentage of each component in the mixture.
  • For reactions, remember that molar ratios can be simplified, but the calculator gives the exact ratio from your inputs.

Common Mistakes to Avoid

  • Entering grams instead of moles – always convert to moles first.
  • Mixing up the order of components – the ratio is A:B, so keep consistent.
  • Forgetting that fractions must sum to 1 – if they don't, recheck your inputs.

Last updated: August 13, 2026