Empirical Formula Calculator: Percent
This empirical formula calculator turns a percent composition or a set of masses into the simplest whole-number formula of a compound. Enter each element symbol with its percent by mass or its mass in grams. The tool converts each amount to moles with standard atomic masses, divides by the smallest mole value, and multiplies by 2, 3 and so on when needed to clear ratios like 1.5 or 1.33. Add the molar mass of the compound to get the molecular formula too. For example, 40.0% C, 6.71% H and 53.3% O gives CH₂O, and a molar mass of 180.16 g/mol makes it C₆H₁₂O₆.
Empirical Formula Calculator
Turn percent composition or grams into the empirical formula, and the molecular formula from molar mass.
How to use the Empirical Formula Calculator
- Choose percent by mass or grams.
- Enter each element symbol and its amount.
- Add the molar mass if you know it.
- Read the formula and the mole table.
Empirical formula steps
moles = mass ÷ atomic mass · ratio = moles ÷ smallest moles · multiply to whole numbers · n = molar mass ÷ empirical formula mass
Features
- Percent or gram input
- Atomic masses for elements 1–92
- Clears ratios like 1.5 and 1.33
- Molecular formula from molar mass
- Step-by-step mole table
Frequently asked questions
How do you find an empirical formula?
Assume 100 g so percentages become grams, convert each mass to moles, divide every mole value by the smallest one, and round to whole numbers, multiplying first if a ratio ends in .5, .33 or .25.
What is the difference between empirical and molecular formula?
The empirical formula is the simplest ratio, like CH₂O. The molecular formula is the actual count of atoms, like C₆H₁₂O₆ for glucose, which is a whole-number multiple of it.
How do I get the molecular formula from the empirical formula?
Divide the molar mass of the compound by the mass of the empirical formula. For glucose, 180.16 ÷ 30.03 = 6, so multiply CH₂O by 6.
What if the percentages do not add up to 100?
Small gaps from rounding are fine. If one element is missing, it is often oxygen, so add it as 100 minus the total of the others.
What do I do with a ratio like 1.5?
Multiply all ratios by 2. A ratio of 1 : 1.5 becomes 2 : 3, which is why iron(III) oxide is Fe₂O₃.