Empirical Formula Calculator
Turn masses or percentages of elements into the simplest whole-number formula.
What is Empirical Formula?
The empirical formula is the simplest whole-number ratio of atoms in a compound — glucose's molecular formula is C6H12O6 but its empirical formula is CH2O. It is what an elemental analysis determines: burn a sample, weigh the products, and the ratio falls out of the mole arithmetic.
How it works
Divide each mass by that element's atomic mass to convert to moles, then divide every result by the smallest one, and multiply up by whatever integer makes them all whole. The table shows every one of those steps. Percentages are accepted directly as long as they total 100%, and the tool says so when they do not.
- Enter what you know. Every field recalculates as you type — there is no submit button. Leave the quantity you want blank and the page solves for it.
- Read the answer and the working. The result appears above the fold; underneath it is the formula with your numbers substituted, so the arithmetic can be checked rather than trusted.
- Check the units and the size. Units are shown on every value and selectable per field, so a result in kJ, kPa or km/h is converted rather than assumed. Sanity-check the magnitude against a known landmark such as 1 g/cm³ for water.
Examples
A textbook problem with a known answer
Every tool here is checked against standard example problems — the molar mass of C6H12O6 is 180.16 g/mol, and free fall from 20 m takes about 2.02 s at g = 9.8 m/s².
A result you want to reason backwards from
Leave the quantity you already know blank instead: given the final answer, most tools recover the starting value — the mass needed for a target concentration, or the height a fall must have had.
Common mistakes
Forgetting that a formula is only as good as its subscripts
H2O and H2O2 are different compounds. The formula field shows its parse — element by element — so a mis-typed subscript is visible before it reaches the arithmetic.
Mixing units in the middle of a calculation
The most common source of a wrong answer is a value in grams next to a formula expecting kilograms, or Celsius next to a gas constant expecting kelvin. This category converts on the way in and labels what it used.
Frequently asked questions
What if the ratio does not come out as whole numbers?
It usually will once you multiply up: a ratio of 1 : 1.5 : 0.5 is 2 : 3 : 1 and therefore C2H3O. If no small multiplier works, the tool says so rather than rounding — that normally means a mass is wrong.
Can I use percentages instead of masses?
Yes — percentages work directly, since the ratio is unaffected by the sample size. They must total 100% within rounding, and the tool tells you the total it computed.
How is this different from the molecular formula?
The empirical formula is the reduced ratio; the molecular formula is that same ratio multiplied by an integer. CH2O could be formaldehyde (CH2O) or glucose (C6H12O6) — the molar mass decides which.