Empirical Formula Calculator
Convert percent composition or masses to simplest formula ratios.
Convert percent composition or measured masses into the simplest whole-number formula. Any elements work, not just carbon, hydrogen, and oxygen, and adding a molecular mass converts the empirical formula into the molecular formula.
Combustion analysis gives masses of CO₂ and H₂O; convert those to grams of C and H first, then find oxygen by difference.
How to Use the Empirical Formula Calculator
1
Enter the composition. Add a row for each element with either its percentage of the sample or its measured mass in grams.
2
Add a molecular mass (optional). Supplying the measured molecular mass converts the empirical formula into the molecular formula.
3
Read the mole table. The result shows moles, the ratios after dividing by the smallest value, any scaling multiplier used, and the final formula.
What is the Empirical Formula Calculator?
The empirical formula calculator converts percent composition or measured masses into the simplest whole-number ratio of atoms. It divides each element's mass by its atomic mass, normalizes by the smallest mole value, and clears common fractions to reach the empirical formula.
This is a classic multi-step problem where small rounding errors snowball. The calculator keeps full precision until the final ratio step and shows the intermediate mole values, so you can see exactly where a hand calculation went wrong.
Common Uses
- Convert percent composition to an empirical formula
- Find formulas from combustion analysis masses
- Check a molecular formula against its empirical ratio
- Practice mole-ratio normalization
How to Solve It by Hand
Manual calculation is still important: identify the known variables, convert units before substitution, apply the equation, and check whether the result is chemically reasonable. The most common mistakes are inconsistent units, constants rounded too early, and skipping the interpretation step.
Practice Prompt
Try changing the default values and ask the lower-right chemistry chat why the result increased or decreased. That turns the calculator from a number machine into a study loop.
Assume a 100 g sample so each percentage becomes grams, divide each mass by that element's atomic mass to get moles, divide every mole value by the smallest one, and scale the ratios up to whole numbers if needed.
The empirical formula is the simplest whole-number atom ratio; the molecular formula is the actual count in one molecule. Glucose has empirical formula CH2O and molecular formula C6H12O6, six times larger.
Divide the measured molecular mass by the empirical formula mass and round to the nearest whole number, then multiply every subscript by that factor. Enter a molecular mass in the calculator and it does this step for you.
Multiply all of them by the smallest integer that clears the fraction — 2 for a .5, 3 for a .33 or .67, 4 for a .25 or .75. The calculator searches multipliers up to 12 automatically and tells you which one it used.
Convert the CO2 mass to grams of carbon and the H2O mass to grams of hydrogen, then find oxygen by subtracting those from the original sample mass. Enter the resulting masses in mass mode.