๐งซEmpirical Formula Calculator
Find the empirical and molecular formula of a compound from percent composition or mass data, with full step-by-step mole-ratio working.
Free Empirical Formula Calculator
Trying to work out a compound's empirical formula from lab data? Our free empirical formula calculator does the mole-ratio math for you. Enter either the percent composition or the raw mass of each element, and it converts everything to moles, divides by the smallest value, and simplifies to the lowest whole-number ratio โ showing every step along the way.
It handles the tricky parts too: when ratios don't land on whole numbers, it explains the multiplication step needed to clear them, instead of just rounding and hoping for the best. If you know the compound's molecular molar mass, it will also derive the full molecular formula from your empirical result.
Built for chemistry students checking homework or verifying lab calculations, it runs entirely in your browser. No sign-up, no downloads. See the About page or the FAQ for more.
About the Empirical Formula Calculator
Features
Two input modes
Percent composition (validated against 100%) or raw mass data with any number of rows.
Atomic weight lookup
A built-in table of common elements; unrecognized symbols are flagged.
Mole-ratio derivation
Each step โ moles, division by smallest, and any multiplier applied โ is shown explicitly.
Non-integer ratio handling
Ratios like x.5 are cleared by multiplying by the correct small integer, explained in the working.
Optional molecular formula
Supply a known molar mass to derive the full molecular formula from the empirical result.
Frequently Asked Questions
How does the empirical formula calculator work?
Enter percent composition or mass for each element; it converts to moles, finds the smallest whole-number ratio, and shows every step.
Is it free?
Completely free, no sign-up, downloads, or limits.
What's the difference between empirical and molecular formula?
The empirical formula is the simplest whole-number ratio of atoms; the molecular formula is the actual ratio, which can be a multiple of the empirical formula.
Can it find the molecular formula too?
Yes โ if you provide the compound's known molar mass, it calculates the multiplier and derives the molecular formula.
What if my percentages don't add up to 100%?
It flags this; you can also use the "solve remaining % as oxygen" option for the classic combustion-analysis problem type.
What if the mole ratio isn't a whole number?
The calculator multiplies all ratios by the smallest integer needed to clear fractions, and shows this step explicitly.
Which elements are supported?
The most common elements by standard atomic weight; unrecognized symbols are flagged.
Does it show the steps?
Yes, the full mole-ratio derivation is shown, not just the final formula.
Is my data stored?
No; everything runs in your browser and isn't stored or sent anywhere.
Does it work on mobile?
Yes, fully responsive on all screen sizes.