Enter each element with its percentage or its mass. This works through all five steps to the simplest whole-number ratio, and finds the molecular formula too if you give it the molar mass.
The empirical formula is the simplest whole-number ratio of atoms. The molecular formula is how many atoms are actually in one molecule. They are often different.
Glucose is the standard example. Its molecular formula is C6H12O6, but the ratio 6:12:6 simplifies to 1:2:1, so its empirical formula is CH2O. Analysing glucose in a lab gives you CH2O, and you need one extra piece of information, the molar mass, to work back up to the real formula.
After dividing by the smallest, you sometimes get numbers that are not whole, like 1 : 1.5 or 1 : 1.33. Do not round these. A value of 1.5 means the real ratio is 2 : 3, and rounding to 2 would give you the wrong compound entirely.
Instead, multiply every number by whatever turns them all into whole numbers. For 1.5, multiply by 2. For 1.33, which is a third, multiply by 3. For 1.25, a quarter, multiply by 4. This calculator does that automatically and tells you what factor it used.
Genuinely small errors are different. If you get 1.98, that is experimental rounding and the answer is 2. The rule of thumb is that anything within about 0.1 of a whole number can be rounded, and anything further away is a real fraction.