Enter a chemical formula and choose what to count — then specify the element or ion you're targeting to get the exact count per formula unit, along with the formula mass and total atoms per formula unit.
Count per Formula Unit
--
Formula Mass
--
Total Atoms per Formula Unit
--
A formula unit is the smallest whole-number ratio of ions or atoms represented by a chemical formula. It represents the simplest ratio of elements in an ionic compound or the actual molecular composition in covalent compounds.
Select 'Polyatomic Ion' as your count mode and enter the ion formula exactly as it appears (e.g., PO4, SO4, NO3). The calculator will find all occurrences of that specific ion grouping within the compound.
Yes! The calculator supports parentheses, nesting, and hydrates. Examples include Al2(SO4)3, Ca(OH)2, and CuSO4·5H2O. Make sure to use proper capitalization for element symbols.
Element symbols are case-sensitive. For example, 'Ca' represents calcium, while 'ca' would be interpreted incorrectly. Always use proper capitalization: first letter uppercase, second letter (if any) lowercase.
When counting atoms, you're looking for individual elements (like O or Ca). When counting ions, you're looking for specific groupings that act as units (like PO4³⁻ or SO4²⁻). The calculator can count both depending on your selection.
Hydrates use dot notation (·) to separate the main compound from water molecules. For example, CuSO4·5H2O contains 1 copper, 1 sulfur, and 9 oxygen atoms (4 from SO4 plus 5 from water molecules).
The calculator counts one element or ion at a time, but it provides a complete breakdown table showing all elements present in the formula unit. This lets you see the count for every element simultaneously.