Last updated: June 2026
Use this chemical name and formula calculator to convert common school-level inorganic formulae into names, and names into formulae. It supports simple ionic compounds, transition-metal compounds with Roman numerals, common polyatomic ions, simple covalent compounds, common acids and hydrates.
- Enter either a chemical formula, such as FeCl3, or a chemical name, such as iron(III) chloride.
- Select Convert. The calculator automatically decides whether to convert formula to name or name to formula.
- Keep “Show step-by-step reasoning” selected to see the naming or charge-balancing method.
- Select “Show element counts” to display the number of atoms of each element.
- Use the example buttons to test ionic compounds, covalent compounds, acids and hydrates.
Chemical Name Calculator
When a formula such as FeCl3 is entered, the calculator identifies the ions and determines the charge on the metal ion.
Chloride has a charge of −1. Three chloride ions give a total charge of −3, so iron must have a charge of +3. The Roman numeral is therefore III.
Chemical Formula Calculator
When a name such as sodium carbonate is entered, the calculator uses ion charges to construct a neutral formula.
Two sodium ions are required to balance one carbonate ion. The smallest whole-number ion ratio is therefore 2:1.
Naming ionic compounds
Ionic compounds are named by writing the cation first and the anion second. Fixed-charge metals do not require Roman numerals.
Variable-charge metals require Roman numerals because the same metal can form ions with different charges.
Common polyatomic ions
Polyatomic ions contain several covalently bonded atoms but behave as one charged unit when ionic formulae are written.
| Ion | Name | Charge |
|---|---|---|
| NH4+ | ammonium | +1 |
| OH− | hydroxide | −1 |
| NO3− | nitrate | −1 |
| SO42− | sulfate | −2 |
| CO32− | carbonate | −2 |
| PO43− | phosphate | −3 |
Naming simple covalent compounds
Simple binary covalent compounds use Greek prefixes to show how many atoms of each element are present.
| Prefix | Number |
|---|---|
| mono- | 1 |
| di- | 2 |
| tri- | 3 |
| tetra- | 4 |
| penta- | 5 |
| hexa- | 6 |
Naming common acids
Some common acids are recognised directly because their names are normally memorised at school level.
Naming hydrates
Hydrates contain water of crystallisation. The prefix after the ionic-compound name tells you how many water molecules are present.
Worked examples
Example 1: FeCl3
Three chloride ions contribute a total charge of −3. Iron must therefore be Fe3+, so the compound is iron(III) chloride.
Example 2: Calcium hydroxide
Calcium is Ca2+ and hydroxide is OH−. Two hydroxide ions are needed, so brackets are used around the repeated polyatomic ion.
Common exam traps
Frequently Asked Questions
What does a chemical name calculator do?
It converts supported chemical formulae into names, such as FeCl3 into iron(III) chloride.
What does a chemical formula calculator do?
It converts supported chemical names into formulae, such as sodium carbonate into Na2CO3.
Does this calculator handle transition metals?
Yes. It supports several common variable-charge metals and can infer the Roman numeral from a valid ionic formula.
Does this calculator handle organic compounds?
It recognises a few common names such as methane and glucose, but it is not a full organic IUPAC naming calculator.
Why is the correct formula important?
Students need the correct formula before calculating molar mass, mole ratios, percentage composition or balanced equations.