Binary acids: hydro + anion root + ic acid (HCl → hydrochloric acid). Oxoacids follow ate → ic and ite → ous patterns (nitrate → nitric acid; nitrite → nitrous acid).

Hydrates append a centered dot and water count: CuSO4·5H2O is copper(II) sulfate pentahydrate.

Chemical Name ⇄ Formula Calculator

Q: How do you decide ionic vs covalent?

If a metal (or polyatomic cation) pairs with a nonmetal or a polyatomic anion, the compound is ionic. Nonmetal + nonmetal is covalent and uses Greek prefixes.

Q: When do I use Roman numerals?

Use Roman numerals for metals with variable oxidation states (many transition metals), such as iron(II) vs iron(III). The numeral is determined from charge balance.

Convert between a chemical name and its formula. Supports ionic, covalent (prefix), binary acids, oxoacids, hydrates, and common polyatomic ions. Includes step-by-step logic and an optional element-count chart.

Background

Naming depends on compound class. Ionic names use cation + anion (Roman numerals for variable-charge metals). Covalent names use Greek prefixes. Binary acids follow hydro-…-ic acid; oxoacids follow …ate→…ic and …ite→…ous. Hydrates append • nH₂O as n-hydrate.

Enter a name or a formula:

Name or formula:

Tip: Works both directions. Try “sodium carbonate”, “glucose”, “tetraphosphorus decaoxide”, “H2SO4”, or “copper(II) sulfate pentahydrate”.

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Step-by-step reasoning

Mini chart: element counts

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How to use this calculator

Input: Type either a chemical name or a formula. We auto-detect and convert the other way.
Classes: Supports ionic, covalent (prefix), binary acids (hydro-…-ic), oxoacids (…ate→…ic / …ite→…ous), and hydrates (• nH₂O).
Transition metals: Adds Roman numerals when determinable from charge balance.
Polyatomic ions: Recognizes a comprehensive set in both directions.

Formula & Equation Used

Ionic: name = cation [+ Roman numeral if variable] + anion (ide or polyatomic name). Stoichiometry from charge balance.

Covalent: name = (Greek prefix) + element + (Greek prefix) + element root + “ide”. No “mono” on the first element.

Binary acids: hydro + anion root + “ic acid” (HCl → hydrochloric acid).

Oxoacids: oxyanion “ate” → “ic acid”, “ite” → “ous acid” (e.g., nitrate → nitric acid; nitrite → nitrous acid).

Hydrates: “• nH₂O” → “n-hydrate” (mono-, di-, tri-, …, deca-).

Examples

FeCl₃ → iron(III) chloride

Cl is −1; three chlorides require Fe at +3 → iron(III) chloride.

dinitrogen monoxide → N₂O

di- (2) and mono- (1) → N₂O. No “mono” on first element.

HNO₃ → nitric acid

Nitrate → nitric acid (ate → ic).

CuSO₄·5H₂O → copper(II) sulfate pentahydrate

SO₄ is 2− → Cu²⁺; five waters → pentahydrate.

Frequently Asked Questions

Q: How do you decide ionic vs covalent?

Metal (or polyatomic cation) + nonmetal/polyatomic anion → ionic. Nonmetal + nonmetal → covalent with prefixes.

Q: When do I use Roman numerals?

For metals with variable oxidation states (e.g., iron(II)/iron(III)). We infer from charge balance when possible.

Q: How are acids named?

Binary acids: hydro + root + ic acid (HCl → hydrochloric acid). Oxoacids: oxyanion ate→ic, ite→ous (HNO₃ nitric acid; HNO₂ nitrous acid).

Q: What about hydrates?

Use a centered dot and prefix: CuSO₄·5H₂O → copper(II) sulfate pentahydrate.

Polyatomic Ions