IUPAC Calculator

The IUPAC calculator on this page builds systematic names from three pieces of information: the number of carbons in the longest continuous chain, the highest-priority functional group, and the locants and types of any substituents. It follows the 2013 IUPAC recommendations for preferred names of simple open-chain hydrocarbons and their common derivatives.

How the IUPAC Calculator Works

1. Pick the parent chain length from 1 (methane) to 20 (icosane). The stem is the root name, for example prop- for three carbons.
2. Select the principal functional group. The group with the highest priority controls the suffix: carboxylic acid beats aldehyde beats ketone beats alcohol beats amine beats alkyne beats alkene beats alkane.
3. Add the locant for the functional group where needed. The calculator numbers from the end that gives the lowest locant to the principal group.
4. Add methyl or chloro substituents. Prefixes are listed alphabetically (chloro before methyl), with di, tri, tetra multipliers for repeated groups.

Parent Chain Stems (Carbons 1-20)

Carbons	Stem	Carbons	Stem
1	meth-	11	undec-
2	eth-	12	dodec-
3	prop-	13	tridec-
4	but-	14	tetradec-
5	pent-	15	pentadec-
6	hex-	16	hexadec-
7	hept-	17	heptadec-
8	oct-	18	octadec-
9	non-	19	nonadec-
10	dec-	20	icos-

Suffix by Functional Group

• Alkane: -ane (propane)
• Alkene: -ene (prop-1-ene)
• Alkyne: -yne (prop-1-yne)
• Alcohol: -ol (propan-1-ol)
• Aldehyde: -al (propanal)
• Ketone: -one (propan-2-one, also known as acetone)
• Carboxylic acid: -oic acid (propanoic acid)
• Amine: -amine (propan-1-amine)

Worked Example

A five-carbon chain (pent-) with a methyl branch at position 2 and a ketone at position 3 becomes 2-methylpentan-3-one. This is the IUPAC-preferred name for the compound commonly referenced in general chemistry textbooks.

Limits of This Calculator

This IUPAC calculator handles straight-chain parents up to 20 carbons, one principal functional group at a time, and methyl plus chloro substituents. It does not do rings, stereochemistry (R/S, E/Z), multiple different functional groups, aromatic ring naming, or IUPAC names from SMILES. For those cases, use a full structure-drawing IUPAC tool such as the ones provided by PubChem or ChemDraw.