Molar mass of organic compounds

Organic compounds are built on chains and rings of carbon atoms. Their formulas are longer, so a careful atom count matters most here.

Organic formulas are often written to show structure, as in CH3COOH or C2H5OH. Add up each element across the whole formula before you start. Different compounds can share one molecular formula (isomers) and so one molar mass, and many share an empirical formula: glucose, acetic acid, lactic acid and formaldehyde are all CH2O in the simplest ratio.

This page lists 25 organic compounds with their formulas and molar masses, lightest first. The lightest here is ethyne at 26.04 g/mol and the heaviest is sucrose at 342.30 g/mol. Tap a name for the full working, the percentage of each element and worked examples.

Which values? This site uses the abridged standard atomic weights published by IUPAC (CIAAW), read on 12 November 2026. Your textbook or question paper may round them differently, for example H = 1 and O = 16, so its answer can differ slightly. In an exam, use the values the paper gives.

Not in the list?

Type any formula into the calculator. It handles brackets and water of crystallisation and shows the same working as these pages. The method by hand is on the step by step page.

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