InChI to InChIKey Converter
InChI is long and not index-friendly. The InChIKey is a fixed 27-character hash of the same structure — perfect for databases, URLs and search.
InChIKey vs InChI
The InChIKey is a hash of the InChI. The first 14 characters encode the molecular skeleton and the next 8 encode stereochemistry, charge and isotope layers, with a final check character. Because it is always 27 characters, it fits neatly into a database column and a URL.
Where InChIKeys are used
- PubChem, ChEMBL and Wikidata — all index compounds by InChIKey.
- Structure search — paste a key into a database to jump straight to a compound.
- Primary keys — stable, case-sensitive identifiers for a local registry.
Important limitation
InChIKey is a one-way hash. You cannot recover the structure from it. Always keep the InChI or the original structure file alongside the key.