SMILES to InChI Converter
In short: Convert SMILES strings to standard InChI identifiers for database and publication workflows. It is free, works in your web browser and needs no download.
Convert SMILES to standard InChI for search, indexing, and publication workflows.
Input and output formats
| Input: SMILES | Output: InChI | |
|---|---|---|
| Full name | SMILES (Simplified Molecular Input Line Entry System) | InChI (IUPAC International Chemical Identifier) |
| What it holds | Atoms, bonds, rings, charges and stereo as one line of text. No coordinates. | A layered text identifier built from the structure. The standard InChI is the same in every program. |
| File or form | .smi or plain text | Text starting with InChI=1S/ |
File Format Explained
SMILES is a compact line notation for molecular connectivity. It is convenient for drawing tools, search boxes, and scripts.
InChI is the IUPAC International Chemical Identifier. It is a layered, standardized identifier designed for chemical database exchange, indexing, and comparison.
Use SMILES when you need an editable structure string. Use InChI when you need a standardized identifier that is less dependent on a specific SMILES canonicalization style.
Example and reading the output
Aspirin's SMILES CC(=O)OC1=CC=CC=C1C(=O)O converts to:
InChI=1S/C9H8O4/c1-6(10)13-8-5-3-2-4-7(8)9(11)12/h2-5H,1H3,(H,11,12)
1S: version 1, standard InChI.C9H8O4: the molecular formula layer./c…: the connectivity layer, using InChI's own atom numbering./h…: where the hydrogens sit; the brackets mark a mobile hydrogen shared between the two carboxylic acid oxygens.
Why the same molecule always gives the same InChI
Several different SMILES can describe aspirin, depending on which atom you start from. Standard InChI is canonical, so all of them produce the identical string above. This makes InChI a good choice for comparing structures and checking duplicates.
FAQ
Is stereochemistry included? Yes. @ and @@ in SMILES become /t, /m and /s layers in the InChI. Need something shorter? Use SMILES to InChIKey.
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