What an InChI is made ofStep 1 of 17 of the InChI walkthrough. An InChI is a prologue followed by layers, each introduced by a slash and a letter. Ethanol needs only the three main layers: the formula, the /c connections, and the /h hydrogens. Layers always appear in a fixed order and any layer a structure does not need is simply absent, so a short InChI is not an incomplete one. Every layer after the formula refers to atoms by their canonical numbering, which is why deriving that numbering is most of the work.It opens on CCO, drawn live, so the layer under discussion changes as you change the structure.Convert a structure to its InChI and InChIKey and back, convert a whole CSV, XLSX or SDF file, learn how the identifier is derived, and practise writing its layers. The InChI engine is WebAssembly running in your browser, so the tool needs JavaScript — and nothing you open ever leaves your machine.

Convert — a structure in, an InChI out

Batch — a whole CSV, XLSX or SDF file

Tutorial — how an InChI is derived

Exercises — write the layers yourself

Cheatsheet — every layer in a table

Tests — the IUPAC regression corpora

Download — take the engine away

About, and what to cite

Our other tools

learn.cheminfo.org — Arrange the tools into a course and hand out its link.

vcl.cheminfo.org — Combine a core and fragments into a screened library.

smiles.cheminfo.org — Draw a structure, read its SMILES, learn the notation.

iupac-name.cheminfo.org — The IUPAC name of a structure, and the structure a name denotes.

openbabel.cheminfo.org — Convert a structure between any pair of chemical file formats.

www.chemcalc.org — Molecular formula, exact mass and isotopic distribution.

dbe.cheminfo.org — Count rings and double bonds from a formula or a structure.

www.nmrium.org — Process and assign NMR spectra in the browser.

metabo.nmrium.com — Turn a batch of NMR spectra into a map of your samples.

derepflow.cheminfo.org — Identify the constituents of a mixture from its ¹³C spectrum.

surge.cheminfo.org — Every constitutional isomer of a molecular formula.

tex.cheminfo.org — LaTeX formulas rendered to SVG or PNG from a URL.

lcao.cheminfo.org — Combine atomic orbitals into molecular ones.

regexp.cheminfo.org — Learn regular expressions in a live playground.

pdb.cheminfo.org — A fast look at any Protein Data Bank entry.

elucidation.cheminfo.org — A structure from a 1H NMR spectrum and a formula.

equilibrium.cheminfo.org — Chemical equilibria: pH, speciation and titration curves.

polycarp.cheminfo.org — Predict the microstructure of a radical copolymerisation.

3d.cheminfo.org — Conformers in 3D from a structure you draw.

periodic-table.cheminfo.org — The periodic table, coloured, plotted and taken apart.

database.cheminfo.org — Query a real chemical dataset in SQL and in Mango.

symmetry.cheminfo.org — Find the symmetry of a molecule, a crystal or a pattern.

osiris.cheminfo.org — Predicted toxicity risks and properties, one molecule or many.

atoms.cheminfo.org — Electrons, neutrons, Lewis structures and oxidation states.

moles.cheminfo.org — Balance a reaction, and work out its mass composition.

inorganic.cheminfo.org — Name an inorganic compound, and write its formula.

powerpoint.cheminfo.org — Put a live tool on a slide, from the link its Share button gives.