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obabel(1) General Commands Manual (urm) obabel(1)


obabela converter for chemistry and molecular modeling data files


obabel [-H help-options]

obabel [OPTIONS] [-i input-type | -: "SMILES-string"] infile [-o output-type] -O outfile


obabel is a cross-platform program designed to interconvert between many file formats used in molecular modeling and computational chemistry and related areas.

Open Babel is also a complete programmers toolkit for developing chemistry software. For more information, se the Open Babel web pages <>.


If only input and output files are given, Open Babel will guess the file type from the filename extension.

-: "SMILES-string"
Enter SMILES string and use it in place of an input file. The SMILES string should be enclosed in quotation marks. More than one can be used, and a molecule title can be included if enclosed in quotes.
Format-specific input options. See -H format-ID for options allowed by a particular format
Append text to the current molecule title
Append the molecular formula after the current molecule title
Convert dative bonds: e.g., [N+]([O-])=O to N(=O)=O
Center atomic coordinates at (0,0,0)
Combine molecules in first file with others having the same name
Continue after errors
Delete Hydrogens
Filter the level of errors and warnings displayed:
1 = critical errors only
2 = include warnings too (default)
3 = include informational messages too
4 = include "audit log" messages of changes to data
5 = include debugging messages too
For multiple entry input, start import with molecule # as the first entry
Output the available fingerprint types
Add hydrogens
Output usage information
Output formatting information and options for format specified
Output formatting information and options for all formats
Specifies input format, see below for the available formats
Join all input molecules into a single output molecule entry
Translate computational chemistry modeling keywords (e.g., GAMESS and Gaussian)
Produce multiple output files, to allow:
  • Splitting one input file - put each molecule into consecutively numbered output files
  • Batch conversion - convert each of multiple input files into a specified output format
For multiple entry input, stop import with molecule # as the last entry
Specifies output format, see below for the available formats
Specify the output file. This option applies to obabel only.
Add Hydrogens appropriate for pH (use transforms in phmodel.txt)
Add or replace a property (e.g., in an MDL SD file)
Convert only molecules matching the SMARTS pattern specified
Separate disconnected fragments into individual molecular records
All input files describe a single molecule
Add or replace molecular title
Format-specific output options. See -H format-ID for options allowed by a particular format
Convert only molecules NOT matching SMARTS pattern specified
Output version number and exit
Compress the output with gzip


The following formats are currently supported by Open Babel:

  • acr -- Carine ASCI Crystal
  • alc -- Alchemy format
  • arc -- Accelrys/MSI Biosym/Insight II CAR format [Read-only]
  • bgf -- MSI BGF format
  • box -- Dock 3.5 Box format
  • bs -- Ball and Stick format
  • c3d1 -- Chem3D Cartesian 1 format
  • c3d2 -- Chem3D Cartesian 2 format
  • caccrt -- Cacao Cartesian format
  • cache -- CAChe MolStruct format [Write-only]
  • cacint -- Cacao Internal format [Write-only]
  • can -- Canonical SMILES format
  • car -- Accelrys/MSI Biosym/Insight II CAR format [Read-only]
  • ccc -- CCC format [Read-only]
  • cdx -- ChemDraw binary format [Read-only]
  • cdxml -- ChemDraw CDXML format
  • cht -- Chemtool format [Write-only]
  • cif -- Crystallographic Information File
  • cml -- Chemical Markup Language
  • cmlr -- CML Reaction format
  • com -- Gaussian Cartesian Input [Write-only]
  • copy -- Copies raw text [Write-only]
  • crk2d -- Chemical Resource Kit 2D diagram format
  • crk3d -- Chemical Resource Kit 3D format
  • csr -- Accelrys/MSI Quanta CSR format [Write-only]
  • cssr -- CSD CSSR format [Write-only]
  • ct -- ChemDraw Connection Table format
  • dmol -- DMol3 coordinates format
  • ent -- Protein Data Bank format
  • fa -- FASTA format [Write-only]
  • fasta -- FASTA format [Write-only]
  • fch -- Gaussian formatted checkpoint file format [Read-only]
  • fchk -- Gaussian formatted checkpoint file format [Read-only]
  • fck -- Gaussian formatted checkpoint file format [Read-only]
  • feat -- Feature format
  • fh -- Fenske-Hall Z-Matrix format [Write-only]
  • fix -- SMILES FIX format [Write-only]
  • fpt -- Fingerprint format [Write-only]
  • fract -- Free Form Fractional format
  • fs -- Open Babel FastSearching database
  • fsa -- FASTA format [Write-only]
  • g03 -- Gaussian 98/03 Output [Read-only]
  • g98 -- Gaussian 98/03 Output [Read-only]
  • gam -- GAMESS Output [Read-only]
  • gamin -- GAMESS Input [Write-only]
  • gamout -- GAMESS Output [Read-only]
  • gau -- Gaussian Cartesian Input [Write-only]
  • gjc -- Gaussian Cartesian Input [Write-only]
  • gjf -- Gaussian Cartesian Input [Write-only]
  • gpr -- Ghemical format
  • gr96 -- GROMOS96 format [Write-only]
  • gzmat -- Gaussian Z-Matrix Input
  • hin -- HyperChem HIN format
  • inchi -- IUPAC InChI [Write-only]
  • inp -- GAMESS Input [Write-only]
  • ins -- ShelX format [Read-only]
  • jin -- Jaguar input format [Write-only]
  • jout -- Jaguar output format [Read-only]
  • mdl -- MDL MOL format
  • mmd -- MacroModel format
  • mmod -- MacroModel format
  • mol -- MDL MOL format
  • mol2 -- Sybyl Mol2 format
  • molreport -- Open Babel molecule report [Write-only]
  • moo -- MOPAC Output format [Read-only]
  • mop -- MOPAC Cartesian format
  • mopcrt -- MOPAC Cartesian format
  • mopin -- MOPAC Internal
  • mopout -- MOPAC Output format [Read-only]
  • mpc -- MOPAC Cartesian format
  • mpd -- Sybyl descriptor format [Write-only]
  • mpqc -- MPQC output format [Read-only]
  • mpqcin -- MPQC simplified input format [Write-only]
  • nw -- NWChem input format [Write-only]
  • nwo -- NWChem output format [Read-only]
  • pc -- PubChem format [Read-only]
  • pcm -- PCModel format
  • pdb -- Protein Data Bank format
  • pov -- POV-Ray input format [Write-only]
  • pqs -- Parallel Quantum Solutions format
  • prep -- Amber Prep format [Read-only]
  • qcin -- Q-Chem input format [Write-only]
  • qcout -- Q-Chem output format [Read-only]
  • report -- Open Babel report format [Write-only]
  • res -- ShelX format [Read-only]
  • rxn -- MDL RXN format
  • sd -- MDL MOL format
  • sdf -- MDL MOL format
  • smi -- SMILES format
  • sy2 -- Sybyl Mol2 format
  • tdd -- Thermo format
  • test -- Test format [Write-only]
  • therm -- Thermo format
  • tmol -- TurboMole Coordinate format
  • txyz -- Tinker MM2 format [Write-only]
  • unixyz -- UniChem XYZ format
  • vmol -- ViewMol format
  • xed -- XED format [Write-only]
  • xml -- General XML format [Read-only]
  • xyz -- XYZ cartesian coordinates format
  • yob -- YOB format
  • zin -- ZINDO input format [Write-only]


Individual file formats may have additional formatting options.

Input format options are preceded by 'a', e.g. -as

Output format options are preceded by 'x', e.g. -xn

For further specific information and options, use -H<format-type>
e.g., -Hcml


Standard conversion:

obabel -Oethanol.pdb
Conversion from a SMI file in STDIN to a Mol2 file written to STDOUT:
obabel -ismi -omol2
Split a multi-molecule file into new1.smi, new2.smi, etc.:
obabel infile.mol -Onew.smi -m


obenergy(1), obfit(1), obgrep(1), obminimize(1), obprop(1), obrotate(1), obrotamer(1). The web pages for Open Babel can be found at: <>


A cast of many, including the currrent maintainers Geoff Hutchison, Chris Morley, Michael Banck, and innumerable others who have contributed fixes and additions. For more contributors to Open Babel, see <>


Copyright (C) 1998-2001 by OpenEye Scientific Software, Inc.
Some portions Copyright (C) 2001-2007 by Geoffrey R. Hutchison

This program is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation version 2 of the License.

This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.

October 10, 2019 Open Babel 3.1