Extract text from Gaussian checkpoint files (FCHK)
To convert FCHK checkpoints to another format, you need Gaussian or other Data software.
To convert other file formats to the "Computational Chemistry Output" file type, you need software like Gaussian or a similar tool.
The .fchk file is a Gaussian Formatted Checkpoint file used by Gaussian, a premier computational chemistry software package. These files contain human-readable ASCII text representing quantum mechanical calculations, including molecular geometries, molecular orbitals, basis sets, and electron densities. Unlike the binary chk format, .fchk is text-based to allow safe transfer between different computer operating systems and hardware architectures.
The main disadvantage of the .fchk format is its massive, cumbersome size and highly specialized structure. Because it relies on uncompressed text to map vast mathematical matrices, files routinely exceed hundreds of megabytes. It is heavily tied to the Gaussian ecosystem, meaning you cannot easily preview the 3D structures on a standard computer. Users frequently need to convert .fchk files to standard coordinate formats like XYZ or PDB for simple molecular viewing, or to CUBE files for rendering electron density in universal 3D chemistry tools.
Because the .fchk is a proprietary output from complex quantum calculations, standard online document or image converters will fail to process it. Only specialized computational chemistry utilities can correctly parse these complex numerical matrices. Just drag and drop your file to identify the format, view it, and convert it when possible. If our analysis detects standard structural data, convert.guru will help you view the raw text or attempt a conversion.
Convert.Guru analyzes your FCHK file, detects the exact format, and lets you read the text inside.
Users also converted GJF, PTS, TST and CHK files.
If you want to convert FCHK file to CHK, CSV, JSON, XML, YAML, YML, TOML, INI, CFG, CONF, DAT or DB, you can use Gaussian or similar software from the "Quantum Chemistry Data Storage" category. In the File menu, look for Save As… or Export….
To convert DBF, XML, SQLITE, XLSX, SQL, TSV, ACCDB, YAML, MDB, CSV, ODS or JSON files to FCHK, try Gaussian or another comparable tool in the "Quantum Chemistry Data Storage" category.
The history of Convert.Guru began over 25 years ago in California with Tom Simondi’s file-format database. A former contributor to Space Shuttle development and a software pioneer of the 1980s, Simondi established a trusted resource for file type analysis that was even referenced by Microsoft Windows XP. Today, we use modern technology to process and convert thousands of file formats while continually improving our FCHK converter.