What is the INP file format?
.inp files are associated with Abaqus, a simulation and finite-element analysis software suite maintained by Dassault Systèmes (SIMULIA). They are the primary way to submit analysis jobs to the Abaqus solver.
Files with the .inp extension store the complete input data that defines an Abaqus analysis - geometry, material properties, boundary conditions, and loading steps. They are prepared before a simulation run and submitted to the solver with a command such as abaqus job=model input=model.inp. The solver processes the deck and writes results to an ODB database file for later visualization and post-processing.
An .inp file is plain ASCII text structured around keyword lines that begin with a single * (for example *HEADING, *NODE, *ELEMENT, *MATERIAL, *STEP) followed by data lines; ** starts a comment. Large models can split content across files using the *INCLUDE keyword.
Abaqus was first released in 1978 and is still actively developed. It offers simulation and modeling tools for:
- creating finite-element models for analysis,
- defining material and model properties,
- analyzing model behavior under specific conditions,
- visualizing experimental and analytical data.
Abaqus is used in such industries as automotive manufacturing, aerospace, and industrial production. It is also popular with academia and research institutions.
Security & safety
RISK: LOWAn .inp is plain text and cannot run on its own, so opening one in a text editor is safe. The practical caution is computational, not malware: Abaqus input decks can *INCLUDE other files and reference user subroutines (Fortran/C compiled and run by the solver), so a deck from an untrusted source could point the solver at unexpected files or run custom code - review *INCLUDE and *USER references before submitting an unfamiliar model. Large analyses can also consume significant CPU/RAM. The extension itself carries no exploit.
Format details
in a nutshell- EPANET / SWMM water-network input file - EPA's EPANET and SWMM hydraulic models also use .inp as a plain-text input file - a different domain that shares the extension.
- GIS / generic application input file - Various tools (some GIS, FORTRAN and simulation programs) write generic .inp input files; the Abaqus FEA deck is the dominant technical meaning here.
Programs that open INP files
Windows3 apps
Notepad
Open-source Open the .inp to read/edit the keyword deck as plain text (no solver - viewing/editing only). 
Abaqus/CAE (SIMULIA)
Paid File -> Import -> Model to load the .inp into Abaqus/CAE, or submit it directly: 'abaqus job=model input=model.inp'. 
Visual Studio Code
Free Open the .inp as text to read/edit keywords; community Abaqus-syntax extensions add highlighting. 
macOS2 apps
Visual Studio Code
Free Open and edit the .inp deck as text (Abaqus/CAE itself does not run on macOS). 
Linux2 apps
Abaqus/CAE (SIMULIA)
Paid Import the .inp into Abaqus/CAE or submit with 'abaqus job=model input=model.inp' (Linux is a common Abaqus solver platform).
Vim / VS Code / gedit
Open-source Open the .inp as text to read/edit keywords; pair with the abaqus command to run the job. Technical details
deep spec| File type | Plain-text finite-element analysis (FEA) input deck |
| Character encoding | Plain ASCII (7-bit); UTF-8 compatible but non-ASCII characters are rarely used in practice |
| Keyword syntax | Lines beginning with a single * are keywords (e.g. *HEADING, *NODE, *ELEMENT, *MATERIAL, *STEP); lines beginning with ** are comments |
| File identification | No binary magic bytes; identified by content - file typically opens with a *HEADING keyword block |
| MIME type | text/plain |
| Typical file size | A few KB for simple models; hundreds of MB to several GB for large meshes with millions of nodes/elements |
| Compression | None; files are always uncompressed plain text |
| Nesting / includes | Flat single file by default; external decks can be pulled in via the *INCLUDE keyword |
| Solver invocation | Submitted to the Abaqus solver with: abaqus job=<name> input=<name>.inp |
| Solver output | Solver writes results to an .odb (output database) file; log files use .dat and .msg extensions |
| Platform support | Abaqus/CAE solver runs on Windows and Linux; .inp files can be edited on any OS including macOS |
| User subroutines | Decks can reference Fortran or C user subroutines (e.g. UMAT, VUMAT) via *USER SUBROUTINE; subroutines are compiled and linked at solve time |
| Keyword backward compatibility | Core keyword syntax has been largely stable since the 1978 first release; older decks generally run on current Abaqus versions without modification |
| Security consideration | Untrusted .inp files should be reviewed before submission - *INCLUDE can reference arbitrary file paths, and user subroutines execute native compiled code |
| Released | Abaqus first released 1978 by HKS; the keyword .inp deck has been Abaqus's core input since then |
| Latest version | Tracks the Abaqus release (e.g. Abaqus 2024); keyword syntax is largely stable |
| Specification | help.3ds.com |
INP conversions
Community Q&A
asked by usersNo questions yet - be the first to ask about INP files.
