GRO (GROMACS structure file)

Coordinate reader


Coordinate writer


Topology parser


GRO files provide topology, coordinate, and sometimes velocity information.

Reading in

Prior to MDAnalysis version 0.21.0 and GROMACS 2019.5, MDAnalysis failed to parse GRO files with box sizes where an axis length was longer than 10 characters.


A Universe created with a GRO file and a Universe created with a corresponding TPR file will have different atom and residue numbering, due to how a TPR file is parsed. This behaviour will change in 2.0.0 where TPR parsing will be made consistent with the other file formats.

Writing out

AtomGroups can be written out to a GRO file. However, this format does not support multi-frame trajectories.