# Viscosity calculation gmx energy **URL:** \ **Category:** User discussions\ **Created:** [May 4, 2021, 2:51pm UTC](https://gromacs.bioexcel.eu/t/viscosity-calculation-gmx-energy/2093 "2021-05-04T14:51:43Z")\ **Posts on this page:** 1\ **Page:** 1
**Author:** ![kunalmavani](https://avatars.discourse-cdn.com/v4/letter/k/a183cd/32.png) [@kunalmavani](https://gromacs.bioexcel.eu/u/kunalmavani)\ **Post date:** [May 4, 2021, 2:51pm UTC](https://gromacs.bioexcel.eu/t/viscosity-calculation-gmx-energy/2093/1 "2021-05-04T14:51:43Z")
GROMACS version: 2021 GROMACS modification: No Dear All, I am calculating viscosity using gmx energy -vis which uses Einstein’s relation. I’m running the simulation for 200 ns. I am interested in the output files visco.xvg and evisco.xvg. 1. In the visco.xvg I see that I have data till 100 ns and for evisco.xvg till 50 ns. Why is that so and what is the difference? I expected both the files to have equal data points. 2. The shear viscosity data in the visco.avg (54.8 cP) file differs significantly from the last column of the evisco.xvg (192 cP). Data from which file should be referred for shear viscosity? Output from visco.xvg Time (ps) Shear vis (cP) Bulk viscosity 99998 54.864 357.352 99998.2 54.8626 357.348 99998.4 54.861 357.344 99998.6 54.8591 357.34 99998.8 54.8571 357.338 99999 54.8552 357.335 99999.2 54.8537 357.331 99999.4 54.852 357.327 99999.6 54.8503 357.322 99999.8 54.8483 357.32 Output from evico.xvg 49998.5 0.184633 0.304404 0.0879212 0.192319 49998.7 0.18464 0.304396 0.0879256 0.192321 49998.9 0.184656 0.3044 0.0879333 0.19233 49999.1 0.184692 0.304371 0.0879252 0.192329 49999.3 0.18471 0.304369 0.0879221 0.192334 49999.5 0.184667 0.304372 0.0879115 0.192317 49999.7 0.184679 0.304385 0.0879139 0.192326 49999.9 0.184678 0.304385 0.0879119 0.192325 50000.1 0.184678 0.304362 0.087925 0.192321 Thank you very much. Regards, Kunal Mavani