A webpage is made by CFTRI to convert doses from one species to another including human. It is easy now to use this webpage for dose conversion across the laboratory animal species. the webpage:
https://dosecal.cftri.res.in/index.php
Hope you find it useful to get your answer.
Also please read the following paper if that interest you.
Article A simple practice guide for dose conversion between animals and human
just double the dose : Rat dose conversion factor is approx 6 and for mouse dose conversion factor is 3 ...
Therefore just double the dose. (actually you will be doubling the dose for Mouse but since mouse size is small therefore total drug used will be less. The animals which are small and have higher metabolic rates will get higher per kg doses.
Article A simple practice guide for dose conversion between animals and human
Dear Manoj! Generally speaking, larger animals require smaller drug dose on weight basis, because they have lower metabolic rates. In the case of mice (20 gr), you should double the rat dose. The calculator for other animals is in the articles attached. Good luck!