Most estimates put Russian casualties at 200,000. The initial partial mobilization sent an estimated 20k of age men fleeing to other countries. They have cleaned out their jails to fill Wagner ranks. With longer range weapons and expertise, Russians supply lines are getting much longer.
Ukraine has to be getting thin on manpower but they are the defender at this point and they have shorter supply lines and the backing of the most of the free world. I would think they have some fallback plans in place to bait the Russians a bit but I'm just a guy on the internet.