CHINA:
Military K: ~700,000
Military I: ~1,200,000
Civilian:
-Nukes (includes radiation sickness, etc): ~140,000,000
-Conventional Bombing: ~1,000,000
-Famine: ~85,000,000
-Disease: ~15,000,000
-Warlords Fighting: ~10,000,000
-Attemping to Flee: ~1,000,000
-Other: ~1,000,000
Total Chinese Casualties: ~258,500,000 out of ~825,000,000
About ~31.5% of the total population.
Plus, we have migration numbers:
Fleeing to neighboring countries: ~30,000,000
So ~35% total killed. If we add those injured (so much that they can't work or are hampered in those efforts), we could easily reach an even larger reduction in potential workers.
USSR:
Military K: 250,000
Military I: 900,000
Civilian:
-Conventional Bombing: ~50,000
-War Crimes: ~15,000
-Nukes: ~1,000,000
-Other: ~100,000
Total USSR Casualties (not including injured): ~1,400,000 out of ~240,000,000
About ~0.5% of the population.
Even with injuries that is only about 1% that is severely affected.
Total Deaths: ~260,000,000 for the whole war.