How many liters a rat has a year?

Answer 1

Female rats can get pregnant, generally, from 5 weeks old onwards.

If they are left to have back to back litters (get pregnant, give birth, mate with a male within a few hours of birthing), then they will have 1 litter every 19-25 days, so there being 395 days in a year, that gives you as many as 20 litters per year.

As for male rats, it would depend how many females they managed to get pregnant, for example if a male got 5 girls pregnent, you just go 20 x 5 = 100.