How old are rabbits in rabbit years if they are one in human years?

One answer: 45 years.

Another answer: Domestic rabbits live on average 10 years, but they can live up to 16, 17. If an average human's lifespan is 70, but we can live up to, say, 110, 120, then... I'd estimate that a 5-year old rabbit is 35 years old.