Hello everyone. I have a house rabbit who is 8 and a half, and I wonder how old that makes him in rabbit years.

I seem to find different answers to this on the internet, so does anyone know if there is a definitive human to bunny years answer?

No idea what the definitive answer would be. The breeder I got my angoras from said she had one old buck lived to be 18. That's exceptional though - most live 2 - 4 years. So your's is a good age. I read somewhere that un-neutered/spayed buns frequently develop cancer after age 2 or so, but neutered bunnies can live logner. I dunno how true that is.

I think the average is 7 so anything above that is good going.

Compare that to the average human life span (still three score and ten more or less)

So I'd say 1 rabbit year is 10 human. Never exact though. Especially if talking development - dog years now take into account breed and size and is very complex!!

Admittedly, this from someone who has a mild rabbit phobia due to mother's tales of her childhood psychotic rabbit and seeing a rabbit drop a Cocker Spaniel with one kick.

Rabbits' life expectancy tends to vary according to breed-typicallly, smaller breeds live longer than larger ones. Giant rabbits generally live five or six years at most, dwarf rabbits seven to ten, sometimes older.

Any animal which lives a significantly shorter life than a human will mature very quickly during it's early years.

The old 7 to 1 rule of thumb for dogs has been revised, and it's now thought to be more like 10 to 15 for the first year (depending on breed) - 6/8 for the 2nd year, and 5/6 per year after that.
Smaller dog breeds tending to mature quicker then age slower once they reach adulthood.

Not sure how accurate it is - (my daughter got a rabbit for my granddaughter a coupla years ago) the vet told her 'about' 18 yrs for the first year, then 8 for the 2nd year, then 6 per year after that.
That would put an 8½ year-old rabbit somewhere in it's mid-sixties.

it has been said that an entire female rabbit is in 90% of cases guaranteed to have developed ovarian or uterine cancer by age 5

not sure how true that is but i was told it the year before last in a lecture on animal health, so...