What age do cats reach their full adult weight?

I was wondering if anyone knows at what age (average) neutered male cats reach their adult weight? I have 12-month-old littermates (DSH) and I am wondering if they will gain any weight... I wanted to enroll them in this pet blood donor program but they have to be 10 pounds and two of them are just under that...

I think it all depends on the cat. Some breeds grow for much longer than others. My boys are 2 and 2 1/2 and seem to have just recently stopped growing.

I think it's different from cat to cat, because one of my cats just kinda stopped growing (thank god, he's tall and gangly) and he's around 2, and one of my other cats never grew any bigger than when I got her. I got her when she was around a year old, maybe less, and she is pretty much the exact same size now as she was then. She'll be 2 in September (est. b-day)

Definitely based on the breed - Maine Coons can often reach their full size between ages 3 and 4.

depends on the cat... My smallest girl is 8.5-9 lbs and did not stop till about 36-40 months ... My 2 yr old boys were 13.5 and 14 at 15 months ...

They don't have a breed, they are DSH cats (feral rescues.)

I know about Maine Coons, I have one and she is still growing at 2.5 years old, but my 1 year old cats are just regular 'alley cats'. One of them is 13.5 pounds but the others are under 10 pounds.

It depends on the breed.... Ragdolls for example by 4 years old...