i have a lovely bitch bullmastiff, but would like to know how old do they stop growing she is 12 months old now,
and would just like to know.

It said in my book that they are not fully mature until the age of three. Height wise i would imagine that to be 12 months and then they start filling out.

hi
i have three bullmastiffs..and all have been slightly different :>)

rule of thumb is that most will have reached their full height by 12 months ...though one of mine grew a further 2 inches between 11 months and 14 months !!!!
as for fully mature ...it all depends on your line ...but three years old is the about the norm
don't worry too much about size ...the leaner the better as they grow ...your dog will make its full potential size in it's own time ..patience is the key
warm regards
debbie