Sorry, I wouldn't know either. You might try posting on an Australorps thread. Do a search for them? I know they wouldn't be as large as a Jersey Giant - and don't believe they are regarded as large birds.
I keep Australorps, however I have never measured how tall they stand. They are a large breed and must stand about 20 inches tall. Some are shorter or taller than others. They are definitely a wonderful breed to keep.