Hi Gary,

Where I come from, 20 to 25 is considered healthy. I've also seen some people say 18.5 to 25 (eg this site)

Be aware too, that the upper limit does not apply to people who do much in the way of weight lifting. Muscle weighs more than fat, and you can be quite trim and healthy with a highish BMI, if you are weight lifting.

Cheers.

Rosebud