When to get a larger enclosure?

Is there a general weight or length that indicates when to get a bigger enclosure? My girl is about 300 grams and about 2 1/2-3ft long now and in a 20G long tank. I don't believe she's out grown this enclosure yet
Thanks

Ive been told ur enclosur length should be 2/3 ur snakes.

Yeah I've heard the tank should be big enough for the snake to be able to stretch out along 2 sides (ex: side and front). I've also heard 2/3. I've also heard a 20L is enough for a full grown BP. There might not be a cemented answer on that. Personally, I got a 40 gal (from a 20L) just because petco was having their $1/gal sale and I couldn't help myself. If the husbandry is right and the snake seems comfortable, he may be fine in his current setup. If you find he is a little cramped, then that may be a sign too. Wish I could offer a more solidified answer but good luck!

The problem with a 20 gallon isn't the length so much as the width. I like to use something wider. (40 qt tubs for me.) But for the small snake you have it's plenty big. :D

Id say ur fine for at least another year then switch over to a 40 breeder if ur gonna keep it as a show snake.

Thanks all. I think she is comfortable in there for now. Just trying to plan ahead-she's growing so fast : )