At how many grams upsize tank?

Hi
Looked through the stickies, and couldn't find the exact info. I am wondering at what weight should I upgrade my tank from a 20 gallon to a 40 gallon?

Mine is only 3 months old, he's growing fast though and is somewhere around 300-320 grams probably.

Probably have some way to go before its time, just want to be prepared for when :)

I would not consider putting a male in a 40 gallons until he reaches at least 1000 grams.

Great! Looks like he have ways to go still! Thanks for the response!