when do you get a bigger tank?

i have had my bp for a month now.he is in a 10 gallon tank and hes about 2 feet long maybe a little less but i was thinking about putting together a 20 gallon for him.do you think it will be a problem he has eaten all 4 times i have had him and doesnt get spooked when i hold him basically for 5 minutes everyday i can.i think he will be fine but this is my first one so im not too sure thanks

from how ive gone about it and talked to other people about when the snake is the length of the diagonal its time to upgrade

thanks ill try that out