I usually upgrade hatchlings to 16qt tubs at around 200 grams. But if theres a snake who is a really picky eater or sensitive in general, I keep them in their current tub for a longer time.
This is my tub to weight ratio:
6 qt - Hatchling
16 qt - 500 grams and smaller
28/32 qt - 500- 2000 grams
41 qt - 2000 + grams and large females
I would also advise to use IRIS tubs. They are easy to replace if you ever need new tubs. Sterilite and Rubbermaid always change their tub styles so it may prove difficult for you to find replacements in the future.
For yearlings and younger, then perhaps a 16 qt or a 28 qt with a divider will be good.