Container Size

I am curently in my 2nd week of flowering and have my plants
(18-24 in) in soil in containers about 6 in high, I am not sure exact volume. At what point if ever should I repot and if I do what size container should I go to? Thanks in advance.

1 gallon of dirt for every foot of plant im over this rule now and its growing awsome im going to try to do the whole grow in this pot good luck here is a pic. ps dont spry your plants it washis away the crystals.

Thanks for the pic I definitly need to re-pot, my plants are a little smaller and in pots 1/2 the size of that one!

yeah I have tried all different sizes and shapes and I like the black like i think they are 4-5 galllon planters from like nurseries.

good luck and when you transplant get some superthrive to help avoid shock..........