Pot sizes and when to transplant?

I have germinated my seeds placed them in seedling trays and have grow they have been in there about a week. When do I transplant to a bigger pot and what size/litre should I go too?

Transplant now .
Solo cup, 1 gal, 3 gal, 5 gal etc. Normally I do this about every 2- 3 weeks, dependent on growth.

When my seedling just looks too big for the pot or I see a root coming out of the bottom I transplant. I try to only transplant twice during the plant life span. I use 5 gallon smart pots as the final home. I grow auto's due to ease and 5 gallon Smart fabric pots are what my plants spend over half their life in. I did use a 7 gallon smart pot one time and got a hell of a yield but that fucker took up too much realestate.

I put seeds in 5 gallon pots.
Plants do not like to be transplanted and I am lazy.

You can grow plants in 16 ounce cans if you want, it is all up to you and what you want to do.

I would never transplant more than once. Some will disagree, but I've never seen any scientific evidence that transplanting every 2 weeks for 3 months does anything positive for a plant. Others will say otherwise, but the majority of people would never even consider transplanting, at the most, twice. Most people transplant once. Some never transplant. Just do whatever makes you happy.

i go red cup, 3gal then 5. sometimes i start in 3gal then 5 if im wanting to haul ass. its up to u tho

I go solo then 7 gal. I usually have a few months before I flower so its enough time to let the plant root bound again.