When/how do you repot?

What are you growing? I hope it's not an autoflower as they hate to be transplanted except by a master gardener... and even then they can react badly. If it's a photo, then you are looking at what size root ball you have... the larger the better - and if roots are actually coming out of the bottom of your pot, it's definitely time.. Good luck!

One of the easiest ways to tell that a plant needs repotting is to check and see if the roots are growing out of the drainage hole of the pot. If so, this is an indication that the roots have run out of room and your plant needs a larger pot. Another could be that the plant is growing much slower than normal

SEvere symptoms -- Plant stops growing anymore. Highly sensitive to nutrient issues even if good ratio and concentration is provided. So, you'll start getting leaf symptoms and virtually nothing you can do to fix it except re-pot it. The roots will be wrapping around and around and eventually strangulate itself in some ways. That's a visual clue you can see occurring. some wrapping is "okay" but will eventually be an issue if extreme. Less severe - vertical height stops before all of that. how ofter are you irrigating? if 1 or more times per day that's a really good sign you want a bigger pot. (unless in some advanced technique multi-fertigation per day setup) The frequency isn't necessary bad, but the effort is much more than necessary for a happy plant. Don't tranplant with a bone-dry substrate. it'll fall apart more easily. So, i like to do it when still fairly moist, cause it will hold together better as i do things. I pull/squish rim gently to get sides of pot to separate from sides a bit, if snuggly in there. I press gently on bottom of pot to try to get it loose from sides of pot, too. All of this is so it slides out more easily... gently pulling at base of trunk, pushing bottom of pot slightly etc etc.. once it starts to slide, it's easy as pie. if roots are bunched up at bottom (root bound) i'll caefulyl spread it out slightly -- very little effort with little concern for how well it is spread out. more of just running fingers across it so it loosens upa bit.. don't want to be ripping/tearing roots at all.. so only if extreme do i do this. Otherwise, i simply plop it into a partially filled new pot and fill around it. Then irrigate to help settle the substrate into itselft... make sure there are no large air pockets etc.. if i have to add a bit more on top it's all out and ready to do so. Tamp it down right and it isn't necessary. If careful, transplant shock should not happen very often, but can. I rarely see a plant stall after transplant. Probably cause i don't agitate the root ball too much. As soon as i think the rootball and roots can hold the chunk of substrate during this process, it's usually ready to transplant long before any rootbound issues and rarely do anything involving spreading roots out. If substrate and rootball falls apart and become loose, expect a stoppage of growth after transplant. It'll probably live, but it's gonna be focusing on re-creating that rootball for a while. When canopy is same size as a smaller pot, this is another good queue to transplant.