Here's some good info I've kept around on pot size and a few other facts from a FAQ online... This is good info although changing pots as much as suggested depends mostly on how big you want to flower your girls at and many other factors such as the available grow space and strain. I put my rooted clones into one gallon Agroliner grow bags and veg them for about 3 weeks and then I transplant them into 7 gal containers for another couple of weeks of veg and then flowering. This time around I'm trying something a bit different. I'm growing 4 Afghani Mazar indica girls using 10 gal pots with two plants in each pot. I lollipop pruned all of them so each has four branches and flowered them at around 14" and so far it's working out well. I tend to prefer my gals BEEFY but many others prefer to fill up their bloom space with much smaller clones in smaller pots... Different strokes for different folks...
A good rule of thumb is 12" of height/per gallon and to double the size of your existing pot on transplanting. Other factors involved in determining pot size are your grow room footprint size, the amount/intensity of light plants receive, where plants are in the grow cycle and if the are from seed or clones.
Grow room area size: If your grow room foot print size is small and horizontal space is at a minimum then BOG's (Bushy Older Grower) doubling potting method is a good alternative. Rather than repotting into a larger diameter pot your existing pot is set on top of another pot a few inches more in diameter. Thus giving your plants a lot more vertical root volume of soil to grow into and less horizontal volume.
Amount of light and intensity: Plants that are under low wattage lights (70-250) tend not to grow as big and as quick as plants under high wattage lights (400-100), thus one can scale back pot size slightly. Also if your plants are under a 24/0 cycle or an 18/6 cycle this will affect growth rates and repotting sizes.
Growth cycle: The average grower will find that they must repot usually every 2 weeks while in the veg cycle. Going from a 1-1.5 gallon to a 2-3 gallon in the third/fourth week of the veg cycle. From a 2-3 gallon pot to a 4-5 gallon in the 5-6 week of the veg cycle. Note it is always best to repot 1-2 weeks before you flip your lights to the 12/12 flowering cycle and to let your plants finish off in that last transplanted pot size.
Seed or clones: This will make the biggest difference between pot sizes. Since one must veg up to 4-6 week from seed to reach plant maturity. Cloned plants need not be veg as long 1-3 weeks. This will drastically reduced the pot size needed for a cloned plant.
These guide lines are by no means written in stone, all environments are different and will produce different growth/repotting rates this is just a basic outline.