Width/Length of the containers? 25 gallon containers come in all sorts of shapes and sizes.

Gallon size isn't all that important since they only need about 12" of depth. But you should be able to evenly space several plants 8-10" apart or around the container somehow.

For example, 10 gallon grow bags made for potatoes call for 3-4 plants. They are 12-14" deep and 22" wide side to side. That assumes careful watering and extra feedings.

Dave

I think my totes last year were 18 gallons. I put 3 seed potatoes in each of them. I ran out of potting soil and one was full about 8" the other....let me think...12-18" maybe? Anyways....

I got bored of watering them and dumped them all out in early July (I still had my main, in-ground potatoes anyways). I was surprised to get a meal or two's worth of new potatoes. If they had stayed in those buckets for the rest of the summer, I would have gotten a pretty good harvest out of them I think.