I am not sure about containers ie. pots that you get from stores but I know a bit about nursery containers. A 1 gal nursery container is about an 6-7 inch diameter pot about 10 " deep. If you need me to I can go and measure whatever size you would want. Nursery containers are not as tapered from top to bottom as pots you buy. Let me know if you need more info
Tim

I don't know any formula or anybody but the easiest way to know is go to any plant nursery store or Home Depot and you will notice their signs 1 gallon plants, 2 1/2 5 gallons 7 1/2 or 15 gallons.
You can also visit the pot area and it will tell you how many gallons a pot is on display.

ben,

i guess that is where my question has come from. i was reading something about how you are no longer supposed to sell plants as gallon sizes, but rather #1 #5 #7 etc to stop some sort of misleading sales tactic distributors and retail stores can have. But to me this makes it even more confusing. For example i bought what home depot is calling on there recipt a 10 gallon orange tree, but i dont think it was actually 10 gallons. Essentially i was told that inorder for my orange tree to be productive in a container, it would have to be in a 15 gallon container. Home depots containers that they sell (ie ceramic pots, decrative plastic pots etc) just say the diamiter of the bottom of it, as they are not straight down top to bottom but have a little bit of a push inwards on the way down.

i am going to home depot again in the next few minutes to see if i can figure any of this out.

Another way to figure out (approximately and the way I do it) is to measure it myself.
I get me a 1 plastic gallon (milk) and if I want to know how many gallons a pot is, I covered all the holes wiith duct tape and fill the pot a gallon at a time. IE when I want to know how many gallons a half wine barrel- that's what I did.
The #1 or #10 pot- that, I don't know anything about. It sure is confusing.
I just transplant my plants to the next bigger pot.
I am not sure why do you want to know exacly how many gallons a pot should be. You got me lost there.

ben,

i was told that a 15 gallon container is the size i will need to grow a citrus tree in for it to do well. problem is i dont know how large that is compared to the container its in now.

Nero:
What they are saying is not probably true from my own experience. I have many citrus trees that are giving me lots of fruits on 5, 7 1/2 gal, 10 gallons all the way to 25 gallons.
It depends on how big is your tree.
Let me give you an advice as to the right pot you need for your tree.
If your tree is in 1 gallon pot transfer your tree to the next pot bigger maybe 2 or 2 1/2 gallon. Don't jump to a 15 gallon pot right away because your plant will encounter lots of problem. Transferring to a much larger pot is detrimental to your tree because the root of your tree lies on the almost on very top of the soil and the soil under the roots will remain soggy because there is no activity going on there. evaporation only takes place for a very few inches on top of your soil. What remains under there is there will be an accumulation of unaerobiic bacteria which will be toxic to your plants.
A good rule of thumb is to transfer your plant to a pot which is 1 to 2 inches bigger diameter of your original pot.
The deeper the pot the better is for your plant because the water table will be deeper so the roots will remain constant moist but not soggy.
I'll post pic of my plants here soon.
So the actual size or gallon size is immaterial I think but if you want to really know, cover the holes of your pot with tape, filled it with water and measure th content in agiven known gallon size like a gallon milk carton.
Eventually you will reach the 15 gallon pot the plant dealer is talking about. That depends how biig is your plant.

This pics are on
5 gal
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25 gal- wine barrel

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5 gallon

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5 to 7 ½ gal

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ben, thanks for posting the pictures.

i purchased what home depot was calling a 10 gallon tree that i placed into a slightly larger pot. So I believe that I am good with the current pot size, I guess I am just curious with as to wether it will be a necessity to repot at sometime. I have heard that the containers dwarf the tree, so i would assume that you could leave them in a pot that was not that extensive and have them still produce. Your trees look like they are producing quite well.

You can leave your plant in a container for a while. Until the roots get root bound. Transfer it before it gets to that. I'd say a maximum of 3 years. The soil lose its propeties and the tree goes downhill after that time due to compacted soil, etc... even though you are giving them the right fertilizer and getting rid of the salts in the soil right on schedule.

can you just replace soil or do the roots wrap themselves all up in them that you have to go to a large container to add more soil?

That's an interesting question. I never thought of it that way. I always change my pot to a size bigger because I want my citrus to grow bigger so I can have more fruits. But I guess you can do it your way. It's your tree. I guess if you don't want your tree grow big that's one way of doing it. Like bonzai trees. But what's the use of replacing the soil if you don't want your tree roots to expand? Citrus likes to have their roots crowded in the pot but not compacted and tangled around and around the pot. But again why not?
Do it your way.
I've been experimenting with my citrus trees and that's the fun of it all. Just don't do whatever someone tells you to do. It's your tree. You can do anyway you want.

I quit trying to figure out container capacity ,now I use the following calculator. Just enter the dimensions and you have what you want.
Karl

http://grapevine.abe.msstate.edu/~fto/tools/vol/index.html

Karl,

I tried that and it gave me a number it says for volume, but what unit of measurement is that?