Best container sizes for me, are 30-45 gallon. The bigger the container, will yield to a higher percentage of crop production. Keep in mind, those big containers will weight a lot, so chose a container size depending on your strength.

Navid.

i asked the same question some time ago. was told 20 gal or larger. my final size is 10 gal. this provides enough for me.

How about the pruning? How do you keep it small and still get a crop?

Louborges,
I have been able to get 5-6 dozen figs on many 2 year old plants in 5 gallon buckets by simply pruning the young tree. My largest size will be 20 gallon SIPs (made from 30 gallon barrels) similar in size to the Bill's SIPs.
  
 
Here's a picture from Bill's Figs in NJ which shows a few 3 year old trees that have been pruned to the container tree form. Bill Muzychko wrote

Young people might like 20-30 gal pots but for older folks 5-10 gal will get plenty of fruit. I weighed a 15 gal once at 125 lbs. Moving is difficult and repotting nearly impossible for seniors. I've gotten 40 figs off a second year plant in a 3 gal pot. What's not to like about that?

The other thing is the more vigor the plant has the less it will yield in proportion to it's size. So a larger pot can be self defeating by causing more vigor and a less fruitful condition. I planted a 3 gal plant in the ground in my greenhouse. It grew 8ft branches in all directions. But I harvested less fruit off that sprawling giant than the year before off a 3 gal pot. It's going back into no bigger than 12 gal. Only going that big because the plant is now so much bigger.

I've put 3 varieties in a 12 gal and gotten maybe 80-100 figs total. Total 6 varieties in two pots. All varieties produced each year.

Wow! Thanks so much for the info and the great picture.

Navid, how do you move those containers around?

I asked my brother about what can help keep the weight down on these big containers. He said Leaves, I said why don't I just put Feathers....LOL.....I told him that leaves can get moldy and affect the roots. I am going to look for something close to 10 gallons or just not add so much heavy soil to the container....yeah I came close to messin up my back putting them in the washroom for winter.

you guys have heard of Dolly I hope, LOL
there are retractable types that the bottoms get longer or shorter depending how you want to use them.

Bob, I use a heavy duty dolly to move those containers around.

I settled on planting my trees into 18-gallon, rectangular storage tubs that can be bought in any Big Box Store, like, Home Depot.  "RUBBERMAID" is a good quality, but the cheapo brands work just as well.  I pay less than $9.00.  I then drill a few 3/4" drainage-holes near the bottom, but only on the sides....and, on all four sides of the tubs.  I fill the tubs with nice fresh modified 5:1:1:1 mix, and plant the trees. 

I have one older tree growing in this kind of converted storage tub, that now has a 4" diameter trunk, and is about 5-1/2 ft. high including all the fig-producing, branches.  It's a little heavy when watered, by I move it around with a 4-wheel dolly.

Why 18-gallons?  Easy to find....easy to move...holds about 15+ gallons of mix - (don't forget to leave space for watering) .... they're cheap, and will last a long time.  After root-trimming, I repot the trees back into the same tub using fresh mix.  Also, the 18-gallon tubs provide a good ratio of growing mix volume, to tree roots.  Roots can fill a 5-gallon bucket in just one season, and then, plants can be stressed.  It will take at least 3-4 years for the trees in tubs to become root-bound, and by that time, it's time to root-prune, anyway....  I wait for the tubs to dry out before lifting/moving.  So far, no hernias.


Frank

EDIT:
Containerized fig trees will require far more attention in respect to proper watering, and fertilizing schedules than trees planted in the ground.

I top out at 15 gallons currently but would go larger if it wouldn't sacrifice storage space. I am trialling a 20 and a 25 gallon pot this year. I haven't found the "answer" yet but in 15 gallon pots my trees seem productive enough to warrant patience. 

I think for me a 7 gallon pot will be the final size, but only experience will tell..

I think the main thing to mention and think about here is a fig is a "TREE".  Which means it can get huge if you let it.  Like most have said, the largest container is your best option.  But some folks think that 5 and 10 gallons is large enough.  Well, no way!  The largest is best....period.  And yes, you're going to have to find a way to tote that large container around.  I have my largest trees in half whiskey barrels and have food grade 55gal barrels cut in half.  And guess what?  Those dudes are heavy!  I put caster wheels on my whiskey barrels.  But I also have my SON.  HA HA! 

But mostly I use a commercial dolly with a long tongue and a strap.  I slide the dolly under the tree and strap the rope around the container, tilt and go.

Go with the largest container you can find.  Make sure it is thick too!  A tree growing in the hot sun is no joke.  If you try to move it and if the container is that thin black plastic, guess what will happen?  The container will split.  Been then....done that!

I am just starting out, trying to figure out what I will do with my new figs as they get larger.  For the figs I hope to keep in containers, the 5 gallon size seems enticing due to the lower weight and the availability at a low price.  Ten gallon buckets are not as easily obtained.  More than that will be harder for me due to their weight and storage area limitations (not to mention being 58 y old).

Questions are:
how large would you expect a fig tree to get in a 5 gal bucket (SIP)?
how large in a 10 gal bucket/pot (SIP)?

Figs may get big, but only if you let them. They can be grown very successfully in small containers. I've grown almost any fruit you can name in 5-10 gallon containers and they've all fruited. It's mostly the people who haven't tried small containers who think they won't work. Properly grown you'll get more fruit from five 5 gallon containers than from one 25 gallon container. And they'll be much easier to handle.

Not that big containers won't work, they certainly will. I've had some great trees in 30 gal containers. But more commonly in that size I've gone 4 trees, figs, berries, or vines, all work and fruit.

What's not to like about this kind of production in a 3 gal pot?

Sorry about the big picture, I'm still learning.

Finding those hand trucks with long lifting tines is my problem.  We only have short ones that I've found so far.  I'll keep looking.  :)  So far I've topped out @ 25 Gal but I have a few 40 gal I haven't used yet except to mix soil.  I got lucky and found a nursery that had almost an acre of used pots.  I rented a U Haul to get the biggest ones out of there.  My evaluation size is 7-10 gal because there were over 100 of them.  :)

To keep the pots as light as possible I use pine bark, Floor Dry and peat.  I add small amouts of worm castings and Espoma bulb tone.

I'm wondering if those who need large containers aren't growing their figs at excessively high vigor. High enough that the plants get too big for small containers before fruiting. If so slow the plants down to an internode length below 3 inches. I think they'll fruit on small plants if grown more slowly.

This is great feed back, Thanks everyone. One other related question is that heavy pruning to keep the tree within the container limits does sacrifice breba crop. Problem? Also I've let the roots grow out from under the bucket and into the ground. That has helped a lot.

Hand trucks even with the small platform can move a 55 gallon barrel full easily, just add a ratchet strap or two and the hardest part is getting it to tip backwards so you can move it, I have been moving my 35 gallon pots with this and works quiet well.  You may want to get different tires as the pneumatic ones on mine are having a tough time supporting the weight, you can get never flats which are just solid rubber.

personally, i think in ground is the best option if you have the land and climate is optimal for the trees. however, if that is not possible, or if you like to move the tree around, container will have to do. i do wish i can utilize 20 gal or bigger containers. but that will take a lot of room. with 2 car garage for the winter, and the space being used for my wife's car, i get even less space. over the weekend, i did inventory of my trees. including the trees that i do not remember what they are, i have 20 trees that are producing figs, and 52 that are in the 1 gal. including 11 varieties that i'm rooting right now.. i have no clue how many trees i'll have by the start of the spring. 5 of those are old enough and in 10 gal. 15 of them are in 3 gal, but number of them will go into 10 gal sometime soon since they have shown that they are worth keeping. i know number of 1 gal will go into 3 gal and few into 10 gal also. that limits my space even further., 

what is good for the tree won't always work out for the person growing the trees. all we can do is best we can to let the tree grow and harvest modest amount of figs to enjoy them for awhile. 

Greenfig, I do agree with you. Here those guys are called Marseillais . When they tell you they have seen a big bull, expect to see a small rat ... But who knows, big bulls do exist as well.
----------
As for the containers - The best I've seen are the wooden ones. They have an Iron frame + Iron bottom - with wood to make the sides.
The sides are screwed to the frame, so that when you want to root prune/check the roots, you just unscrew one side at a time. Of course they are not cheap, and usually they are used by botanic gardens (for orange trees).
Did I mention they are on wheels with a small brake system ... So really handy.

As for size 80L=20 gallons, to my experience, is the most a human back can reasonably carry - The best is being 2 persons to carry it . So if you're looking for something manageable, you should try at 10 or 15 gallons ( 40 to 60 Liters).
I carried a 80 L potting mix bag on my shoulders - and that was already a nice promenade.

To help with the weight :
There are heavy duties hand trucks with 3 wheels on each side, if I had those shuffle constraints I would definitely buy one to move the pots around - and I would ask to someone to help for that task.
There are as well small hand cranes that can help you lift the pot up while loading them on the hand truck.
The main goal for using those tools being not to brake the pots when moving them around - I don't move my 80 L pots as they are buried in the ground.

The two problems for me are, the smaller the pot the harder it is to keep it watered properly, and the thinner the stems are - I saw that on a brownturkey that came in a 5 Liters pot. Once in the ground, the stems really thickened  ( width * 5 ).
The first stem was from the pot, and the two new came back from the ground - after winter complete die back . But to be precise, it did fruit in the 5L pot from the nursery - it came with one fig .
At nurseries, I often see figtrees in 5L pots being sold with 2 or 5 figs on them .