CO2 cylinder size?

I'm slowly getting into kegging buying pieces here and there. What size cylinder should I be looking for? I know 4-5lb may be the minimum, but is that too small? Is a 20lb too large?

Any advice, trial and errors, and experiences welcome.

Thank you

I use a 5lbs. in my fridge. Suits me well. I have a twenty pounder that I used to do transfers, seal lids, etc.

Most of the cost of a refill/swap is the labor, so filling a 10# tank is only a couple $ more than a 5#, and a 20# is only a couple $ more than a 10#. For this reason I chose to get the biggest tank I could comfortably fit. A second tank for when you run out of gas right before a party on a Sun when the welding shop is closed can be really handy too.

20lb is the way to go. The cost to exchange a 5lb and a 20lb is about the same so its really a no brainer. Having both is ideal, the size of the five makes it perfect for taking camping.

Definitely get the biggest one that will fit your application. I have a 5lb cylinder, because that's all that will fit in my kegerator, and I can carb and serve about 6-8 kegs off that tank.

I'm working on restoring a 1949 Crosley Fridge, and have my eye on a 12lb tank that will fit in there. I thought about getting a 20lb tank and keeping it outside the fridge, but cold CO2 performs more consistently than room temp CO2, so I'm just going to get the biggest one that will fit inside the kegorator.

Thanks for the responses. Is it a better idea to buy one from like a craigslist, welding or online source? I have no idea. I'm assuming that they are like propane tanks and have dates on them. Is it easier to buy one from somewhere that will swap them out?