Potting mix is sold in cubic feet. Smart Pot provides the amounts needed to fill each of their containers on their website - linked the page below. Check out all their other FAQs too.

Depending on the mix and how much it compacts when wet you will need a little more than they call for so get extra.

But keep in mind that it is the quality of the mix that you put in them that is crucial.

Dave

Here is a link that might be useful: SP - How much mix do i need.

Thanks, they are actually called Phat Sacks from HTG Supply. I said smart pots because I couldn't remember the name, I know there are quite a few of them. I am using Miracle Grow but with the moisture control because that is all that is available locally. I have used it in a couple of pots with tomatoes in the past with good success, but why would it be a problem? I find keeping them watered in summer heat to be easier with the moisture control. They are not self watering containers. Many potting mixes are in cubic feet but for some reason the bag from costco is in quarts. I swear they do this stuff to make it hard compare prices. I have 3- 20 gallon and 2- 7 gallon pots so I figured 6 bags. I have 5 1/2, and I will probably pick up 2 more so I have extra for potting a few other flower containers.

Miracle Grow but with the moisture control

If it works for you, fine. Many have reported here (and on another forum we can't name) that it keeps the plants too wet when used in smaller containers or SWC leading to root rot. I know Raybo had issues with it even in his big Earthtainers and I respect his knowledge and experience working with it. But they are SWC too.

I have only used it once since reading all those comments but at the time it was an emergency quick fix and I mixed it with lots of ProMix I had left over. Had no problems but can't say how it would work straight or in a non-SWC.

I am surprised that it is the only thing available however. Is this from Costco and is MG and labeled in quarts only? Weird!!! They must be the small bags.

Scott's says it comes in "8qt., 16qt., 1 cu. ft. , 32qt., 1.5 cu. ft., 2 cu. ft., 55qt. and 64qt." See US Dry quarts to cubic feet conversion chart

Is it the Potting Mix or the Garden Soil? They both come in Moisture Control formats. Do NOT use the Garden Soil in any container.

Dave

The attached photo, taken back in early April, shows some of my 20 gallon Grow Pots. Each one perfectly held one 64 qt. bag of StaGreen potting mix, which I found to be an excellent mix, not lots of big wood chips etc. Now they are full of peppers and tomatoes, all doing very well in the fabric containers. Good luck with your maters!

Here's what some looked like a couple of days ago!

I should have added that I did mix in 3-4 big double handfuls of peat moss into each container! The 64 qt. bags are approx. 2.49 cf.

Not sure why it is weird, but it is the 55 qt size that you said Scotts lists as one size it comes in. So, again, not sure why its weird. I could probably get something else at Agway since they will special order sometimes but the price would be quite a bit higher. Walmart only carries the mix with the moisture control and so does Costco. HD might in smaller bags only, but I am not sure. Last year they only had the moisture control in large bags. Mostly I would have to mix my own and mixing large amts of soil does not appeal at all. I went store to store a couple of years ago looking for the non-moisture control for transplanting seedlings at the advise of people here and gave up. I never found it. Only garden soil and potting soil that are way too heavy, not in the potting mix. Most of my plants go into the garden, I only have about 2-3 in pots last year and will probably have 3 this year. Just for that it is going to cost me about 60.00 in potting mix, and thats a lot for tomatoes, lol. (Well, a couple of pepper plants in there, too.)

Sorry, I just meant that it is weird to hear about such a limited selection of brands and types available in what I'd consider a heavily populated and commercial area.

Our nearest town (pop 8,000) is 25 miles away yet there are easily 20 different sources for 8-10 different brands of potting mix in that town.

I guess there just isn't the demand for it there or CT folks aren't supposed container garden, huh? But I do envy you a Costco. Folks on the Harvest forum talk about the bulk food bargains available there often. Nothing like that within 100 miles of here.

Dave

I think you hit it on the head, Dave. It is a heavily suburban area and I see little container gardening except for annual flowers on steps. Almost everyone who wants one has a garden, even if its small. Only apartment and condo residents need containers and they usually make do with one or two pots with a veggie plant in it. Trust me, I give away about 75 plants per year and most people with apartments have no idea what to do with them. When I tell them they need a really BIG pot they think 10-12 inces in diameter, lol. :) They are agast when I tell them that little tomato can grow to over 6 feet tall.

Just like when I was looking for pickling salt - looked in the big chain stores, Walmart, a small mom & pop grocery 7 miles away. Finally found some on the bottom shelf of a family-owned grocery "chain" (2 locations LOL) that's been in business 90 years, 11 miles miles away in the other direction. Lots of pectin (and Gulf wax) but people in CT apparently don't can anything but jam (or grow anything but flowers) LOL.

I have noticed over the past 5 years or so, local retail businesses, even the large chains, have scaled way back in the brand variety they offer. This is a pervasive change extending from home and gardening items to groceries and it is not a happy one for the consumer. I am ordering more and more online. But so far I have not starting getting soil online. Most places now only stock one "name brand" and maybe a store brand. They used to carry mulitple formulaitons of Miracle Grow, Hyponex, Pro and generic versions. Now Miracle Gro with moisture control and sometimes a generic is all I have found.

The easiest way to calculate your soil needs is with basic math. For those of us who hate math, use an online calculator.

https://www.soilcalculator.com

Is is a good one because it shows you exactly how many bags you will need and allows you to add different potting containers of different sizes all at once.