I bet someone might have asked or explained this before but I got googled out and can't handle more searching. So here's my question.

Is there any way to decipher the 'codes' on the bottom of plastic garden pots to know the size of a pot? I realize that one needs a magnifying glass but that's not enough. It's easy to read the recycling number but I'll be danged if I can tell if there are numbers indicating size, such as a 4 for a 4" pot or 6 for a 6" pot, etc.
And to add to my confusion, sometimes I might see that a pot is a 'geranium' pot (without the size) or that a pot holds 1.25 qts or or or. Even have some with no markings.
Can anyone help? Please?

@tx_flower_child

Problem is, there is no universal standard. Each vendor is a bit different. Five vendor's "gallon" pot may be slightly different structure as well. Even ordering a plant can be confusing as some use the term gallon when in fact it is a "trade gallon" which is actually ~ 3 quarts.

The term "geranium" pot is a style. There are many others - e.g Azalea pot.

Not sure where you are going with this, but I just organize all my pots by size and stack as best I can. After a lot or practice/experience it is easy to judge what size one needs.

If you are ordering, typically they will give you height and opening width, sometimes width at bottom.

Many times there is little indication other than 2" or 3 " pot. A 2 " pot is going to be a tiny plant.

Again, once you get above gallon size, pot structure can be all over the map. Buy 5 different 5 gallon plants and chances are every pot will be different size/structure. This is especially true with the bug name - e.g. Proven Winners.

Hope this helps some.

I guess you can use a ruler but there is immense variation out there. Sometimes you can get good info by googling the alphanumeric code they stamp on the bottom. The width of the useful portion can be much less depending on the size of the lip.

Plant vendors typically overstate the sizes of the pots (by for example using the diagonal measurement of a square pot), but of course each case is different.

As David pointed out, any pot size in gallons also overstates the volume by about 50% unless it is given as "true gallons" (almost never the case).

It can be a useful exercise to.calculate the volume of a given pot based on your measurements of its width and height. For example the pots I use to grow succulents (mostly wider than they are deep) approximately double in volume with each small increment from 4"-5"-6"-1gal-8"-10". When you do the math there is a compelling argument for using the smallest applicable size to save money on soil (volume) and shelf space (area).

I will add to that by saying when a vendor says 4" pot, it may be a tall or regular 4" pot, which of course changes the volume. The same applies to larger pots...so be aware when buying on line. A regular would probably be fine for cacti or succulents, but not for most herbs or perennials, that have deeper roots. I used to carry a small 2"x2" tape measure in my purse when shopping. It came in handy.

Baja_Costero said: [snip good stuff] When you do the math there is a compelling argument for using the smallest applicable size to save money on soil (volume) and shelf space (area).

When actually using a pot, I do that for sure. Start with the smallest that works. You can always pot up. In addition, many plants will do much better with roots a bit cramped rather than a huge oversized pot where the plants spends too much energy filling the pot with roots rather than growing the plant.

[And yes I know - in a way that makes no sense when you think about pla plant in the ground where it is not constrained.]

Getting off topi, but I hope this is helpful to the OP.

Certainly a surprisingly helpful and interesting conversation, for a seemingly simple question.

I agree: plant pot sizes and shapes are all over the map.

Here are some sizes and volumes for METRIC pots used by Jackson's Nurseries. They give top diameter, bottom diameter, and height. But even so, they caution:
>> "Sizes are only a guide as the exact measurements vary depending on pot manufactures."

http://blog.jacksonsnurseries....

This site offers a rough estimate of how many gallons will typically be in a pot called "so many inches", though they complain about how non-standardized pots are. They say they wnat to offer some standard for pot size/volume, but then they don't say whether their inch measurement refers to height or diameter!

http://www.hardytropicals.org/...

This site is similar:

http://www.harvesttotable.com/...

I think the only way to know to know how many gallons or cups a pot holds is to block the holes with a plastic bag and then fill it with water from a measuring cup or quart or gallon jug. (Not very helpful for planning purposes when buying pots online.)

Or do the math: Volume = pi X Radius^2 X Height

Or: Volume in cubic inches or cubic cm =
. . . . . . . . . . Usable height X (average diameter squared) X 0.785

(.785 is pi/4)

14.4 cubic inches per cup
237 cc per cup

231 cubic inches per gallon
3785 cc per gallon

I buy pots from the East Jordan Plastics company. If you download the PDF catalog you can see the information for each of their pots including diameter and height measurement in inches, cubic inches, US and Metric Liquid volume.
http://www.eastjordanplastics....

RickCorey said:I think the only way to know to know how many gallons or cups a pot holds is to block the holes with a plastic bag and then fill it with water from a measuring cup or quart or gallon jug.

It's probably easier (for smaller sizes) to fill a pot with soil and then dump it into a measuring cup. Just be sure it's reasonably well packed both times.

Also consider dumping soil from one container into the next size up if you want a direct idea of how much bigger it is, using the eyeball method to judge relative quantity instead of breaking out the measuring cup or doing any math.

Well, thank you everyone for your input. Y'all have confirmed what I suspected. There are no real ANSI standards for garden pot sizes.
This basically started as a matter of trying to read the numbers on the bottoms of pots - - - by that I mean if the pot is flipped over.

At one time or another I have had literally hundreds of pots stacked here and there in my yard and my garage. Neighbors give me their empties. A clerk at one of the nurseries I frequent said she had some empties. Her definition of 'some' ended up being 2 trunk loads. (She drove a Cadillac.) Someone the next block over from me set out 80, yes eighty, large (10 gallon on up) pots for bulk trash to dump in the landfill.

Why collect them? When I was active in DG we had 'Round Ups' where we would meet, greet, and eat and also swap plants. New to gardening, I didn't have any plants to swap. So I would bring pots. (Please note the 's'.) What people couldn't use I'd take home, keep some, donate some to other organizations, and then take 'leftovers' to a nursery that recycles.

So now, for the ones that I have kept, I was attempting to determine sizes for transplanting mostly indoor or indoor/outdoor plants. Yes, I know what a 4" pot looks like. But if I need to pot a plant up to a 6" or 8" then I was hoping that the flip side of the pot would give me a clue as to its size. That's when I started out with a magnifying glass and google and ultimately went crazy. No, make that 'crazier'.

As sallyg said, 'Certainly a surprisingly helpful and interesting conversation, for a seemingly simple question.'
Indeed.
Thank you all and let me know if you need any pots. (Again, note the 's'.)

tx,
I'm fairly confident that no one here finds anything strange about your collecting multiple pots. Even many multiples.
I keep a good number of extras, for swapping, and also just so I should always have the exact size, and depth, pot I want for any plant. Multiples are stacked in a milk crate, odds are stacked as well as they can be. I bet I have easily a hundred+ empty pots. Way more than I need. Way less than a lot of people.

Cadillac trunk fulls! That's A LOT

tx_flower_child said: ... Neighbors give me their empties. ...

Good neighbors! It also suggests that you must be a good neighbor - do you share veggies, flowers, or plants with them?

Someone suggested a way to store pots that keeps them from blowing around: pound a length of rebar into the ground deeply enough that it won't tip over in a high wind. Then stack pots open-side-down with the rebar sticking up through their center bottom hole.

(When I give things away, I try to give away my odd sizes first, so that what I have left is more uniform.)

I have easily 1,000 + pots behind my greenhouse. My way of recycling was to use up my old pots when I was actively growing and selling at the local Farmer's market.

I donate a lot to my Master Gardener group and we go thru hundreds at out annual plant sale.

@sallyg - yes, Cadillac trunkfuls! But that's not the whole story. It started when I was at a neighborhood nursery and spotted some of those plant flats in the trash. So I asked the clerk if I could have them. I told her about the group 'Round Ups' and that there would be people who could use them. And I said that it was almost time for the next get together. That's when she told me that she had a lot of empty pots if I wanted them. She told me when she'd have them with her and to park near her car. The day comes and whoa! Not only was it a trunkful, but those danged pots weren't stacked or bagged but just loose. That Caddy was filled to the gills. Well I couldn't turn them down but I really was in a mild state of shock, especially when she said to come back the next day and she'd have more. So I did and she did.
Some months go by and I happen to be at the nursery on one of the days that she works. She asked me if I'd like more pots. She offered to fill up that dang old Caddy again. This time I just smiled and politely told her 'another time'.
Sure makes me wonder what she'd been up to. She's semi-retired and I bet she has that part time gig clerking at the garden center to support her habit.

@DavidLMO - I'm by no means a Master Gardener, but most of the donated pots go to people who are and they also use them for plant sales. And that's a good thing.

@RickCorey - I once posted a note in a thing called Nextdoor Neighborhood. (A lot of cities have that now or so I hear.) I let people know that I'd be glad to take their empty pots. At first people would leave a few by their garage or alley and I'd go pick them up. After awhile I didn't have to go get them from people. I'd just walk outside and there would be a little stack of empty pots. Thankfully never enough to fill up a car trunk.

Wish I did grow vegetables. I'm surrounded by trees and I'm lucky to have enough sun to get some perennials to grow. Just a small house on a small lot in a big city. But when I lived in Austin, the house was on 2 lots so we had big vegetable beds and several large herb beds. Had plenty to give away. Kept a cousin and her 2 daughters supplied with lots of lettuces, spinach, herbs, peppers, etc. We'd meet once a week at a nearby watering hole and drink 'ritas until the girls school let out. Then we'd go to the house and bag up whatever they wanted. It was fun. Also gave away a lot of plants to the kids who went to U of Tx. We were on a route that the kids who walked or biked to campus would take. Anyway, that was then and this is now.

So I do have a lot (for me) of native perennials and I've been gathering seeds. Please send me a tree-mail if you want free seeds. Got lots of various milkweed seeds. Take them. Please.

Oh, that reminds me, the neighbor behind chatted with me, admired what they could see of the gardens, and asked if I wanted his spare pots. So every once in a while, I'd go back to the corner and find presents tossed over the fence
I also got lots of them after Easter when another neighbor helped his church dispose of potted gift flowers. Pots plus decorative foil.

@sallyg - 'Pots plus decorative foil', eh? Dang!

I kinda wish the neighbors would shower me with gift pots! The way it is, I give away so many plants (this year maybe 250-300) that I find myself buying pots on eBay a hundred at a time from a guy who breaks down pallets and resells them. It's nice to be able to choose the kind I like (Poppelmann teku pots) which are the right shape and have the advantage of 15-20 holes at the bottom, ensuring excellent drainage for my succulents. I do recommend these pots as they are light and cheap and long lived (info available on the web).

I've tried offering a reward to people so they return with my pots, but it appears they like them as much as the plants.