When a gallon ain’t a gallon

Like everybody, I have a list of pet peeves. Mine includes daylight savings time, tipping, the inability of our newspaper carrier to deliver a dry paper, and the size of nursery containers.

If you’ve ever measured the volume of a “1 gallon” nursery pot, you know that it’s not 1 gallon (3.8 liters). Not even close. In fact, depending on the manufacturer of the container, it might be as little as ¾ gallon (2.85 liters). That’s ¼ less than—well, what? Certainly not less than labeled because nursery containers typically do have the actual volume printed on the bottom. It’s simply less than we expect, based on the tradition of calling a #1 container a “1 gallon container”.

I had been wondering for a long time where this discrepancy comes from. Just the other day I happened to come across this discussion on GardenWeb. Never mind that it’s from 2005, the information is still good. A poster calling himself “calistoga” contributed what I consider to be as good an explanation as any:

As I understand it, we got into this "gallon" reference when the nurseries boomed at the end of WW2. Our government had contracted with canners to pack millions of one gallon cans of foodstuffs to feed the armed services. At wars end there was a very large surplus of one gallon cans available cheap that were grabbed up by the nursery growers. Since they WERE one gallon cans that was what they called them. When the surplus was gone and new cans were ordered a tapered can that would stack was a lot more practical. The advent of plastic made a tapered can much easier (and cheaper) to produce. The name "gallon" persisted even when the container would no longer hold a gallon of anything. Some time ago the weights and measurement people started looking into "false size claims". Since then the industry has been trying to eliminate any reference to "gallons". Hopefully in the near future the industry will decide on names for sizes that can be standardized and make sense to us all.

This makes total sense to me. So many of our traditions go back to some war or other.

Further research revealed that a “#1 pot measures 6" wide by 7" deep and has a capacity of 183 cubic inches (6). Once the plant has been put into the pot, and some space has been left at the top for water, ten #1 pots can be filled with a cubic foot of soil. With 27 cubic feet of soil in 1 cubic yard, a nursery can pot up 270 #1 pots with a cubic yard of either soil or container mix. If #1's are placed pot-to-pot, in rows 12 pots wide, with 2.5 foot alleys between, approximately 2,700 #1's can be set out on 1,000 sq.ft. of ground”.

If this didn’t make your head spin, you’re made of a stronger fiber than me!

More practical, at least for this spatially challenged brain, is this list of nursery container sizes from Moonshine Designs Nursery:

  • A "gallon" pot is also known as a "#1 trade size". It does not actually hold a gallon of liquid or dry measure. Actual capacity is 0.78 to 0.98 gallon.

  • 1 gallon "true gallon": 1.0 gallon 7" x 6".

  • 2 gallon: 1.9 gallon 10" x 7 3/4". 

  • 3 Gallon: 2.9 gallon 11" x 9 1/2". 

  • 4 gallon: 3.9 gallon  12 x 11 1/4". 

  • 5 gallon: 4.7 gallon  13 3/4 x 10". 

  • 7 Gallon: 7.5 gallon  15" x 12 1/2". 

  • 10 gallon: 11.1 gallon  18-1/2" x 12". 

  • 15 Gallon: 14.7 gallon  18-1/2" x 17"

Looking at this list, it becomes clear that the “gallon” pot is really the only one that has issues. Maybe we should all be buying plants in 2-gallon sizes and up? Or maybe we should simply stick to tradition, call a ¾ gallon container a “one gallon”, and pretend that I never wrote this post?

Readers in other countries, how are nursery containers measured where you live?


  1. What about the "tall" and "squat" pots? I've never considered nursery pot sizes to be volumes, just relative labels. I know a 2 gal. pot is bigger than a 1 gal. and that's all that really matters.

    I actually see '4" nursery pot' specified a lot now -- aren't those the "quart" pots? (I've never actually measured a 4" pot to see that it's actually that size, but I assume it's not)

    Other countries use metric I believe. It doesn't mean a 750ml pot definitely has a 750ml volume though, but I expect it does.
    It's not work, it's gardening!

  2. You might as well add 2 X 4 lumber to your pet peeves! An actual 2 X 4 that is planed is 1 5/8 X 3 5/8.

  3. Huh, I always wondered about this gallon business. Thanks for digging for the info!

  4. If you have to fill one thousand one gallon pots, then you would need to now how many cubit inches is in each pot. cubit inches X 1000=? how many cubit yards or tons you will need to fil all the pots. Now multiply that by five days a week for a year. At least 250,000 pots. You can use it for just one wheelbarrow load also.


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