The “kind of accepted” standards are these: 

  • a 4" pot= a pint 
  • a 5/6" pot= a quart 
  • an 7/8" pot= a gallon 
  • (there are also 2 gallon sizes, though harder to find) 
  • a 10" pot = a 3 gallon 
  • a 14" pot= a 7 gallon 
  • a 20" pot= a 10 gallon 
  • a 24" pot = a 15 gal 
  • a 30" pot= a 20 gal 
  • a 35" pot = a 25/30 gal

Pot sizes for trees and plants.

Container garden design.