you sure you're not confusing it with 15 gallons like @davs said?
I measured my plastic garbage can with lid I have now. I want the same exact size .
I buy the 150 pack of 13 gallon Glad white garbage bags. Im looking at it as I type.
Works fine for me. Been using it this way for 20 years. Besides you try to fill a 13 gallon glad white garbage bag and you got one big mess. They tear easy.