i didn't know, only what the manufacturer said. he said 19 gals but first fill was only 15.5 gals.. the overall length is 34" the width is 13" and depth is 10" which would equal, 19.134199 gals. but the filler neck is 1 3/4 and is a side fill it would seem you would have to deduct the diameter of that, which equals 15.785714 gals., about what i was able to fill it with. i was hoping i had about 4 to 5 gals. reserve on empty. thanks for the responses. RON
