A BOX THAT'S 18X18X24? IS IT A BIG BOX?WHAT IS SOMETHING I CAN COMPARE IT TO, TO SEE HOW BIG IT IS?

I'M TRYING TO MOVE TO ANOTHER STATE AND SOMEONE SUGGESTED INSTEAD OF PACKING A MILLION BOXES GET (6) 18X18X24 BOXES? I DON;T HAVE A LOT JUST CLOTHES,SHOES, BOOKS ETC. USPS BOXES ARE TOO SMALL AND THERE'S A MILLION OF THEM IN ORDER TO PACK EVERYTHING!!AND I WILL BE SHIPPING THESE USPS!I'M IN MN SENDING THEM TO HOUSTON TX