That's a great question that gets to a practical detail many people overlook. The short answer is: a square or rectangular trash can typically has a greater usable capacity than a round one of the same listed gallon size.
Here’s the natural breakdown of why:
Think about fitting bags and trash inside. A square can has corners that bags can fill out. A round can naturally creates empty, unusable space in the curved walls when you put in a standard rectangular bag—the bag bunches and doesn't utilize the full diameter. So, for the same nominal volume (like 32 gallons), the square design often gives you more *usable* space.
It's also about space efficiency. Square cans fit flush against walls, fences, or in corners, maximizing the area they occupy. A round can with the same footprint (the base area it covers) will always have less internal volume because of the curved walls. A square can use nearly all of its footprint for storage.
However, capacity isn't the only factor. Round cans are often more stable in windy conditions as wind flows around them. They also don't have corners where debris can get trapped. Square cans, while often holding more, can be harder to clean in those corners.
So, if your primary goal is maximizing capacity for the space you have, a square or rectangular model is usually the winner. But consider where it will go and how you'll use it—sometimes the practical advantages of a round can outweigh the pure capacity benefit.