That's a great and often overlooked question! Picking the right size trash can is more art than science, but a few practical checks can save you from a bulky eyesore or a constantly overflowing bin.
First, think about physical space and flow. Stand in the spot you have in mind. Is there a clear 3-4 foot (about 1 meter) walking path around where the can would go? If placing it would force people to squeeze past or step into a street, it's likely too big. Also, check for "visual clutter." Does it block sightlines for drivers, cyclists, or shop windows? A can that dominates the view is probably oversized for that niche.
Next, consider realistic capacity needs. A giant bin in a low-traffic alley will look neglected and attract pests because it fills too slowly. Conversely, a tiny bin outside a busy cafe will overflow daily. Observe the area for a day or two. How much litter is actually generated? A good rule is to choose a size that needs emptying 2-3 times a week under normal use—this balances cost and cleanliness.
Don't forget practical access. Can maintenance crews easily get their truck or cart to it for emptying? If they have to maneuver a huge, heavy bin through tight spaces, you've created a workflow headache. Also, peek at local regulations. Many cities have guidelines on street furniture dimensions, setbacks from curbs, and even approved models. Your public works department is a great resource here.
Finally, trust the "look and feel" test. A well-sized bin feels like a natural, helpful part of the streetscape, not the main attraction. If you look at it and your first thought is "That bin is huge!" rather than "That's a convenient place to toss my coffee cup," then it's a sign to consider a smaller, more proportionate option. It's all about blending function with the environment.