Figuring out the right size liner bag for your specific urban trash bin is simpler than you might think. The most reliable method is to grab a tape measure. First, measure the height of your bin from the inside bottom to just below the rim. Next, measure the circumference (the distance around) the top opening of the bin. For rectangular bins, measure the length and width of the top opening instead. Jot these numbers down.
Now, check the packaging of any box of liner bags. Manufacturers always list the bag's dimensions—typically the width and the length (which becomes the height when the bag is in the bin). Your bag's width should be slightly *larger* than the circumference (or length+width for rectangular bins) of your bin to ensure a good over-the-rim fit. The bag's length should be *greater* than your bin's height, allowing for a generous cuff over the edge for secure tying.
A good tip is to look for a bag that is about 1.5 to 2 times the height of your bin. This extra material lets you fold the top over the rim, which helps hide the bag and keeps it securely in place. If your bin has a unique shape or a swing lid, you may need to consider a slightly taller or more flexible bag. Remember, a bag that's too small will slip inside and be useless, while one that's excessively large is wasteful and harder to manage. Taking two minutes to measure saves you from messy spills and frustration later.