Figuring out the right size liner for your outdoor trash can is simpler than you might think. You don't need to guess or deal with bags that are too small and slip in, or too large and look sloppy. The most reliable method is to grab a tape measure.
First, measure the circumference (the distance around) the top of your trash can. If it's a rectangular can, measure the length and width of the opening and add them together, then multiply by two. For a circular can, measure the diameter (straight across the center) and multiply that number by 3.14 (pi).
Next, measure the height (or depth) of your can. Start from the bottom inside and measure up to just below the rim. Don't forget to consider if your can has an overhanging lid; you might want to add a few extra inches to the height so the liner can be tucked over the rim for a secure hold.
Once you have these two numbers – the circumference and the height – you can confidently shop for liners. Look for boxes that list these dimensions. For example, a bag labeled "55-gallon" can vary between brands, but the exact dimensions will never steer you wrong. A perfectly fitted liner will stay in place, contain all the mess, and make taking the trash out a clean and easy task.