What Size Are 45 Gallon Trash Bags? | Dimensions That Fit

A 45-gallon trash bag is typically 40 inches wide by 46 or 48 inches high, sized to fit a standard 45-gallon trash can.

The answer to what size 45 gallon trash bags come in depends on the can you’re lining, not the bag’s volume. The “45-gallon” label refers to the container it’s made for. Most US retailers, including Grainger and Staples, stock 45-gallon liners in two dominant dimensions: 40″ x 46″ and 40″ x 48″. Some manufacturers also offer 39″ x 46″, 40″ x 50″, or 43″ x 48″ versions to suit different can shapes and closure styles.

Retail listings confirm the two most common sizes. Grainger’s 45-gallon trash bag measures 40 inches wide by 46 inches high with a 60-pound load rating.

The extra two inches of height gives more overhang for taller cans or flap-tie closure. You’ll see both sizes on store shelves, and either can correctly be called a “45-gallon trash bag.”

How To Measure Your Can For The Right Bag Size

If your can doesn’t match standard dimensions, use quick measuring math. For a round can, multiply the diameter by 3.14 (pi), then divide by 2 to get your bag width. For a square or rectangular can, measure the perimeter, divide by 2, and that’s your width.

For height, measure the can and add 4 to 6 inches for overhang over the rim. Some guidance recommends adding a bit more —

Why The Same Gallon Rating Comes In Different Sizes

Don’t buy by the gallon label alone. Can shape, wheeled bases, and closure types all change what fits. A round 45-gallon can might take a 40″ x 48″ bag best, while a square commercial bin often fits the 40″ x 46″ version snugly. Drawstring bags and flap-tie styles add material at the top that alters usable height.

Thickness matters too. Available 45-gallon bags range from thin 0.39-mil liners to contractor-grade 2.0-mil or 2.3-mil options. Check the mil rating for sharp, wet, or dense trash.

When you’re ready to stock up, our tested roundup of the best 45 gallon trash bags on the market compares the top performers by thickness and value.

Common Sizing Mistakes To Avoid

• Mixing up capacity and dimensions: The “45 gallons” is the can capacity, not a measurement of the bag’s volume. A bag labeled 45 gallons simply fits a 45-gallon container.
• Skipping the width check: A 40″ x 46″ and a 40″ x 48″ bag both say 45 gallons, but they fit differently on tall cans.
• Ignoring can shape: Round cans need the pi-based calculation; rectangular bins need the perimeter method. Using the wrong one leaves you with a bag that’s too tight or baggy.
• Assuming uniform strength: A 0.39-mil kitchen liner won’t handle construction debris that a 2.0-mil contractor bag carries easily.

Should You Size Up Or Down?

If your can measures between standard sizes, size up rather than down. A slightly larger bag gives you more overhang for tying and prevents the liner from slipping into the can mid-week. Just confirm the width fits your can’s opening — a bag too wide for a narrow can bunches up and tears at the rim.