Trash Bag Size Calculator

Trash bag sizing matches bag dimensions to bin volume, ensuring the bag fits properly with enough overhang to fold over the rim without slipping in or bunching at the bottom.

Bin volume formula (rectangular bins): Volume (cubic inches) = Height × Width × Depth (all in inches) Volume (gallons) = Cubic Inches ÷ 231

For cylindrical bins: Volume (gallons) = π × radius² × height ÷ 231

Bag sizing rules:

• Bag height should be approximately equal to the bin height plus 4–6 inches for the fold-over lip
• Bag circumference should be ≥ bin circumference (measure around the widest point of the opening)
• 1 gallon = 231 cubic inches = 3.785 liters

Bag packaging almost never prints circumference. It prints a flat width, because that is how the bag lies in the box. A bag lying flat is half its circumference, so the number you want on the box is half the distance around your bin’s rim. Measure the opening rather than the base: most bins taper, and a bag sized to the narrow bottom slides down inside the moment there is any weight in it.

Standard bin sizes and recommended bags:

Bag thickness (mil) guide:

• 0.7–0.9 mil: Light duty (office paper, bathroom waste)
• 1.0–1.2 mil: Standard duty (household kitchen waste)
• 1.5–2.0 mil: Heavy duty (wet waste, sharp objects)
• 3.0+ mil: Contractor bags (construction debris, yard waste)

Worked example: A kitchen bin measures 12 in × 12 in × 24 in tall. Volume = 12 × 12 × 24 ÷ 231 = 3,456 ÷ 231 = 14.96 gallons Best fit: 13–16 gallon bags with drawstring closures. The rim measures 2 × (12 + 12) = 48 inches around, so look for a flat width of at least 24 inches and a bag height of at least 29 inches.

Round bins: A cylindrical office bin 10 inches across and 15 inches tall holds π × 5² × 15 ÷ 231 = 1,178 ÷ 231 = 5.1 gallons, so a 7–8 gallon bag. Its rim is π × 10 = 31.4 inches around, giving a flat width of about 16 inches. Round bins are where the flat-width check earns its keep, because a bag cut for a square bin bunches badly in a cylinder.