Enter your trash can's dimensions — width, depth, and height — along with its shape (rectangular or cylindrical) and preferred overhang, and the Garbage Bag Size Calculator tells you exactly what bag width and bag height you need. No more guessing at the store or ending up with a bag that slips into the can or barely reaches the rim.
Recommended Bag Height
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Recommended Bag Width
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Approximate Bag Volume
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Dimensions Unit
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For a rectangular bin, the bag width equals the bin's length plus its width (Gw = Tl + Tw). The bag height equals the bin's height plus the overhang plus one quarter of the bag width (Gh = Th + Go + Gw/4). For a round bin, the bag width equals the diameter times π divided by 2. These formulas ensure the bag covers the bin floor, reaches the rim, and hangs over the edge securely.
Using the rectangular formula: bag width = 8 + 12 = 20 inches. Bag height = 22 + 4 (overhang) + 20/4 = 31 inches. So you'd look for a bag approximately 20" W × 31" H. A standard 13-gallon kitchen bag (24" × 27") may work for smaller bins, but a 33-gallon bag would be a closer match for this size.
Heavy-duty industrial or contractor bags can reach 60" × 68" and hold up to 95 gallons. These are designed for large drums, construction debris, or yard waste. For home use, the largest commonly stocked size is typically 55 gallons (36" × 58").
Standard retail sizes include 4-gallon (small bathroom bins), 8-gallon, 13-gallon (kitchen), 20-gallon, 30-gallon, 33-gallon, 39-gallon, and 55-gallon (large outdoor or commercial bins). Industrial sizes extend to 65 and 95 gallons. Matching the gallon capacity of the bag to your bin's volume helps ensure a proper fit.
An overhang of 3 to 6 inches (7 to 15 cm) is generally recommended. Smaller bins like desk or bathroom cans do well with 3 inches of overhang, while large kitchen or outdoor bins benefit from 5–6 inches to stay securely in place and resist being pulled into the can when filled.
Yes. Rectangular and square bins use a length-plus-width formula for bag width, while cylindrical bins require the diameter multiplied by π/2. Using the wrong shape formula can result in a bag that's too tight at the base or too loose at the rim. This calculator handles both shapes automatically.
Yes — going one size up is generally fine and gives you extra room to tie the bag off. However, an excessively oversized bag will bunch up at the bottom, which can trap liquids and create odors. Aim for a bag no more than 10–15% larger than the calculated dimensions.
Multiply the bag width (in inches) by itself, then by the bag height, and divide by 231 to get a rough gallon estimate for a rectangular bag. For cylindrical estimates, use the formula V = π × r² × h / 231. Keep in mind that bag manufacturers measure capacity based on filled volume, so the listed gallon rating may differ slightly from purely geometric calculations.