The short answer is that our standard round trash can does not have one universal inside diameter. For the common industrial 55-gallon round trash can, the inside diameter is usually about 22.5 inches (572 mm). For our standard household and commercial round models, the inside diameter commonly ranges from about 7.9 inches (200 mm) for small 5 L bins to about 19.7 inches (500 mm) for large 120 L bins. Typical examples include a 10 L round bin with an ID near 9.8 inches (250 mm), a 20 L bin near 11.0 inches (280 mm), a 30 L bin near 12.6 inches (320 mm), a 50 L bin near 14.6 inches (370 mm), and an 80 L bin near 17.7 inches (450 mm). These figures are not fixed rules because the inside diameter changes with capacity, height, wall thickness, taper, material, and lid design. We measure the inside diameter across the top opening from inner wall to inner wall, excluding the rim and reinforcement. If the bin is tapered, the bottom inside diameter will be smaller than the top inside diameter. Our normal production tolerance for round trash cans is usually ±1% or ±2 mm, whichever is greater. For custom orders, we can manufacture to an exact ID, such as 250 mm, 300 mm, 350 mm, 400 mm, 450 mm, 500 mm, or 572 mm, depending on the mold and material. To confirm the correct size for your project, please tell us the capacity, overall height, material, lid type, and whether the bins need to nest or stack. With those details, our trash can factory can provide the exact inside diameter, top and bottom dimensions, and lid fit. If you need a widely recognized standard, the 55-gallon drum-style round can at 22.5 inches (572 mm) ID is often the closest match, but for kitchen, office, medical, or street bins, the inside diameter will vary by model. Send us your target size and we will match it or build a custom mold for you.