Count your cushions first: 8 standard 20x20x4-in seat cushions plus 2 throw pillows hold 17,336 cubic inches of volume, which is 75.05 gallons — and with 20% packing clearance you need about 90.1 gallons. That lands in the medium tier (51-100 gallons), so shop a 90-gallon-class box. Deep-seat cushions take roughly 2x the space of standard ones, so count those separately in the size mode above.

Multiply the interior dimensions and divide by 231: 48x24x24 = 27,648 cubic inches / 231 = 119.7 gallons, a 120-gallon-class box in the large tier (101-150 gallons). Use interior dimensions, not exterior — a box advertised as 120 gallons can have a slightly smaller true interior volume once wall thickness is subtracted.

No. A typical 90-gallon-class box has an interior of about 45.3x19.0x22.3 in (roughly 83.1 gallons of true interior volume), so its longest side is 45.3 in — far short of 78 in. A full-length chaise cushion needs a 150-gallon-plus box, or it must be folded or rolled. Use the fit checker above with your exact interior dimensions.

Stand it on edge. A 20x20x4-in seat cushion laid flat needs 20 in of width, but stood on edge it occupies 20x4x20 in — which fits a 45.3x19.0x22.3-in interior (20 <= 45.3, 4 <= 19.0, 20 <= 22.3). Store flat cushions vertically like files to make narrow boxes work.

Many deck boxes double as benches. A 90-gallon-class box about 49.2 in long seats 2 adults (one seat per 24 in of length), and with a 485-lb-rated lid the weight limit also allows 2 adults at 185 lb each. Resin lid ratings range from about 485 to 770 lb depending on the model — never exceed your box rating, and check it in the bench mode above.

Treat waterproof as marketing: no commercial deck box is submersible. Most resin boxes are roughly IPX4-equivalent (splash-proof from any direction) when they have a rubber gasket and at least 1 in of lid overhang. For cushions, add lid vents so trapped moisture does not cause mildew. Use the weatherproof planner above for your exposure level.

For a 45x19x22-in interior built from cedar 1x6 boards: the exterior comes out 46.5x20.5 in, the walls need 4 courses, and the takeoff totals 87.2 linear feet — buy 11 eight-foot boards. You also need 2 hinges, 2 hydraulic lid arms, 1 hasp lock and about 132 exterior screws. The materials mode above recalculates the full list for any dimensions.

A 150-gallon-class box (61x25.4-in wind face, 10.76 sq ft of sail area) in a 70-mph gust sees about 12.54 psf of wind pressure — roughly 135 lb of lateral push. That exceeds half the weight of a lightly loaded box, so anchor it with L-brackets or ground screws, especially when empty. The placement mode above checks your exact setup.

Usually yes. A 250-lb loaded 150-gallon-class box on a 61x28.5-in footprint (12.07 sq ft) loads the deck at 20.7 lb per sq ft — well under the typical 40-psf residential deck rating. Problems start when several heavy boxes are clustered together or the deck is old; check the placement mode above with your numbers.

For a medium 90-gallon-class box, buying costs roughly $90-$200 while DIY in cedar runs about $247 in materials (about 96.5 linear feet of cedar at $2.20/ft plus $35 of hardware) — so buying usually wins at this size unless you want custom dimensions. DIY makes more sense for extra-large boxes, where retail runs $220-$430.