For a rooftop terrace, the filled weight of a typical planter from our planter box factory usually falls between 170 and 240 lb (about 77–109 kg) for our most popular 24 x 12 x 12 in rectangular fiberglass or composite planter. The empty planter weighs roughly 20–30 lb. Its internal volume is about 2.0 cu ft. Moist, settled potting mix generally weighs 75–100 lb per cu ft, so the soil alone is about 150–200 lb. Add 10–20 lb for drainage gravel, brackets, and a small plant, and the ready-to-use total is commonly 180–240 lb. In dry, lightweight mix it may be closer to 160–190 lb; after heavy rain or with dense mineral soil, it can exceed 250 lb.

Size changes the answer quickly. A compact 18 x 12 x 12 in planter (1.5 cu ft) often weighs 130–180 lb filled. A medium 30 x 15 x 15 in planter (about 3.9 cu ft) commonly reaches 330–430 lb. A large 36 x 18 x 18 in planter (6.75 cu ft) can weigh 550–750 lb filled, depending on soil and drainage. Because rooftop capacity is limited, use saturated weight—not dry weight—when planning.

To estimate any model, use: filled weight = empty planter weight + (soil volume in cu ft x soil weight per cu ft) + drainage and plant allowance. Our factory can supply the empty weight, volume, and recommended soil fill line for each planter box. For rooftop terraces, choose lightweight composite or fiberglass containers, use a drainage layer, and place heavier planters over load-bearing beams. If the roof has strict load limits, consult a structural engineer before filling large boxes. As a practical guide, a typical 24 x 12 x 12 in factory planter filled with moist potting soil weighs about 180–240 lb, but always confirm the exact SKU and soil mix.