An urban planter box full of soil usually weighs between about 100 kg and 500 kg (220–1,100 lb), but there is no single answer. The total weight is the empty planter plus the soil, and the soil weight depends on volume, moisture, and soil type. A simple estimate is: volume in liters × soil bulk density in kg per liter. Potting mix is relatively light, often around 0.4–0.7 kg per liter. Moist topsoil is much heavier, typically around 1.2–1.6 kg per liter, and saturated soil can approach 1.8–2.0 kg per liter.
For example, a 200-liter planter filled with potting mix at 0.6 kg per liter contains about 120 kg of soil. If the empty box weighs 30 kg, the full weight is around 150 kg. The same 200-liter box filled with moist topsoil at 1.4 kg per liter would contain about 280 kg of soil, making the total roughly 310 kg. A smaller 40-liter balcony box with potting mix might weigh only 30–40 kg when full, while a large 500-liter street planter could exceed 700 kg with wet topsoil.
The planter material matters less than the soil and water, but it still adds weight. Timber, fiberglass, metal, and concrete boxes can vary widely. Drainage also matters: a box that holds water will be significantly heavier than one that drains freely. Before filling a rooftop, balcony, or raised courtyard planter, check the load capacity of the structure and choose a lightweight potting mix rather than dense garden soil where possible. As a practical rule, assume a full urban planter box will weigh at least three to five times the weight of the empty box, and plan for extra weight after rain.