Short answer: A typical urban planter box that measures about 24 by 12 by 12 inches and holds roughly 1.7 to 2 cubic feet of soil usually weighs between 80 and 120 pounds after it is filled with moist potting mix and watered. Smaller balcony boxes often weigh 50 to 80 pounds, while larger boxes can weigh 130 to 200 pounds or more. If the container is made of ceramic, terracotta, or concrete, the total can easily exceed 250 to 400 pounds.
The urban planter box weight depends on two main parts: the empty container and the soil. A plastic or resin planter of this size may weigh 5 to 15 pounds empty; wood can be 20 to 40 pounds; ceramic or concrete can be 40 to 100 pounds or more. Filled planter weight also depends on soil volume and moisture. One cubic foot of dry potting mix weighs about 20 to 30 pounds. The same cubic foot can weigh 30 to 40 pounds when moist and 40 to 50 pounds when saturated. Topsoil or compost is heavier, often 40 to 60 pounds per cubic foot when wet.
To estimate soil weight per cubic foot for your own setup, multiply the soil volume in cubic feet by the soil density in pounds per cubic foot, then add the empty container weight. For example, 2 cubic feet of wet potting mix at 35 pounds per cubic foot equals 70 pounds of soil. Add a 10-pound resin container, and the filled planter is about 80 pounds. A 3-cubic-foot wood box with 100 pounds of wet soil and a 30-pound frame totals roughly 130 pounds.
Because water is heavy and soil holds water, a planter box weight can increase significantly after rain or watering. This matters for balcony planter load limits on balconies, roof terraces, and fire escapes. Check the load limit, keep large planters near load-bearing walls, use lightweight potting mix instead of garden soil, ensure drainage, and consider casters or pot feet for movable planters.
As a practical rule, a typical urban planter box filled with soil weighs about 80 to 150 pounds. Smaller ones can be 50 to 80 pounds; larger or heavier-material planters can be 200 pounds or more.