According to Windsor Plywood, a 4-foot by 8-foot by 1/2-inch sheet of plywood weighs roughly 46 pounds. This weight varies depending on the type of wood used, the type and amount of glue used, and whether or not the plywood has absorbed excess moisture.
The estimate of 46 pounds assumes that the plywood is dry, composed of soft wood, made in North America and of good quality. A change in any of these variables changes the overall plywood weight. The weight of a sheet of plywood does not denote whether it is more or less sturdy than a similar sized sheet with a different weight.