There are many variables in determining how much weight plywood can hold. Variables involved are the thickness of the plywood, the span it is to cover, the depth, and whether it is fixed or floating. Other factors are whether or not it has an edging strip and what the material of the stripping is, the thickness of the edging strip, and the width of the strip. Another variable is the load distribution, whether it is center load or uniform. There is a calculator, The Sagulator, to help you determine how much weight your plywood project will hold at the WoodBin website.