How much does baltic birch plywood weigh?

I am designing a truss dob and the balance calculations require me to know what the density of my building materials are... I have them all except baltic birch plywood.

Now I could buy some sheets and weigh them, but I can't know how much I need to buy until I know the weight :-<. And there are no scales at the lumber yard to measure beforehand... I asked.

Does anyone have a value for the density of baltic birch plywood?

Or am I going to have to cart a scale to the lumber yard?

Grant,

On my torque calc spreadsheet for my 12.5, I got that a square inch of 1/2 inch Baltic Birch weighs 0.010982143 pounds. A 10 inch x 10 inch square would weight about a pound.

I cannot remember at this time just how I arrived at that number. Won't swear to its accuracy now--maybe I'll go find a piece and measure again. I do know that my scope came out balanced just fine.

Alex