Hi John,

I can show you how to estimate the number. I expect there will be some partial blocks and hence some wastage so I can't give you an exact number.

I expect the 28 and 48 are feet. That is $28 \times 12 = 336$ inches by $48 \times 12 = 576$ inches. You didn't say what are the dimensions of a block. Measure the length of a block in inches. Divide 336 by the length of the block to find the number of blocks needed for 1 course on the 28 foot side. Double this to find the number of blocks needed for 1 course on the two 28 foot sides. Perform the same operation to find the of blocks needed for 1 course on the two 48 foot sides. Add these two numbers and multiply by 10 since you want the walls to be 10 courses high.

This will give you a number which is too large as I expect you want some doors and windows.

Harley