It would appear from a 12 in. block for a King Size quilt (108 x 108) it will take 81 blocks (9 in a row across and 9 rows). From the Log Cabin Trim Tool Two there are 8 rows to the block, and each strip would need to be 2 inches wide so it would finish at the 12 inches, using the 1/4 inch seam.
If you make the center a 2-1/2" square AND and five LIGHT value fabrics of your choice, cut in 1-1/2" widths, plus five DARK value fabrics, cut in the same widths ...lengths of each strip will vary in length 2-1/2" to 12-1/2"--to be safe, cut both lights and darks as long as you can.
It is easy to calculate how much of each piece you will need once you identify what type of Log Cabin you want to make. Both ways you will need 81 pieces of each.