On most quilts, charm square blocks are cut into 5 inches, which translates to 4.5 inches after the seam is sewn. Coin blocks are 2.5-by-5 inches, which is 2-by-4.5 inches once the seams are sewn.
A twin quilt that measures 63-by-88 inches and is made with 5-inch charm squares requires 280 charm squares. The quilter divides the width, 63 inches, by sewn charm square, 4.5 inches, and does the same for the length, 88 inches. The two numbers this yields are multiplied together to get the number of charm squares needed for the quilt, which is 280 blocks.
Coins require calculating sashing, as well. The sashing is cut at 3.5 inches and finishes at 3 inches. To measure the number of coins needed, the quilter has to figure out how many columns of each are needed. A queen quilt measures 84-by-92 inches, so simple math calculates the number of columns for width, which are 11 columns of coins and 12 columns of sashes.
For length, 6 inches is subtracted from the top and bottom sashing, then the remaining 86 inches is divided by the size of the finished coin, which equals 43 coins. If there are 43 coins and 11 columns, then 473 coins are needed for the quilt. Measuring the yardage of sashing needed requires a quilt calculator, which can be found online. In this example, the yardage required has been rounded up to 5 yards.