I've made 4 t-shirt quilts, one for each of my grand daughters when they went away to college. I use my 12.5 inch ruler and made them all that size. You can see through the ruler and it's easy to center the logo. I ironed on a fusible light weight facing on each t-shirt. (ironed on the facing before cutting the squares. I also used a 2.5 inch sashing plus a border. I put 4 across and 5 down. It uses 20 t-shirts and they turned out to be a perfect size for their beds in the dorm.