As I folded my clothes, I realized this polo had seen better days. But that is just when they get so soft and cozy. Looking at the size (it is a kids 14-16 don't judge the boys are cut longer than womens sizes) it looked about perfect for my throw pillows. I have 4 throw pillows that have also seen better days and while I have big plans for them in the future they are now acting as floor pillows since their covers are not removable. So long story short...add a large button and about 6 inches if ribbon to serve as the loop. Tuck the shirt in and around the pillow envelope style button the neck pop the collar and 5 minutes later I have a soft, washable pillow cover that matches my duvet cover and is cute and preppy all at the same time.
For reference the pillows are 20 inches square and my shirt is the perfect width to fit without being loose and sloppy so I would recommend a womens M or boys L if you plan to outfit a similar sized pillow. I have 3 more pillows but am not ready to sacrafice any more polos just yet.