A Mens Size Small T-shirt
A Pencil or Marking Tool
Turn your t-shirt inside out, fold it in half. Cut the lower part of each sleeve off.
With your ruler mark a diagonal line on your shirt with the lowest part in the middle of the shirt. then cut the bottom section off and discard.
Make a small cut beside the collar of the shirt. for the back cut following just below the collar line. For the front I was going for a casual t-shirt so kept my cut a big higher. To keep your cut even you can fold the t-shirt in half making sure to keep the back half clear of your scissors. Start your cut at the lowest point cutting up wards to meet with your original neckline cut. Remember you can always cut off more so start with a modest cut.