There are three things you can do to tighten a cotton shirt: shrink, stick or tie it. If your shirt is made of cotton, you can't shrink it too much. Sewing is probably the best option, as long as you know how. If you are a woman, you can tie the extra fabric together and let your shirt get a whole new personality, but you may find this to be very revealing. If all else fails, change it.
Put on a shirt like a glove.
Adjust your washer for a small charge at the highest possible water temperature. If the water in your home never gets too hot, you can add boiling water to the washer.
Allow the washer to fill.
Add detergent as usual.
Put your shirt in the washing machine and leave it on until the washing process is complete. Do not add any other clothes.
Put your shirt with the highest temperature set in the dryer.
Turn off the tumble dryer if the shirt dries on the bones.
Allow the shirt to rest in the dryer until the fabric has cooled down.
Determine how many inches you want your shirt to be stricter.
Turn the shirt out.
Take the shirt off on a flat surface so that there are no wrinkles.
Draw two lines, each parallel to the side seams of the shirt. The distance between the lines and the seams must correspond to the number of inches you want to get from the shirt. So if you want the shirt to be 2 inches shorter, the distance between each line and the seam should be 1 inch.
Insert six to ten pins along each line and go through the entire shirt.
Cut the side seams from your shirt.
Sew your new seams while removing the needles.
Put on your shirt.
Stretch the fabric around the trunk and concentrate around the bone.
Wrap the excess material with a rubber band to form a tail.
Put the tail under the shirt and lift it up until the rubber band is covered.