Step 1: Find an Old T-shirt and Template
I went thrift shopping and came across this awesome t shirt today and awhile back I bought this black tanktop and I loved the fit. I will be using this as a template, it's not necessary though.
Step 2: Plan Your Cuts
Remember measure twice, cut once! Lay your template on top of your t shirt and see where the armpit and shoulder seams lines up. Use a pen or marker to mark the spot.
Step 3: If You Don't Have a Template Do This.
There are two ways you can do this. 1: wear the t shirt and mark where you want the arm holes to end. (How low the holes are going to be) and then fold and cut. 2: fold the t shirt in half and measure one inch below where the arm pit seams meet each other. Mark, fold and cut.
Step 4: Time to Cut!
Fold your shirt in half and cut where you marked. Then cut off the collar of the shirt. ( if you don't like it on, I prefer mine cut off.) Stretch out all the place you have cut by tugging on them to make sure all the cut stay. Then you're done! Enjoy your new tank top!