The first thing you need to do is remove the sleeves (save them!) and cut straight across the top of the shirt.

My shirt is already inside out. I didn't want to mark the front.

Turn the shirt inside out, if you haven't already.

Mark the middle of the shirt, and use it to center 1/2 of your UNDERBUST measurement.

Here's all that pesky measuring . . .

Extend the midline to help guide you. Measure the thinnest part of the waist, and the distance between that measurement and the underbust measurement to make your next horizontal line. The line will be 1/2 the waist measurement.

Measure your hip, and the distance between that and the waist measurement for the last horizontal line. This line will be 1/2 the hip measurement.

At this point, you can measure how long you want the dress, and shorten it. I left mine the original length for now.

Pin it together, and cut it out. Since I used my actual measurements, I cut outside the lines for my seam allowance.

Sew it up!

Ok, so I forgot to take a pic of this part. Bear with me.

Cut open the sleeves and lay them flat. Measure your overbust measurement across the cuff. Measure the distance from overbust to underbust from top to bottom, and cut the excess off the bottom. Then Measure your underbust along the bottom. You can measure your bust measurement across the middle.

What you end up wIth sort of looks like an oval. Again, sorry for no pics, but you can see it in the other pics.

Match up the bottom edge to the rest of the dress, right sides together. Pin and sew.

Technically you could be done here, for a tube dress. But I don't trust gravity, so I added some ties to the front.

It was at this point that I thought my dress was too long, but then I cut it too short. So I added a ruffle.

I cut the bottom 3 or 4 inches off a much larger t-shirt. I sewed a basting stitch ( the pink line) to gather it, pinned it, right sides together, and sewed it on!

And now I have a bad ass dress!!