Step 1: Grab a favorite t-shirt or one with a fit that you really like.
Step 2: Lay your old shirt on top of your fabric or paper (if you are making a pattern that you can reuse), along the fold like this.
Step 3: Cut or trace around the t-shirt, leaving about '5/8-1' seam allowance as you cut. If you're nervous about potentially cutting your old shirt, use a pencil or some marking chalk to draw around the shirt first. (The pink lines represent the tracing around the shirt)
Step 4: Repeat the top step for the back of the shirt. (Blue lines are the tracing of the back)
Step 5: Place the two pieces together and sew along the shoulder seams. (Orange lines are where you will sew)
Step 6: Sew side seams together (once again, the orange lines).
Step 7: Neckline
This is my favorite tutorial for a t-shirt neck band, so, instead of re-inventing the wheel, click here to access the tutorial.
Here's the equation if you already get the general gist of it.
Neckline x .15 =X (Total neckline)-X = the length of fabric you need for neckline
Step 8: Hems
You will be finishing your sleeve edges and the bottom of your shirt. I recommend using a double needle to finish off your shirt, as it's easy and looks professional. You can use this fabulous tutorial for detailed instructions!
Ta da! Now you have your very own basic T!!!