My insructable makes a crochet rug from old T shirts. The feel underfoot is fantastic! Look for shirts at thrift shops, especially Men's XL. Shirts should not have side seams or large vinyl designs.
Spread the T-shirt out on your cutting surface. I use an electric scissor to do my cutting. This has been a great tool for this process. I have tried a rotary cutter, but the layers were difficult to work through.

Cut off the bottom hem and the cut the shirt straight across right under the sleeves. This is the circular piece that will be used to make one long piece of yarn.

Materials:
13-14 t-shirts
3/4" crochet hook
Metal ruler
Scissors
Electric scissor

Step 1: Making Cuts in Fabric

Fold over the fabric as shown, top layer about two inches lower than the back layer. Cutting from the bottom go through all four layers in straight lines about 1.5" apart. A metal ruler can be used to get even spacing. Stop the cut just beyond the lower fold.

Step 2: Cutting Into One Long Strip

Once the strip cutting is completed, open up the shirt and extend it over one arm as shown.

Starting at the edge, use scissors to cut a diagonal line to release the first strip. Now cut a diagonal line between another two strips creating a spiral of the fabric. At the other end, release the final strip with a diagonal cut.

Step 3: Stretch the Yarn.

To turn into yarn, pull the strip along it's length and it will roll up on the edges. This is your yarn!

Step 4: Joining Yarn

When you add on another color to the rug, join the two pieces by fastening with a series of cuts at the joining ends. Thread the new color into the hole at the end of the yarn and pass it through the other end of this new color, once pulled all the way through the old and new will be spliced together.

Use this technique to make longer yarn from short strips as well. Parts of the back and front of the T=shirt can be cut into strips to be spliced together. Nothing but the hem, collar and sleeves go to waste.

Step 5: Crochet a Magic Ring or Circle

You will need a very big crochet hook (3/4") for this project. For a round rug, begin by making magic ring. There are plenty of Instructables on making the magic ring and crochet stitches so I am going to skip the how-to.

www.instructables.com/id/Crochet-Magic-Ring-Adjust

Or the other method:

Row 1: Chain 4, join, 5 SC.

Row 2: 10 SC.

Continue for Rows adding SC in different places to keep your work flat.

I use single crochet stitches for the continuing middle circle until it measures 13" in diameter. Use a slip stitch to taper the ending.

My magic ring: 7 SC crochet in the circle.
Row 2: ch 1, 2 HC in each SC
Row 3- : HC
More rows to create a 13" circle.

Step 6: Ending the Circle and Making Panels

Now begin the panel shapes to be added to the circle center. This rug takes nine panels to complete the rug.

Each panel is made individually and attached to the circle with more yarn.

Wedge panel around circle (x9)

Row 1: ch 9, 8 SC.

Row 2 & 3: 9 SC, adding SC in different places.

Row 4 & 5: 10 SC

Row 6 & 7: 11 SC.

Row 8: 12 SC.

Step 7: Attaching the Panels Around the Center Circle

To attach the wedges use a long piece of yarn and slip stick around the circle. I found it easier to do this with my fingers rather than with a needle. I left the sides open because I liked how it looked, but the sides of the wedges could be stitched together as well.

Step 8: Crochet a Trim to Complete the Rug

Begin a single crochet trim in the middle of an outer panel. The yarn will need to be a very long length to make it all the way around the rug. Add single crochet as needed to keep the rug flat.

End the trim where you began. Work to weave end yarns into the rug to hide them and trim excess.