Compelled by craft-infatuation, I sliced up some old dinge-y tshirts according the the various helpful tutorials that are out there. The tutorials might be useful for, say, making crochet bowls.
They are not helpful for making the quantity necessary for a rug. I love the way it looks now, but it was a somewhat miserable slog to get enough material for the giant rug I had in mind. From trial and error, how to make an enormous amount of t-shirt yarn.
1. Buy a lot of jersey fabric. A lot. I ended up using four king sheet size sets (I know.) because it was the most cost-effective fabric I could find. If you live in Philly, don’t go to Fabric Row for this one. The only white jersey I found was $24/yard. I don’t know how many yards are in a king-sized sheet set, but at $34/set it barely matters.
2. Cut all hems and elastic out of or away from your sheets. You may be tempted to try to use your seam ripper because you feel guilty about waste, but doing so will turn this arduous project into an even greater time-suck. If you feel really guilty, put leftovers in your ‘scraps for stuffing’ bag for when you finally make that ottoman you’ve pinned like eight times already.
3. Open your windows. This shiz gets dusty.
4. Either cut or rip one-inch strips. Doing this will take you an ungodly amount of time, so I would recommend:
4.5. Taking your entire sheet. Folding it in half lengthwise. Fold it nearly in half again, but let the edges peak out about 8 inches. Keep folding from the bottom to the top two layers of fabric.
4.63. You can use scissors, or if you are blessed by your own craft supplies buying compulsion, break out your cutting matt and rotary cutter. Slice through the folded sheet at one-inch intervals. This will give you many one-inch strips that are folded over on themselves. I cannot tell you how pleased I was with myself for having bought the rotary cutter after the first six balls of yarn. 
5. At the edges of your strips, cut slits. This way you can join the yarn together without making knots.
6. Join the yarn using numero 3 of this tutorial.
7. Stretch the strips so they get ropey. Now you understand why the commercially available brands are named after pasta.
Netflix in the background: Seasons 1 and 2 of the Tudors. You can take that judgment somewhere else.
wasted weekends 
I’m getting slightly concerned – it appears you’ve flown by me in your sewing skills when i’ve been sewing since high school. PS – I just got a rotary cutter – it’s the GREATEST!
Love this! How many rugs were you able to make with the 4 sets?
Hahah! Just the one! I’m not so sure I’d do this a second time it was so labor intensive.
Thank God you wrote this. My symptoms have been progressing… cut up old t- shirts and made a few bowls… asked hubby to donate old t-shirts to more projects… feeling a strong desire to purchase a rotary cutter and cutting mat… Yep – I definitely have caught the ‘t-shirt yarn crochet a million projects’ fever.
I didn’t even know I was heading towards crocheting a rug until I saw that cute thing in the background of the picture. Now I need a zillion yards of t-shirt yarn.
Thanks for the tips. I will be heading for some king sheets now.
Oh gosh! Well, I hope it’s helpful! In full disclosure this project completely (completely.) cured me of the desire to do a t-shirt yarn crochet project again. But! The rug has survived a move and a couple household wares purges, so it does have staying power.
do you have to use the jersey knit material? or do you think just a plain cotton/polyester blend sheet would work as well?
Hey! For these purposes you need a knit, not a woven, material. If you use woven, it will end up looking quite rag-rug-y, and I don’t think it will lend itself very well to crocheting in the first place. Hope that helps!
I actually did something similar to this with some stretchy t-shirt like fabric I got pretty cheap at walmart. i folded the whole piece of fabric in half and sewed down one side, to basically make a giant tube. Then I used that wonderful rotary cutter and sliced it up just like those tutorials that teach you to make one continuous ball of yarn from a t-shirt. was still totally tedeious and I had some blisters by the end but with the sewing there was no need to link all the pieces together after cutting. Thanks for posting this!
how much yarn can you get per yard of fabric?
Hm, good question. I️ didn’t measure, but I️ got a roughly 5’ diameter circular rug out of it.