For those following along, we began with plastic bag knitting

 (https://rosalindhughes.wordpress.com/2011/06/17/a-plastic-story/ ),

moved on to a t-shirt cat mat (https://rosalindhughes.wordpress.com/2011/07/18/more-recycled-knitting/),

then a t-shirt bag, for which I promised a “proper” pattern once I’d repeated the feat.

Here’s the pattern I used for this slightly smaller than but similarly proportioned to the original t-shirt bag. It took one t-shirt and one pillowcase pretending to be a t-shirt to complete (the original bag took 3-and-a-bit t-shirts).

Notes: I used a circular, US10.5 needle. 16″ long. Gauge is not important and will depend greatly on the weight of your t-shirt “yarn.” For a bag, aim for a tight (but not uncomfortable to knit) fabric. Adjust needle size to accommodate your yarn and knitting style and the size of the bag will vary but the shape should still be good.

Cast on 32 stitches, place marker and join to knit in the round.
Knit 2 rounds.
K8, m1, repeat 4 times to end of round (36sts)
Knit 4 rounds.
K9, m1, repeat to end of round (40sts)
Knit 4 rounds
K10, m1, repeat to end of round (44 sts)
Knit 12 rounds
K9, k2tog, repeat to end (40sts)
Knit 2 rounds
K8, k2tog, repeat to end (36sts)
Knit 1 round
K7, k2tog, repeat to end (32sts)
K6, k2tog, repeat to end (28 sts)
To finish:
Turn bag inside out. Hold both needle points together and divide stitches in half between both sides of the circular needle. With a spare straight needle, cast off 2 stitches at a time (1 from each side). Fasten off. Turn bag right side out. Add a strap recycled/reused from your material of choice.

If you prefer a circular pattern all the way to the bottom, continue reducing as established til 16 stitches remain. Draw yarn through remaining stitches, pull tight and secure. Add strap.