T-shirts that definitely won't be worn again (irreversibly damaged or stained) are best to use for this project, as it provides a crafty extension to t-shirt life (much better than destroying it forever by throwing in the bin). If the t-shirt has nothing wrong with it, probably keep it as a t-shirt. Someone else will definitely want it, even if you don't.
Time needed - 1 hour
Equipment - t-shirt, good scissors, straight edge/ruler, pen/pencil, flat surface
Lay chosen t-shirt on a flat surface and if you want to knit it immediately also locate chunky knitting needles. I think these pictured are a size 10.
Fold t-shirt in half (sleeve to sleeve )
Cut off the top of the t-shirt from underneath the sleeves, leaving a square. This is what you'll use.
(save the sleeves and neckline surplus for another project)
With a ruler/straight edge and pen/pencil, draw vertical lines 2cms apart.
Cut into each of these lines, cutting from the fold up to the seams, BUT...
ONLY CUT THROUGH ONE SEAM, don't cut any strips actually off. By leaving one seam uncut it means all your strips stay connected.
When finished cutting on all lines, fold it out. It should still all be connected by that one seam you didn't cut through.
Fold open that one remaining seam. Arrange the strips neatly on both sides and lay flat. I used an ironing board to help with this part, so that strips on both sides can dangle over the edges of the board and keep out of the way.
Cut DIAGONALLY from one side to the other.
(Apologies for the basic photoshopping)
...and wrap into a ball and Ta-dah!! One ball of t-shirt yarn.
The size of t-shirt will alter how much yarn is produced. This large blue t-shirt produced 25m.
T-shirt yarn knitting joy