Things You'll Need
Dressmaker's white chalk
Although spending money on a new tank top is easy, you can repurpose your old shirts for free by cutting off the sleeves. Depending on the design of the shirt, you can easily remove its sleeves to convert it into a sleeveless top, as long as you have a sharp pair of shears to cut cleanly through the fabric. For a polished look, measure the sleeves prior to cutting them, so they'll be even.
Lay your shirt on a flat surface and adjust a seam gauge to 1 1/2 inches. Use the seam gauge to measure 1 1/2 inches from the edge of the armhole.
Mark the 1 1/2 point on the sleeve with dressmaker's white chalk. The mark indicates where you will cut the sleeve.
Lay the ruler against the mark so that it is parallel with the armhole seam. Draw a line against the ruler with the chalk, which will help you remember where to cut.
Pierce the shirt with a pin through both sides of the sleeve, near the top of the armhole edge, then push the sharp edge of the pin back up to secure the fabric. Smooth the sleeve down the ensure the fabric is aligned.
Pierce the bottom of the armhole edge with a pin through both sides of the fabric, to keep it in place.
Cut along the chalk line with sharp fabric shears.
Measure the other sleeve equally with the seam gauge and repeat the marking, pinning and cutting process.
Launder the shirt as instructed on the garment's tag to wash off the chalk.