Do you hate threading your needle, making that knot, running out of floss in the middle of row of stitches? If so, you may be tempted to cut yourself a super long piece of floss and start embroidering.
Does the length of your floss really matter? Yes, it does! When you cut a length of floss it should be roughly 12 inches long. First, it's easy to manage. Second and more importantly, it prevents the floss from degrading before you finish the length. Floss gets worn as it is pulled up and down through the fabric. It loses it's shine and becomes slightly fluffy. If you cut your floss too long, these two problems can show up in your finished embroidery.
12 inches is a great length for cotton embroidery floss. You'll have to experiment with the length when using other types of floss. For example, crewel wool tends to degrade even faster.
A good way to measure a length without pulling out your measuring tape is by holding the floss in one hand and pulling it down to your elbow with the other. That will give you roughly 12 inches. Take a look at the illustration above!