I don't vouch for the 'ease' of this method, but this is what I do:
I take my thread in question, and wrap it around a pencil. You don't want to pull too tight, or mash together too hard, but your strands should lay nicely next to each other with no bunching or spacing. However many strands fit in an inch is the wraps per inch (or WPI) of that particular crochet thread.
Now, there are a lot of charts which give wraps per inch ranges for YARN (ewwww!) but I was hard-pressed to find any concerning crochet thread. They all stop at what they call lace weight yarn and say any with more than 18 wraps per inch falls in that category! To a thread crocheter however, there is a big difference between 18 wraps and 32 wraps! So I figured I better put my thoughts here just in case someone else is looking for this information too.
My favorite brand for my crochet projects is Red Heart and the Red Heart owned Aunt Lydia's, and I was only able to measure what I had on hand, so this isn't as complete as I would like it to be. As I get more data I will improve my little chart here. Different brands will yield slightly different results, and I did not take multiple measurements to account for any tension differences in wrapping, so this is just an estimate here!
Some places I have seen wraps measured per centimeter, so I have included that here too.
This information will also be useful if you wish to try to figure out how to substitute perle cotton or embroidery floss for the crochet thread.
Aunt Lydia's Fashion Crochet Thread, Size 3 Lustrous and soft crochet thread, suitable for apparel and home decor | 24 wraps per inch | 9 wraps per centimeter |
Red Heart Fashion Crochet Thread, Size 5 A little heavier than bedspread weight, this thread is perfect for apparel, accessories and home décor. | 28 wpi | 11 wpcm |
Aunt Lydia's Classic Crochet Thread, Size 10 The most common and popular, size 10 crochet thread, offers many options for your favorite projects in a variety of colors! | 32 wpi | 13 wpcm |
Aunt Lydia's Fine Crochet Thread, Size 20 Extra fine & fine crochet thread for delicate crochet work, such as doilies, table runners, home décor and accessories. | 50 wpi | 20 wpcm |
Aunt Lydia's Extra Fine Crochet Thread, Size 30 Extra fine & fine crochet thread for delicate crochet work, such as doilies, table runners, home décor and accessories. | 60 wpi | 24 wpcm |
I would love to hear your experiences and feedback with this chart.