How do you measure twist angle?

By Amelia © April 13, 2026

I much prefer to measure twist angle in my yarn instead of twists per inch.

Part of this stems from my unwillingness to count treadles when using a wheel, perhaps because neither my spindles or my espinners have a treadle. The other part is that twist angle has the same impact on yarn whether I spin thick or thin, while twists per inch (TPI) change as wraps per inch change, to get the same feel.

I am a huge fan of Mabel Ross - to the point of having two copies of her book Essentials of Yarn Design for Handspinners, and one of each of her others, Encyclopedia of Hand Spinning, Essentials of Hand Spinning, and Hand Spinners' Workbook: Fancy Yarns. (All links are affiliate links - I may benefit from you using them to make your next purchase.) She has lovely tables in her books of WPI, treadle counts, TPI, and twist angle. I distilled it down for myself, filtered through my experience, to:

• 15° → very soft fluffy yarn - usable but easy to split when knitting
• 25° → medium knitting yarn - great for hats and scarves
• 35° → durable yarn - lowest twist I like for socks
• 45° → crepe yarn - high twist weaving yarn that will crinkle the fabric woven to a balanced sett

You can buy specialty tools for measuring twist angle, or simply use a protractor. I've done both. In fact, Mabel Ross's book has a twist angle tool printed on cardstock in the back. The tools are handy because they contain the typical twist range, so you aren't going to measure in a way that mis-reports twist angle as 75°.

Protractors, however, are much easier to find in your local school supply aisle or online, like the one I found here. I can display it on my phone when I want to measure twist angle. With the protractor, I line my yarn up on the 0 line at the flat bottom, and keep it parallel to the 0 line as I slide it across toward the 90° on the other side.

The angle lines on the protractor tell you what twist they measure - those slanted like the middle of the S measure S-twist (counter-clockwise twist) and the other half, slanted like the middle of the Z measure Z-twist (clockwise twist). What about the 90° mark? I like to jest that it is for measuring corespun, as that has the fiber wrapping a core, perpendicular to the length of the yarn.

In the series of pictures that follows, you see me moving the yarn across to measure the ply twist, which here is S-twist. I am looking for the angle line that matches the angle of the strands twisting around each other.

If you agree with me, you will say this twine (it's what I had to hand for these images...) has a twist angle between 25° and 30°

I would use the other half of the protractor for Z twist.

I recently posted on twist in singles vs. twist in yarn plied from them. I usually use a ply-back to see the ply twist and help me decide on the appropriate amount of singles twist, rather than trying to directly measure twist angle in singles. I invite you to check out your current spin against a protractor and free yourself up from counting treadles.

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© April 13, 2026 by Ask The Bellwether, posted at http://askthebellwether.com/