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Handspun Yarn Calculator (Wraps per Inch, Yarn Weight, Grist, Twist & Fibre Needed)

Identify a handspun or mystery yarn's weight category from wraps per inch, work out its grist in yards per pound and metres per 100 g from a weighed sample, the plied twist angle and TPI for a balanced yarn, and how much fibre to spin for a project.

Wraps per inch (plied yarn, relaxed)

Sample weight

Sample length

Plies

Singles twist

Project needs

Fibre loss in prep & spinning

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How it works

grist (yd/lb) = sample yards ÷ sample lb; m/100 g = sample m ÷ g × 100 · WPI classes: lace 18+, fingering 14–18, sport 12–14, DK 11–12, worsted 9–11, bulky 6–8, super bulky ≤ 6 · balanced ply TPI ≈ ⅔ × singles TPI (2-ply), 0.55× (3-ply) · fibre = project yards ÷ (yd/g) ÷ (1 − loss)

Handspun has no ball band, so spinners describe yarn with two measurements: wraps per inch, which maps to the familiar weight categories, and grist — yards per pound or metres per 100 g — which says how dense the yarn is and therefore how much a project will weigh. Together they let you buy the right amount of fibre and match a commercial pattern. Twist is the third dimension: plying in the opposite direction with roughly two-thirds of the singles twist gives a balanced two-ply that hangs straight; more twist for hard-wearing yarn, less for loft.

Worked example

A 2-ply that wraps 12 per inch is DK weight. If 24 m of it weighs 10 g, its grist is 2.4 m/g — 240 m/100 g or about 1,190 yd/lb, typical for the WPI. Singles spun at 3.5 TPI want plying at about 2.3 TPI for balance, a twist angle of about 32°. A 1,200-yard project in this yarn weighs about 457 g, so with 15% loss spin from about 540 g of fibre — buy 600 g.

Frequently asked questions

How do I measure WPI properly?

Let a length relax (unwound from the bobbin, twist settled), wrap it around a ruler or WPI gauge so the wraps just touch without gaps or squeezing, and count over two inches and halve. Measure the washed, finished yarn — it usually plumps up one or two WPI.

What grist should I aim for?

Match a commercial yarn you like: worsted wool is about 900–1,100 yd/lb, DK 1,100–1,300, fingering 1,800–2,200. A high-grist yarn at the same WPI is lofty and warm; a low-grist one is dense and drapey. Grist matters more than WPI for how far a skein goes.

How do I know the ply twist is balanced?

Take a freshly plied length, let it hang in a loop: if it hangs straight it is balanced; if it twists on itself in the ply direction it is over-plied, in the singles direction under-plied. Wash and snap the skein before judging finished yarn.

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