Where yarn weight names come from: ply, DK and aran

A ply used to be a strand you could count

In 1847 Jane Gaugain’s The Lady’s Assistant, published in Edinburgh, asked for “four plies” and “eight plies” shaded Berlin wool in the same cape. The plies were strands, twisted together, so the number gave a knitter a fair idea of how thick the wool would be.

Ellen and C. A. Claydon spelled it out in their 1915 school manual, Knitting without “Specimens”: 2-ply describes “wools in which two threads only are twisted together”, 4-ply has four, 6-ply six. They added a warning that still holds. The threads themselves vary between makers, “so that all 4-ply wools are not of exactly the same thickness”.

Today the number is a size name. The New Zealand retailer Direct Sewing says knitters there “often talk about 4 ply, 8 ply and 12 ply”, while a British pattern says 4 ply, DK, aran or chunky. A UK 4 ply now means about 400m per 100g, the median in our UK yarn weights guide, whatever is inside the strand.

Double knitting started as a stitch

The oldest uses we could open have nothing to do with a yarn. The Ladies’ Knitting and Netting Book, printed in London in 1838 and now in the University of Southampton’s knitting reference library, gives “Double Knitting” as a stitch worked over “any even number of stitches”. Miss Lambert’s Hand-book of Needlework, in its 1842 edition, has the same stitch under “Double knitting for comforters”, to be worked in “four-thread fleecy”.

The wool arrives in the trade papers. In January 1906 Baldwin’s, the Halifax spinners, advertised in the Toronto trade journal Dry Goods Review under the heading “Latest novelties”: rug wool, feather wool “and double knitting wool”. By April 1906 a Baldwin’s advert in the same paper was selling Beehive Double Knitting Wool as “a grand yarn for warm garments, such as Socks, Stockings, Golf Hose, Gloves, Comforters and Combinations”, adding that “it is the same length and thickness as the best 3-ply Wheeling yarn, but is much stronger”. The advert was still running in 1907.

Between 1906 and 1918 the same name was matched to four different ply counts. A 1915 Canadian Red Cross Society knitting list, sent out with the University of Toronto’s appeal for its overseas hospital, asks for “double knitting wool, about 6 ply”. The Claydons in 1915 say double knitting is “often equal in thickness to 8-ply, though frequently four threads only, but of greater thickness”. And in March 1918 a shop advert in Victoria, British Columbia, sells “Baldwin’s Double Knitting Wool, 4-ply”. Ply had stopped being a reliable guide to thickness almost as soon as DK appeared.

So why “double”

None of the period sources we found explains the name. The nearest clue is the Claydons’ phrase: “The ‘Double Knitting’ wools, or ‘Double Fingerings’”. Fingering was a sock and stocking wool, and the Claydons recommend one Baldwin’s fingering for “socks, stockings, gloves”. Baldwin’s own 1906 list of wools opens with Scotch Fingering. Our reading is that double knitting was sold as a heavier fingering. That is an inference from the wording, not something a maker wrote down.

You’ll often read that DK is two strands of 4 ply. The idea has a long history: in 1975 Marshall Cavendish’s Introduction to Crochet said double knitting yarns were usually made from “four spun single threads” and were “virtually double the thickness of 4 ply yarns”. Direct Sewing says today that two ordinary 4 ply strands held together usually come out at about DK or 8 ply thickness, but “it is not guaranteed”. The metres tell a different story. Doubling the median 4 ply in our UK weights guide (400m per 100g) gives 200m per 100g. That is fewer metres than every one of the twelve DKs in that sample, the shortest being 208m, and close to the aran median of 190m.

Aran: a young jumper with an old story

The Aran Islands sit in Galway Bay, off the west of Ireland. The Victoria and Albert Museum’s regional knitting pages put it bluntly: “Contrary to popular belief, the typical cable-patterned Aran jumper is a 20th-century invention.” According to the V&A, the Congested Districts Board, set up in 1891, encouraged local people to knit for sale and trained knitters in stitches such as honeycomb, figure eight and double diamond. Instead of the dark, oiled wools used for fishermen’s jerseys, the islanders tried a “soft, thick, undyed yarn”. By the 1930s Aran knitting was sold to tourists in Dublin, and Vogue Knitting published an Aran pattern in 1956.

Siún Carden, writing from an anthropological point of view in the journal Costume in 2014, adds the names. Muriel Gahan opened The Country Shop in Dublin in 1930 as an outlet for the products of rural cottage industries, and commercial production seems to have begun in the late 1930s. From 1938 the German textile enthusiast Heinz Kiewe promoted a link between Aran stitches and ancient Celtic designs, a theory that, in Carden’s words, “became very influential, in spite of its spurious nature”.

The drowned fisherman story is a myth

The story goes that each Aran family knitted its own pattern, so a fisherman lost at sea could be identified by his jumper. Carden notes that J. M. Synge’s 1904 play Riders to the Sea is often cited as a possible seed. Read the play and the detail is smaller than the legend. The clothes come from “a drowned man in Donegal”, and his sister Nora knows him from “a plain stocking”: “It’s the second one of the third pair I knitted, and I put up three score stitches, and I dropped four of them.” A stitch count and a mistake, not a cable or a family design.

By 1962, Carden writes, the story had solidified. Pádraig Ó Síocháin’s Aran: Islands of Legend, in its 1962 edition, says of the Aran gansey that “it has always been an unfailing source of identification of Islandmen lost at sea”. Ó Síocháin founded the Galway Bay Company, which sold Aran knitwear, and Carden points out that the passage comes with the company’s contact details. The story is still told. The Aran Sweater Market’s history page says the sweaters “were often used to help identify bodies of fishermen washed up on the beach” (checked 3 October 2026). The V&A dates the jumper itself to the 20th century, and Carden treats the identification story as myth, so we do too.

How aran and chunky became sizes

Patons’ Book of Knitting and Crochet (1973), by Patience Horne and Stephen Bowden, says yarn in ready-wound balls instead of skeins “became general in the early 1950s”, and that “the use of double-knitting yarns increased sharply, not only because they were quicker to knit but because bulkier garments were becoming increasingly fashionable.” Its tension table for “the principal classic yarns” already runs from 2-ply to double double knitting.

In September 1959 an Eaton’s advert in a Belleville, Ontario, newspaper offered “4-ply ‘Aran’ Wool”, with Aran still in quotation marks and a ply count attached. In 1961 the London machine-knitting magazine Modern Knitting used “chunky” both ways: for a garment, as in “a lightweight ‘chunky’” and “if you knit a chunky it will see you through”, and for yarn, in a pattern for Penelope Bingo Chunky Crepe. By 1975 Marshall Cavendish’s Introduction to Crochet was calling “Chunky and double double knitting yarns” extra thick yarns, and in 1982 Shelagh Hollingworth’s Complete Book of Traditional Aran Knitting, which carries a foreword by Kiewe, wrote of “the thick Aran quality yarns”. A place name and an adjective had become yarn sizes.

Worsted: a Norfolk village in American patterns

Worsted comes from a place, not a ply count. Worstead is a village in north Norfolk. The county’s Norfolk Heritage Explorer says its church of St Mary appears to have been begun in the late 14th century, largely with money from “the thriving wool business”, at a time when cloth was made across Norfolk, “particularly after the influx of Flemish weavers”. It adds that “Worstead itself gave its name to a cloth type which is still produced today.”

In British knitting the word stayed close to the mills: the Claydons’ 1915 list includes Fleming, Reid & Co. of the Worsted Mills, Greenock, and Baldwin’s “Super Fingering Worsted” in 2, 3, 4 and 5-ply. In American patterns it became a size. The Craft Yarn Council puts “Worsted, Afghan, Aran” together in its Medium category, number 4. As our UK yarn weights guide notes, a worsted can run a little lighter than an aran, so the shared number doesn’t make them the same yarn.

From six numbers to eight, and what it means for substitution

The Craft Yarn Council’s Standards and Guidelines are dated April 2003. Its first yarn weight chart, captured by the Wayback Machine in May 2003, had six categories: Sock, Fingering, Baby; Sport, Baby; DK, Light Worsted; Worsted, Afghan, Aran; Chunky, Craft, Rug; and Bulky, Roving. A capture from 21 September 2007 still shows six. One from 2 October 2007 adds a category 0 for lace. Today the chart runs from 0 (Lace) to 7 (Jumbo), and the page announces a Size 8 (checked 3 October 2026).

A century of names leaves you with words that mean roughly the right thing. DK has been called 3-ply-thick, 4-ply, about 6-ply and 8-ply-thick, and today’s UK DKs still range from 208m to 334m per 100g. The figure that means the same thing on every ball band is length for weight. When you swap yarns, put the pattern’s yarn and your new one into the yarn substitution calculator, and read our guide to substituting yarn by metres per 100g for why two yarns with the same name can need different ball counts.

Common questions

Sources and scope

• www.heritage.norfolk.gov.uk/record-details
• archive.org/details/krl00376333
• archive.org/details/ladysassistantfo03gaug
• www.gutenberg.org/cache/epub/994/pg994.txt
• archive.org/details/dgrstyle1906toro
• archive.org/details/dgrstyle1907toro
• archive.org/details/sim_nursing-times_1914-10-31_10_496
• archive.org/details/presidentfalconer37006
• archive.org/details/cu31924003593427
• archive.org/details/dailycolonist60y81uvic
• archive.org/details/handbookofneedle00lamb
• web.archive.org/web/20071027131353/http://www.vam.ac.uk/collections/fashion/features/knitting/regional/index.html
• pureadmin.qub.ac.uk/ws/files/9812437/postprint_Carden_aran.docx
• archive.org/details/aranislandsofleg0000paos
• www.aran.com/history-of-aran-sweaters
• archive.org/details/patonsbookofknit0000horn
• archive.org/details/intelligencer-september-1959
• archive.org/details/modern-knitting-1961-feb-mar
• archive.org/details/introductiontocr0000unse_l3k1
• archive.org/details/completebookoftr0000holl
• web.archive.org/web/20030515051334/http://www.yarnstandards.com:80/
• web.archive.org/web/20030517065232/http://www.yarnstandards.com:80/weight.html
• web.archive.org/web/20070921000628/http://www.yarnstandards.com/weight.html
• web.archive.org/web/20071002134651/http://www.yarnstandards.com/weight.html
• www.craftyarncouncil.com/standards/yarn-weight-system
• www.directsewing.co.nz/blogs/news/nz-yarn-weight-guide-4-ply-8-ply-dk-aran-chunky-and-international-conversions
• hazelloop.com/guides/uk-yarn-weights-explained/

Sources checked 3 October 2026. Label facts come from the linked references; worked purchase examples and arithmetic are our own illustrations.