A 4ply is a fingering weight yarn, while a 3ply is a light fingering weight yarn. If you knit the 3ply yarn with the same number of stitches as the 4ply yarn, your knitting will come out slightly smaller. If you are working with shawls, it will not usually make a difference since they have no fit. Both 3ply and 4ply are middle-weight yarns, so it is possible that if you use the same needle size, your finished item should almost look the same size. Knowing your chosen yarn’s weight before starting a knitting project is essential. The yarn weight will determine how your knitting will turn out when you finish your project. The term yarn weight may be misleading as it does not refer to the actual weight of the yarn. It defines the yarn more based on its thickness. Thick yarns are described as heavy yarns, while thin yarns are light. Usually, the thickness of the yarn is the most popular way that differentiates between the different types of yarn. You can find the yarn weight on the ball band, and the suggested needle size is appropriate for the yarn weight. Knitting patterns commonly indicate the yarn weight to get the best results for your knitting project. You must be aware that there are different ways that these yarn weights are called depending on the country using them. The US uses numbers to identify yarn weights that the Craft Yarn Council of America has formalized. Below is a list of the US Yarn Weight Categories and Standards and their comparison to other yarn weight categories used by other countries. Lace Weight The lace weight yarn is the lightest yarn weight used for knitting. Yarns belonging to this category include thread, soft fingering yarn, cobweb yarn, etc. You can use these lightweight yarns for lace knitting. Lace weight is delicate and prone to breakage and tangling. It is usually used for knitting doilies, bibs, and other small and fragile items. It is usually not the type of yarn you would want to use when starting with knitting. You can use 1.5mm to 2.25mm needles on a lacey thread. The lace weight yarn is 1 – 3ply in the UK, AUS, and NZ. Super Fine The next category is superfine or fingering weight which is still a delicate type of yarn. It is equivalent to the 4ply threads in UK and Australia. The superfine wool looks almost similar to lace weight, so you can also use it to knit delicate and fragile items like baby clothes, socks, and shawls. You can knit superfine yarns using 1, 2, or 3 US needles. If you substitute this type of yarn for lace weight, use the suitable needle sizes to achieve the right feel for your finished knitting. Super Fine yarns are also called “sock weight” or “baby weight yarns,” as socks and baby apparel is the most common knitting done using this type of yarn. Fine/Sport Weight Yarn The Sport Weight or Fine yarn belongs to category 2 in the US. It does not have an equivalent in the UK, but it is almost the same as 5ply. Fine yarn is also called “baby” in some countries as it can produce fabric great for baby clothes, socks, and thicker lace patterns. It uses US size 3-5 needles. For some knitters, it is better to knit lace because it works faster and gives a better design definition. DK/Light Weight Double Knit or Lightweight yarn is one of the most common yarn weights. It is pretty similar to sport weight yarn but slightly heavier. It is an ideal material for knitting scarves, hats, sweaters, dresses, etc. It is almost the same yarn weight of 8ply in Australia and New Zealand. You can use two threads of DK yarns together as an alternative for worsted weight yarn. The DK yarn works quickly and is not so fragile, so it is an ideal yarn material for newbie knitters. You can use a US-size six needle for the DK yarn. Worsted/Aran Worsted or medium weight yarn is the most popular and mainly used yarn weight in knitting. This medium-weight yarn is called Aran in the UK. Worsted weight yarn uses US size 6-9 needles. It is a versatile yarn as it is not too delicate yet not too heavy also. You can knit different items with medium-weight yarn, such as hats, scarves, sweaters, and blankets. Worsted weight yarn is slightly thinner than the UK Aran yarn. But both are similar to the 10ply yarns of Australia and New Zealand. The Worsted yarn is a favorite among newbies and expert knitters because it gives excellent stitch definition and works quickly. Bulky Bulky yarns are called Chunky in the UK and 12ply in Australia. The ply in the name does not necessarily mean the number of strands combined to form the thread. It only designates the category level of the yarn. Bulky yarns are perfect for newbie knitters as it needs big and wide needles to create large and loose stitches. Bulky yarns produce knitting projects that are thick and warm, like blankets, hats, and scarves. Bulky and Chunky yarn can differ a lot in thickness, so it can be tricky to substitute a bulky yarn in a pattern. Sometimes, it is tough to identify the bulky yarns as some yarn companies brand all the yarns heavier than worsted as Bulky weight yarns. It would still be safer to knit a swatch to confirm if your yarn can replace. Super Bulky Super Bulky weight yarns are thicker than Bulky and use the US size 11 needles or bigger. They are known as Super Chunky in the UK and 14ply in Australia and New Zealand. Category 6 yarns are quick to finish and create super warm, big blankets, sweaters, rugs, and hats. Jumbo The Jumbo or Roving Weight Yarn is the thickest yarn weight you can find. It is usually used to knit giant rugs, blankets, and other arm knitting projects. The Jumbo yarn also requires larger needles, such as the US size 17 needles or larger. The different categories have different names and can be confusing because there are no “official” yarn categories. Here is a table comparing the different yarn weights and various knitting projects you can make. US UK AU Common Names Used Needle Size Possible Knitting Projects 0 Lace 1 ply 2 ply Thread, Cobweb, Fingering 1.25 – 3 mm Delicate lace, baby garments 1 Super Fine 2 ply 3 ply Fingering, Sock, Baby 1.25 – 3.5 mm 2 Fine 4 ply 5 ply Sport, Baby 3.25 – 4mm Baby clothes, heavier socks, lightweight tops 3 Light DK 8 ply Jumper, Light, Worsted 4 – 5mm Ideal for most garments 4 Medium Aran 10 ply Worsted, Afghan 4.5 – 6 mm Outdoor and warm clothing, fishermen’s jumpers 5 Bulky Chunky 12 -14 ply Heavy, Worsted, Craft, Rug 5mm – 8mm Outdoor wear, winter jumpers, oversized garments 6 Super Bulky Super Chunky 16 ply Roving 8mm – 12mm Furnishings, jackets, blankets 7 Jumbo Super Chunky 20 ply Roving 12mm+ Eye-catching scarves, coats, cozy cushions and throw pillow cases