If you have ever stood in a yarn shop holding two skeins that look roughly the same size and found yourself completely unable to tell which one is right for your project, this guide is for you.
Yarn weight is one of those terms that sounds more technical than it actually is. It does not refer to how heavy a skein is. It refers to how thick the strand of yarn is, and therefore how many stitches fit into a given measurement of knitting. Once you understand that, everything else follows fairly naturally.
So here is the whole thing, explained plainly, with a note on what we stock at Prosper for each weight along the way.
First: why does this even matter?
Every knitting pattern is written with a specific yarn weight in mind. The pattern assumes your yarn will produce a certain number of stitches per 10cm, and that assumption informs every calculation in the pattern from stitch count to finished dimensions. Use a thicker yarn than specified and your finished garment will be larger than expected. Use a thinner yarn and it will come out smaller.
This is why yarn weight is the first thing to check when you are choosing yarn for a pattern. It is more important than colour, more important than fibre, and more important than price. Get the weight right and everything else becomes much easier.
There is also a NZ-specific wrinkle worth knowing about. In New Zealand and Australia we traditionally use a ply system: 2ply, 4ply, 8ply, 10ply, 12ply. The rest of the world tends to use named categories: Lace, Fingering, DK, Worsted, Bulky. Ravelry, which most knitters use to find patterns, shows both. A pattern might call for DK / 8 ply (11 wpi) in exactly the Ravelry format. Knowing how to read that means you can shop with confidence anywhere in the world.
A note on WPI
WPI stands for wraps per inch. It is the most reliable way to check a yarn's weight when you are unsure. Wrap the yarn around a ruler without overlapping and count how many wraps fit in one inch. The number tells you the weight category. Each section below includes the standard WPI range so you can check any yarn you are working with, not just ours.
The weights, one by one
Here are the yarn weight categories from finest to thickest, with the NZ ply name leading and the international equivalent alongside, exactly as Ravelry formats them.
Lace / 2 ply Lace (18+ wpi)
WPI: 18+
Needle: 2.0 to 2.5mm
Gauge (10cm): 32 to 40 stitches
Lace weight is the finest yarn you will commonly encounter in knitting. It is thin and produces a fabric of extraordinary delicacy. Lace patterns rely on this fineness to create the open, airy quality that gives them their name. Shawls are the most natural home for lace weight, though it is also used for delicate accessories and lightweight scarves. The knitting is slow and requires attention, but the finished results are genuinely breathtaking.
Best for: Shawls, held-alongside projects, delicate scarves and wraps
Our pick: Mint 70% Kid Mohair, 30% Silk. Our most ethereal yarn. Mint is typically held alongside another yarn rather than used alone, adding a luminous halo and warmth without bulk. One skein goes an extraordinary distance.
4 ply / Fingering Fingering (14 to 18 wpi)
WPI: 14 to 18
Needle: 2.5 to 3.25mm
Gauge (10cm): 28 to 32 stitches
4ply is the traditional sock knitting weight and for good reason. It is fine enough to produce a fabric with excellent stitch definition, durable enough to withstand the wear of a shoe, and just substantial enough to knit at a pace that feels rewarding. But it is not only for socks. Shawls, lightweight jumpers, fine accessories and baby garments all work beautifully at 4ply. The finished fabric has a clarity and precision that heavier weights cannot match.
Best for: Socks, shawls, lightweight jumpers, baby garments, fine accessories
Our pick: Precious 70% Merino, 20% Cashmere, 10% Recycled Nylon. 425 metres per 100g. The cashmere makes this one feel indulgent from the moment you pick it up. We love it for shawls, fine garments and anything that will be worn next to skin.
A quick note on Ravelry's formatting here: you will often see patterns listed as 4 ply / Fingering (14 wpi). That is the same weight. Some patterns will specify sock weight, which sits within the fingering category. They are interchangeable for most purposes.
DK / 8 ply DK (11 wpi)
WPI: 11
Needle: 3.5 to 4.5mm
Gauge (10cm): 21 to 24 stitches
DK stands for double knitting, and it is arguably the most versatile weight in knitting. It is fine enough to produce detailed fabric and fast enough to make a sweater in a reasonable timeframe. Most beginner patterns are written in DK for exactly this reason. You will find jumpers, cardigans, hats, mittens, shawls and countless other projects at this weight. If you are choosing a yarn to learn with, DK is almost always the right call.
Best for: Jumpers, cardigans, hats, mittens, shawls, most beginner projects
Our pick: Prosper DK is100% Superwash Merino and Epic is 100% NZ wool for those who prefer a non-superwash option with beautiful stitch definition. Both are 8 ply. Both are excellent. This is our most popular weight category at Prosper, and it is the one we would always suggest for a first project. If you are not sure where to begin, our Prosper DK is a good place to start. Smooth, consistent, and available in a wide range of colourways.
Worsted / 10 ply Worsted (9 wpi)
WPI: 9
Needle: 4.5 to 5.5mm
Gauge (10cm): 18 to 20 stitches
Worsted weight is where knitting starts to feel genuinely quick. The stitches are substantial and satisfying, the fabric grows fast, and the finished result has a density and warmth that lighter weights cannot quite match. It is a wonderful choice for outdoor garments, thick cardigans, cushion covers and anything that needs to be properly, seriously warm. The larger needle size also makes this a more forgiving weight for beginners who are still finding their tension.
Best for: Heavy cardigans, outdoor garments, cushion covers, warm accessories
Our pick: Bossy 100% Lambswool. Lambswool has a naturally springy quality that holds its shape beautifully over time. Bossy is our worsted weight option and it is exactly what the name suggests: confident, warm and built to last.
You might also see 10ply referred to as Aran weight in some patterns, particularly older British ones. Aran sits between worsted and bulky, with a WPI of around 8. If a pattern calls for Aran, a 10ply yarn will generally work well, though it is worth knitting a gauge swatch first.
Bulky / Super Bulky Bulky (7 wpi and below)
WPI: 7 and below
Needle: 6.0mm and above
Gauge (10cm): 14 stitches and below
Bulky yarn is the fastest way to have a finished knit in your hands. A hat in bulky weight can be done in an evening. A cowl in a weekend. The large needles and thick yarn mean the fabric grows visibly with every row, which is enormously satisfying when you are learning or when you simply want results quickly. The finished fabric is thick, warm and has a relaxed, tactile quality that is wonderful for cosy winter pieces.
Best for: Quick hats, cowls, blankets, scarves, fast gifts
Our pick: Westie 100% Superwash Merino in a generous bulky weight. Westie is soft enough to wear next to skin despite its thickness, which is not something all bulky yarns can claim. Our most immediately satisfying yarn to knit with.
How to find the right weight for a pattern
Most patterns tell you the yarn weight on the first page, usually alongside a recommended needle size and a gauge measurement. Here is how to read those three pieces of information together.
- Yarn weight tells you which category to shop in. If the pattern says DK / 8 ply, you need a DK weight yarn.
- Needle size is a starting guide. The pattern will suggest a needle size that typically produces the right gauge in that weight. But this is not absolute. Everyone knits differently.
- Gauge is the number that actually matters. Gauge tells you how many stitches and rows should fill a 10cm square at the correct tension. Knit a swatch, measure it, and adjust your needle size until your gauge matches the pattern. This step saves a great deal of frustration later.
One thing we always tell people in our lessons: the gauge swatch is not optional. I know it feels like a delay before the real knitting begins, but it is the single most useful thing you can do before casting on a garment. A few cm's of difference in gauge translates to a garment that is several sizes too large or too small.
What if a pattern lists two weights?
You will sometimes see patterns that offer options, for example a jumper available in both DK and Worsted with different stitch counts for each. This is great because it gives you flexibility. Choose the version that matches the yarn you want to use, or the one that suits the gauge you typically knit at.
You will also occasionally see patterns that ask you to hold two yarns together, for example a 4ply held alongside a lace weight mohair. This is a common technique that produces a DK-ish weight with a beautiful halo. Our Sophie Shawl kit uses exactly this approach: Beaut Merino Singles held with Mint mohair. The combination is genuinely lovely and the two yarns behave as one as you knit.
Still not sure? Come and ask us.
This is genuinely one of the things we love most about having our studio. You can bring your pattern in, hold different yarns against it, and we will help you work out what you need. No purchase required. We would rather you leave with the right yarn than leave with the wrong one.
We run beginner knitting lessons in our Ponsonby studio too, and yarn weight is one of the first things we cover. If you would like to book a space, you can register your interest here.
Browse all our yarn by weight From 2ply Mint all the way through to bulky Westie, our full yarn range is online and ships across NZ and worldwide. Shop all Prosper Yarn.
Happy knitting. And if you ever find yourself standing in a yarn shop genuinely unable to tell whether something is an 8ply or a 10ply, just wrap it around a ruler. That is what the ruler is for.
