You found the perfect pattern, you open the materials list, and it says: circular needles, 3 mm [US2½]. You open your needle case, and the sizes go from US 2 straight to US 3. No 2½ anywhere.
This happens a lot with Scandinavian patterns, and PetiteKnit's patterns are a well-known example: Vega Sweater, Jenny Blouse and Ivy Tee all ask for a 3 mm needle. In this guide I will go through what a 3 mm needle is in US sizes, why your set doesn't have it, and four ways to knit the pattern anyway.
Is there a US size for a 3 mm needle?
Not really. In the needle size table of the Craft Yarn Council, the sizes around it look like this:
- 2.75 mm - US 2
- 3 mm - no US size at all, the field is empty
- 3.25 mm - US 3
So 3 mm sits exactly between US 2 and US 3, 0.25 mm away from each. Some designers and needle brands call it US 2½, and this is what PetiteKnit writes in her patterns: "3 mm [US2½]". But it is not a standard US size, and this is why many sets don't include it.
The Craft Yarn Council also gives good advice here: rely on the millimeter size, because the number systems vary from company to company. The millimeters are the real measurement.
Why your needle set skips it
Scandinavian patterns think in millimeters, often in half-millimeter steps. PetiteKnit's patterns, for example, use 2.5 mm (US 1½), 3 mm (US 2½), 3.5 mm (US 4), 4 mm (US 6) and 4.5 mm (US 7). Many interchangeable sets are built around the US numbers instead:
- The ChiaoGoo Twist Small set has seven sizes: 2.75 mm (US 2), 3.25 mm (US 3), 3.5 mm (US 4), 3.75 mm (US 5), 4 mm (US 6), 4.5 mm (US 7) and 5 mm (US 8). It jumps right over 3 mm.
- The HiyaHiya Small set has exactly the same seven sizes.
- Some sets don't go that small at all. The Lykke set starts at 3.5 mm (US 4), and so does the KnitPro Symfonie Deluxe set.
If you want to know why I still think an interchangeable set is worth it, I talk about it in my top 10 knitting tools.
First, check what the 3 mm needle is for
Look at the gauge line of the pattern. It tells you which needle the gauge is measured on.
If the gauge is on a bigger needle, the 3 mm is only for the ribbing and the edges. The No Frills Sweater is like that: needles 3 mm and 4 mm (US 6), and the gauge is given on the 4 mm. Here you can relax. Use your 2.75 mm (US 2) for a firmer edge, or your 3.25 mm (US 3) if your ribbing tends to be tight. The size of the sweater doesn't depend on it.
If the gauge is on the 3 mm needle, it matters more, because now this needle decides the size of the whole garment. Some examples from PetiteKnit:
- Vega Sweater: 23 stitches x 36 rows = 10 x 10 cm / 4 x 4" in stockinette on a 3 mm needle, in Double Sunday from Sandnes Garn. The ribbed neckline is on 2.5 mm (US 1½).
- Jenny Blouse: 36 stitches x 34 rows = 10 x 10 cm / 4 x 4" in the smock pattern on a 3 mm needle.
- Ivy Tee: 28 stitches x 40 rows = 10 x 10 cm / 4 x 4" in stockinette on a 3 mm needle.
For patterns like these, here are your options.
Option 1: swatch with the needles you have
The needle size in a pattern is the size that the designer needed to get the gauge. You might need a different one anyway! What you have to match is the gauge, not the number on the needle.
So before you buy anything, knit two swatches: one on 2.75 mm (US 2) and one on 3.25 mm (US 3). Wash and block them the way you will treat the finished garment, and count. If you have never made a swatch before, here is my gauge swatch tutorial, step by step.
- Too many stitches in 10 cm / 4" means your stitches are too small, and you need a bigger needle.
- Too few stitches in 10 cm / 4" means your stitches are too big, and you need a smaller needle.
If you are a tight knitter, the 3.25 mm (US 3) may well give you exactly the gauge of the pattern. If you are a loose knitter, the 2.75 mm (US 2) might. In both cases the problem is solved, and you didn't need a 3 mm needle at all.
Option 2: change the needle material
This one is less known. The material of the needle changes your gauge, even when the size in millimeters stays the same.
Jillian Moreno tested this for Modern Daily Knitting. With the same yarn and the same needle size she got 4.5 stitches per inch on bamboo needles, 4 on textured metal needles, and just over 3.5 on smooth metal needles. The reason is friction: wood and bamboo hold on to the yarn, so the stitches come out tighter. On slick metal the stitches come out looser.
So if your swatch is almost there:
- A bit too loose on a metal 3.25 mm (US 3)? Try a wooden or bamboo needle in the same size.
- A bit too tight on a wooden 2.75 mm (US 2)? Try a metal needle in the same size.
Option 3: change the yarn
You can also come from the other side. Instead of looking for the needle that fits the yarn, look for a yarn that gives the pattern gauge on a needle you already own.
The logic is simple. On the same needle, a slightly thinner yarn makes slightly smaller stitches, so you get more stitches in 10 cm / 4". A slightly thicker yarn gives you fewer.
- Your swatch on 3.25 mm (US 3) has too few stitches? A slightly thinner yarn will bring you closer to the gauge.
- Your swatch on 2.75 mm (US 2) has too many stitches? A slightly thicker yarn will.
How do you find "slightly thinner"? Compare the meters (or yards) per 50 g. The Vega Sweater, for example, suggests Double Sunday, which has 108 m / 118 yds in 50 g. A yarn of the same fiber with more meters in 50 g is thinner, and one with fewer meters is thicker. Stay close to the original. We are talking about small steps inside the same yarn weight, not about swapping DK for fingering.
Two things to keep in mind:
- The fabric changes too. You can get almost any gauge with almost any yarn, the question is whether you like the fabric. A thinner yarn on a bigger needle is airier and has more drape. A thicker yarn on a smaller needle is denser.
- A different fiber behaves differently after washing. So again: swatch, wash, measure.
This option is especially nice if you planned to substitute the yarn anyway.
Option 4: just buy a 3 mm needle
Sometimes the simplest answer is the best one. You don't need a new set for that.
- Separate tips. ChiaoGoo sells 3 mm (US 2.5) tips on their own, and they fit the same small cables as the 2.75 mm (US 2) to 5 mm (US 8) tips of the set. If you have a different set, check whether the brand sells single tips in 3 mm.
- A fixed circular needle in 3 mm. For a sweater, an 80 cm / 32" cord works for the body and, with magic loop, for the sleeves as well.
If you like Scandinavian designers, you will probably use this needle more than once.
What about the 2.5 mm needle for the ribbing?
Vega and Jenny also ask for a 2.5 mm (US 1½) needle, and this size is even harder to find. It is not in the Craft Yarn Council table at all, and the sets that start at 2.75 mm (US 2) don't have it.
The ribbing doesn't decide the size of the garment, so don't worry too much. What matters is that it is smaller than your main needle. The pattern uses a needle that is 0.5 mm smaller for the ribbing, so you can keep that gap:
- Main fabric on 3.25 mm (US 3) → ribbing on 2.75 mm (US 2).
- Main fabric on 2.75 mm (US 2) → ribbing on 2.25 mm (US 1).
The short version
- Check the gauge line. If the 3 mm is only for the ribbing, use 2.75 mm (US 2) or 3.25 mm (US 3) and move on.
- If the gauge is on the 3 mm, swatch on 2.75 mm (US 2) and 3.25 mm (US 3) first. One of them might simply work.
- Almost there? Try a different needle material, or a slightly thinner or thicker yarn.
- Or buy a pair of 3 mm tips or a fixed 3 mm circular.
And in all cases: trust the millimeters, not the US number.
New to all this? Start with what you need to make your first project.
Have you run into the missing 3 mm needle? Tell me how you solved it on Instagram. I would be curious to know!
