How to knit a hat, part 2: Gauge and size

How to knit and measure a gauge swatch

I’m reminded why I always shy away from writing about swatching: There are a thousand caveats. I’ve kept this as brief as possible but the fact is it’s an important subject and I want to do it minimum viable justice. It’s a long post. So first let’s talk quickly about whether you need to swatch for a hat, and then I’ll launch into the whole how-to.

The answer to “Do I have to swatch for a hat?” is the same as for anything: Only if you want it to fit. A lot of people don’t swatch for hats, and I’m in this camp. (And it has led to multiple “learning experiences.”) Often you’re trying to squeeze a hat out of single skein and don’t want to give any of it to a swatch. Or you just really want to cast on and knit the hat, and figure you’ll find someone it fits when it’s done. Or you accept ripping as an integral part of knitting, so you let the hat be its own swatch and are prepared to rip and restart if need be.

My friend Rachel was elated to have knitted her first hat last week, and over the weekend I got a series of deflated text messages from her. She had soaked her hat, which was all ribbing, and now that the ribbing had relaxed it was way too big. I told her the hat-that-don’t-fit situation is a rite of passage. She replied plainly, “It’s very discouraging,” and yes, it surely is. But it can be avoided simply by knitting and measuring a gauge swatch first.


A swatch is a square of fabric that puts you in control of your outcome. The point of knitting a swatch is to understand how the fabric will behave and to establish your gauge — to see if your stitches are the same size as the pattern drafter’s stitches, and thus whether your finished item will be the same size as the pattern indicates. So the most important thing about knitting a swatch is that it has to be a nearly exact replica of the thing you mean to knit. Therefore:

• Use the exact yarn
No two are the same; a dyed yarn will even behave differently than its undyed version

• Use the exact needles
Your gauge will likely be different if, e.g., you swatch with bamboo and knit with metal

• Use the exact method
Swatch flat if knitting flat; swatch in the round if knitting in the round


In knitting patterns, gauge is usually stated either in stockinette stitch or in the stitch pattern used for the item in question, and it’s measured over 4 inches but might be stated as the 4-inch measurement or divided by 4 for the 1-inch measurement. I.e., “20 stitches and 28 rows over 4 inches” is the same as “5 stitches and 7 rows per inch.” You measure 4 inches rather than 1 to make sure you’re getting an accurate count of fractional stitches in a given inch, which can add up to quite a lot over the span of a garment.

In order to measure 4 inches, you need at least that many stitches — ideally more. The best swatch is a big swatch (especially if you really want to know if you like the fabric), but at bare minimum, you don’t want to be measuring edge stitches in your 4 inches. Sticking with that 5 sts/inch example above, you know that 20 sts will be about 4 inches (depending on whether you are a looser or tighter knitter), so you want to pad it to give yourself margin for differences and for measuring. I would cast on at least 25 stitches, but again, preferably more. And unless you already know yourself to be a loose or tight knitter, start with whatever needle size the pattern recommends.

Many people like to put a garter-stitch border around their swatches because it looks nice and because stockinette will roll. Others believe (especially if your swatch is small) that the difference in stitch and row gauge between garter stitch and stockinette will affect your measurements. I’m a purist, so I keep my swatches to only the pattern stitch and don’t put a border on them.

Again, if the item you’ll be knitting is knitted in the round, you must swatch in the round, and vice versa. Most people’s gauge varies between their knits and their purls, so if you knit a stockinette swatch flat (knitting on one side and purling on the other), your gauge will be different than when you knit stockinette in the round (knitting every stitch). And vice versa. Garter stitch worked flat is all knits; worked in the round it’s a combination of knits and purls. Here’s a good tutorial on swatching in the round — it’s much easier than it sounds.


Here’s the frustrating truth: Some patterns list unblocked gauge and others list blocked gauge. Some don’t specify. (If you don’t know what blocking is, click here.) What you really need to know is: A) is the fabric going to change when you block it? and B) what are the final measurements?

So once you’ve got at least 4 inches of fabric — wide and tall — bind off loosely and measure your swatch. Write it down. Then block it however you will block your garment. If you don’t intend to ever wash your garment, okey doke, you’re done. If you intend to wash your garment by hand, go ahead and soak your swatch. If it’s machine-washable yarn and you intend to use the machine, machine wash your swatch. Then lay it flat to dry.

If you’ve done as I’ve done and knitted a plain stockinette swatch, you’ll have an annoying little rolled up worm of fabric. If you pin the edges while it dries, as pictured, it will flatten out, making it easier to work with and to measure. But you want to know the natural size of the fabric, so don’t stretch it when pinning. Once it’s dry, measure it again.

I’m pretty sure it was in Pam Allen’s “Knitting for Dummies” where I once saw the suggestion that you put a pin in the swatch at the 0- and 4-inch marks before counting. I’d never done that until I did for the sake of these photos, and that’s pretty sharp, so you should do that. First line up your ruler horizontally across the bottom of one row of stitches, with the zero point of the ruler at the outer edge of a stitch, as shown. (A knit stitch, which we’re looking at here, looks like a V. We’re counting Vs.) Put a pin at 0 and at 4. Now count how many stitches are between the pins, and that’s your 4-inch stitch gauge. (Divide by 4 for how many stitches per inch.) Now position the ruler vertically alongside a column of stitches. Again, place two pins and count the stitches between them. You can see here I have 20.5 stitches and 30 rows over 4 inches, or 5.125 stitches and 7.5 rows per inch.

Remember, I’ve knitted a stockinette swatch for this example because that’s the most common case. But your swatch should be in whatever stitch the pattern calls for where it states the gauge.


Assuming you want your garment to match the pattern dimensions, you need to match the pattern gauge. If your stitches are too big (fewer of them per inch), try again on a smaller needle. If your stitches are too small (more of them per inch), try a larger needle. Make whatever adjustments are needed until you’ve matched the pattern’s gauge.

If it’s not important to you to match the pattern dimensions, you can always choose to knit at a different gauge, just make sure you know how different your gauge is and how much of a difference that will make to the finished dimensions. With hats, it’s fairly common to tweak gauge to tweak the size. I have a big head and most hat pattern dimensions are too small for my liking, so I look at every hat pattern and think “can I knit that in the next heavier weight of yarn on a needle one size bigger?” (E.g. if it’s a worsted-weight hat on 7s, I’m inclined to knit it in aran weight on 8s.)

Gauge is a function of yarn weight, needle size and the knitter’s tension, any or all three of which can be varied to get the desired results. It’s delayed gratification — casting on a swatch when you want to be casting on a hat — but you’re that much more likely to be gratified by the hat you wind up with.


PREVIOUSLY: How to knit a hat, part 1: Anatomy lessons

40 thoughts on “How to knit a hat, part 2: Gauge and size

  1. This is a wonderful resource. Thank you for taking the time. After 2 years of knitting all manner of shawls, hats, cowls, I’m casting on for my first garment so I will follow this carefully. I especially appreciate the details about how to count the rows.n

  2. I can testify to the error of not washing a swatch. It was not a happy surprise when I did block the sweater. I just took a class with Joji and she suggests casting on 50% more stitches than gauge for the width of a swatch and at least 4″ in length.

  3. Techknitting has a brilliant way to check gauge in the round by knitting flat. She discusses the method with the loop of yarn on the back and then comes up with a “loops” method. If you aren’t familiar with her, check her out. She is posting infrequently these days as she is writing a book, but there is more than a wealth of information already in her index.

    • I’ll second the shout-out for techknitting’s site. It is loaded with ingenious techniques for some of the most common knitting issues. Her in-depth explorations may be a bit advanced for beginning knitters, but reading her site has helped me to understand the depth of knitting skills and how even advanced knitters are constantly updating and refining their techniques.

  4. Despite your tredpidation, Karen, I think you’ve absolutely nailed your “minimum viable” goal, and more. Clear and concise, and that’s a real accomplishment with this topic. Thanks!

    I’m a strong believer in measuring in fractions of an inch (or centimeter), not fractions of a stitch. Length units are a well-defined concept, but stitch fractions are murkier. Yarn twist and knitting style can make stockinette Vs asymmetrical, and when knitting with heavier weight yarn, even a quarter stitch can be a relevant quantity — but not an easily measured one!

    So instead of marking 4 inches with pins, I mark some whole number of stitches (for example, the number that gives 4 inches according to the pattern gauge), and measure how many fractional inches (or cm) they occupy. When working in inches, I usually measure to the nearest 1/8th of an inch. I do the same for row gauge: mark a whole number of rows, and measure in fractional length units. Just as simple as the more commonly taught method, and satisfies my precision-loving-scientist mind.

  5. No wonder patterns seem to have different dimensions than me. I have been swatching all wrong.
    Thank you for explaining it so well.

  6. Thank you for this. I’m a new knitter and I hate swatching just because I feel like I’d be wasting yarn. I’m knitting an unswatched sweater as I read this, in fact, and the thought occurred to me that if I finish this sweater and it doesn’t fit me, I may be so discouraged that I stop knitting for awhile!

  7. Thank you for a good text. Making a swatch is important especially when you use different yarns from suggested yarns. I have a question. When I make a swatch, sometimes horizental stitches are the same as a pattern, but vertical ones not, usually too small. What should I do to deal with?

    • It’s common to get stitch gauge and not get row gauge. You can either just account for it wherever it would matter (like a sweater yoke) by working more rows to get the right dimensions. Or if you’re knitting flat, you can try using a larger needle on the WS rows.

  8. I am so glad you mentioned that if you are knitting in the round you should swatch in the round. Many people forget how drastically their gauge can change from knitting flat to knitting in the round. I know by my own experience (meaning errors) that when I do a body flat I almost always need to go down one needle size if I’m to work the sleeve in the round. My gauge can vary by up to half a stitch per inch which for a hat or anything you want to fit really, could make for a disappointing project. I hope your friend has a better experience after swatching for her next hat! :)

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  10. Thank you so much for this blogpost! My friends never swatch yarn so in the beginning I didnt do this either, untill I had to unravel a cardigan like 4 times. I was using the wrong size needle.

    I was struggling with my swatches as the ends curl up, good idea to knit (garter) the ends, great tip!

    • If you put a garter edge on it, just make sure your swatch is big enough that you can measure far enough away from the garter edge to not get any distortion. Like I said, I prefer to knit only the stitch pattern cited and block it flat before measuring.

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  21. When patterns list how much yarn you’ll need for a certain project, are they including yarn that’s supposed to be for a swatch? Or just listing how much you’ll need for the project itself? I never know how much extra yarn I’ll need in order to make a swatch and test gauge. Do you have any suggestions? Thanks!

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  29. Great info. Very well explained. The gauge called for in my pattern is 22 stitches x 40 rows = 4 inches on size 5 needles. I am now starting my fourth swatch using size 8 needles. Is it possible that my knitting is so far off from the needle size the pattern is calling for?

    • Anything is possible! Sounds like the pattern designer was a loose knitter and you’re a really tight knitter. All that matters is matching gauge, and it sounds like you’re doing the right thing to get there!

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