The Knitting Fiend

For today’s blog: “How to knit the correct length sleeves, 101″.

Yesterday, I mentioned that I once followed a pattern slavishly, and knit sleeves that were way to long for the wearer. Today, I’m going to discuss how to figure out how long to knit the sleeves sleeves to fit the wearer. Obviously, I use this information to calculate patterns from scratch. However, this information is also useful if you are just trying to check the sleeve length on a published patter.

It’s pretty obvious to most people that your armlength affects the proper length for sleeves. Above and to the left, I show how to measure my arm.¹ To measure your arm length, find the bone at the top of your shoulder, your wrist and the point of your elbow. Holding your arm bent, run a tape measure from the top of your shoulder, along your elbow down to your wrist.

Write that number down. Arm Length = 21″.

Now, if you knit a sweater with a fitted sleeve cap, and you’ll probably find this is the correct length for a knitted sleeve. But you know what? The knitted sleeve won’t be that long for any other sweater style!

To figure out the correct sleeve length for other sweater styles you also need to measure your shoulder width. I put sticky dots on each of my shoulder bones and measured from dot to dot. (By the way, I used one of those dots when I measured my arm length.)

Write that number down: Shoulder Width = 14″.

Now, do a simple calculation to determine the “full sleeve length” for the wearer.

Full sleeve length = Arm Length + Shoulder Width/2 = 21″ + 14″ /2 = 28″.


To the left you can see the full sleeve length shown on a drop sleeve sweater. To measure it, fold a sweater in half along the back, and place one end of a tape measure at the center back then measure to the cuff fold. When I knit someone a sweater, I make sure the full sleeve length on the sweater matches their body’s full sleeve length.

To give an example, let’s say I knit a sweater for me. My shoulders are 14″ and my arms are 21″. My full sleeve length is 28″. But, if I knit a drop sleeve sweater, I like the chest to measure 40″ around. When I lay that knitted flat the “sweater shoulders” are 40″/ 2 = 20″ across; because the front and back widths are each 20″.

To design a sweater with a “full sleeve length” of 28″, I calculate”:

Full Sleeve Length – “Sweater Shoulder Width”/2 = “Knitted Sleeve Length” or 28″ – 20″/2 = 18″.

That’s right, the sleeves are 18″ long. That’s 3″ less than the arm length of 21″. If I knit them 21″ long, the sleeves would have been long, long, long!

Now, I’d like to make a practical suggestion. If you design a sweater for a wearer and are uncertain about their exact measurements, plan for a fold back ribbed cuff . Do this by adding 1″ to the sleeve length and make the cuff ribbing a bit long.

Why? Well, first of all, you might miss your stitch gauge by 5%². In that case, a 40″ wide sweater may end up only 38″ wide. Let’s say you’d planned plenty of ease, and 38″ is still wide enough for the wearer, so you aren’t going to rip out your whole sweater. Well, there is another problem. Unless you pick up the sleeves and knit them a bit longer, this loss of shoulder width will steal 1/2″ from your sleeve length!

If you added a fold back cuff, the sleeves will still be long enough. The wearer can just fold them back a little less than you’d planned. Of course, you might have gotten a larger gauge, and the sweater body ends up too wide. That would make the sleeve will be a bit too long; but the wearer can fold the cuffs a bit more. Plus, fold back elastic ribbed cuffs tend to hold the sleeves up nicely. This permit the wearer to wear them sort of “bloused” up. Up to 1″ of blousing is generally tolerable; 3″ is not.

Now what if the sweater is a raglan? Well, in this case, the full sleeve length still needs to match the measurement from the center back, and down along the sleeve. If you the end of the cuffs to hit you at the wrist when your elbows are bent, you need the full sleeve length of the sweater to match the full sleeve length of the wearer.

People who use my pattern generartors to knit top down raglans will notice that the text will alert you to a whole bunch or measurements including the width across the back neck, the depth of the yoke and the lower sleeve length, which is the length of the knitted sleeve before you join it to knit the body and sleeves together. Guess what?

Full sleeve length = “back neck width”/2 + [ "depth of yoke" + "lower sleeve length" ]

After all, the quantity in brackets is the sleeve length measured from the top of the sleeve to the cuff!

I should warn you though, if you check sleeve lengths on pattern schematics, the “back neck width as wornd” is a bit difficult to determine by reading the schematic. The real back neck width just a tiny bit wider than the width the back neck on a raglan schematic. This is because when you assemble the sweater, the top of the sleeve ads about 1/2″ to 1/4″ to the back neck depth! (Heck, I’m exaggerating. Sometimes it’s only 1/8″.)

Now, if you want worry about this, go right ahead. But you’ll discover the “theory” to figuring out how much width is added by the top of the sleeve requires you to applytrigonometry. Take it from someone who coded trig functions into several of her pattern generators, don’t do the trig just to check the sleeve length.. Design foldback cuffs and use the ribbing trick I suggested earlier. What with the gauge uncertainty and measurement errors, and rounding up or down to even numbers of rows and stitches, a 1/4″ isn’t going to matter!

But, as long as you don’t start obsessing over 1/4″, you should now know how to make sure sweaters you knit don’t have sleeves that end at the wearer’s knees!

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End notes:
1. By the way, I show how to measure all sorts of body parts here: How to measure.
2. Ok. I’m never off 5% on gauge. I knit swatches, but that’s not why I’m not off. It’s because I practice “adaptive knitting”. Some day I’ll explain that, and tell you how you can do it too! If you don’t use pattern generators or knit software, adaptive knitting involve calculations. But, you can avoid that if you use pattern generators!