Saturday, November 9, 2019

How to Measure and True Seams, Tutorial.

Normally I post about a make and then I add whatever relevant tutorial or technical info to go with it in the post. This will be more of a technical post. Normally I would do those on my Instagram account (under the hashtag #miessewingtips ) but I think it will be too condensed in that format. So let's try this, and see how that goes.

I'm going to try to cover both very basic knowledge, but also a few more steps from that. And I've noticed that just because you are an experienced sewist, it doesn't necessarily mean that you have pattern knowledge, besides how to sew from them. So hopefully this will be helpful for a big group of people.

Since I'm a visual learner myself, I've tried to add photo or graphic examples of most of what I'm talking about. They are from different patterns and are sort of randomly chosen, since this is a general pattern info post.
In the end I do show how to remove the pointy hems of the Dale Knit Top from StyleArc and true the hem because I just posted that pattern on Instagram. See that post HERE for general pattern info.

Originally this post was about trueing seams. But I realized I needed to talk about measuring seams too because they are very close connected.

In short trueing seams means to make sure the seams make nice smooth lines when they are sewn together. 

This is of course essential to know when drafting patterns. But it's also good to know when making little (or big) pattern alterations to fit our individual bodies, or make design changes.

And there are lines everywhere in our clothes. A hem is one example of a line that we want to be smooth. Often we want it to be evenly (skirt same length) looking. Or if it's a hi(gh)-lo(w) hem, we want the hem to gradually dip down at the back, and not make a weird hard-dipping angle at the side seam, where the front and back pieces meet. Or remember when I talked about adding a bit of width to a pattern, and how the hem could become pointy?See it HERE if you missed it. But a pointy hem is a badly trued hem (unless it's a design feature of course but it generally pretty easy to see the difference, ha. 
But basically anywhere where we sew seams together, some kind of line will happen. Sew a shoulder seam together and now you have a neckline in one end and an armscye in the other end, and they should have smooth lines too (in general, of course there are design exceptions!).

Now that we know what it is, let's talk about how to do it.
Because I'm educated within the industrial sewing field, I'm used to drafting and working with patterns, that already have seam allowance (SA from now on) added. So that's what I'm going to base this tutorial on.

But first I just want to talk about how to measure whether your seams match up, because that's not the same thing as to check if a seam is trued.
To check whether seams match up, means to check that they are the same length.

And to show you how to do that, we need to talk about sewing lines vs outer lines/edges. Sewing lines is where we sew, and the outer lines/edges are the outer lines of the paper pattern or fabric after SA has been added. 

(Sorry, I borrowed this photos from my Dale Knit Top trueing tutorial which will come further down. In case you wonder why this is cut out so weird, ha.)
ALWAYS measure your seams in the sewing lines

Now if your pattern piece was a rectangle or square, it wouldn't make a difference where you measured. The seam is the same length whether you measure the outer line or you measure the sewing line 1 cm in (assuming SA is 1 cm). 
But as soon as we throw some curves or slanted lines in the picture, (and let's face it, our bodies are not square and neither are the pattern pieces usually for our clothes) then it does make a difference which line you measure. 
Imagine a circle (or look above, ha), and add another circle inside the first circle 1 cm from the original circle. Are they going to have the same circumference? Absolutely not. It's very simple math. 
And the same with curved seams such as hems, waistlines, sleeve caps, armscyes, necklines etc etc. The outer line and the sewing line is not going to have the same measurement in curved seams. The more curved, the bigger the difference. 
It's your sewing lines that represent your final garment, not the outer lines. Therefor, it's your sewing lines that has been drafted to match up (hopefully, ahem!) and they are the ones you have to focus on and measure.

You can measure seams several ways and it's good to know them all, because not all methods are equally suited for all type of seams.

The easy way is to put the two pattern pieces, that has the seams you want to compare/measure/check that they have the same length, on top of each other. You of course start by aligning the seam at the top or bottom, so we have a starting point. But remember it's the sewing line you need to check, NOT the outer line. 
So you need to align the start of the sewing lines on both pattern pieces/seams, which in the above photo, is where my pencil is pointing. This pattern has 1 cm SA as you can see, so we align them at the top, where they meet 1 cm in on the pattern. This might sound tricky when reading it, but I think it makes sense looking at it.

But this method can't always be done. 

Look at these seams. It's from a skirt with a twisting side seam but there is also some shape build in in the seam instead of sewing darts. These two seams can't be put on top of each other to be compared (at least not with a precise result) because the curves are not the same.

In this case you need your measuring tape.

Simply put your measuring tape sideways and measure....the sewing lines! Sorry, it looks a bit wonky up there. Normally I use both my hands, but I needed one hand to take the photo. 

Now there is a third way and that is also the way to use when trueing seams, so now we are finally getting to the subject I originally wanted to talk about, yay. 
 Why do I even talk so much about measuring seams, when I really wanted to talk about trueing seams? Because before you start trueing a seam, you'll have to make sure the two seams are the same length.
Now in some instances (shorter and fairly straight seams) you can do a length and trueing check in one go. But often you have to check length first and then true afterwards.


The third way, plus the method for trueing, is by overlapping the seams, so the sewing lines meet. And when I say overlapping I don't mean like the first method. I mean you put the pattern pieces with the seams that are going to be checked and/or trued, next to each other and then you push them towards each other until the sewing lines meet and the two SAs are overlapped. Phew, I'm so glad we have photos, see below.

Now if your sewing pattern has thin see-through paper and/or the sewing lines are actually drawn on the paper pieces, well then it's easy to do by simply using your eyes. You place the sewing lines on top of each other.
But not all sewing patterns with SA added, has the sewing lines marked. I was taught to just mark the corners of all the sewing lines when drafting patterns, some do it with notches and others again does no marking at all. Then what to do? Nope, not eyeball it, lol.

One way is of course to draw the sewing lines yourself. Find the SA and draw it on. Totally fine. 
But there's also another way, and that's what I'm showing you in the photos below. 

By the way the pattern in the photos is a pdf pattern and then it has my personal size and design alterations done too. So there is both printed cut out paper and my own pattern paper taped to it too. I think this also clearly shows why see-through tape that you can draw on, aka Scotch Magic Tape (not sponsored) is my preferred tape. THIS post will explain more, if you missed it.

It's a 'rule'/way I learned while I was a sewing trainee. It didn't totally made sense to me back then, as in I didn't fully understand it. So in the beginning, I just remembered the rule. I knew what I did was right, I just didn't understand why. Later it clicked and now I can't understand, why I couldn't understand, ha. So what I'm trying to say is, it's okay if you don't understand WHY right away. It might come later.

So the 'rule' is that you overlap the pattern pieces with the double amount of the SA. 
So if the seams on the pattern pieces, that you are going to check, has 1 cm SA, then you overlap the pattern pieces 2 cm. 

Photo 1)
I start by simply drawing a 2 cm line in on one of the pattern pieces...

 ...and then overlap the other piece to that line. Note it's here the outer line that meet that line I just drew 2 cm in.

That way the sewing lines will end up meeting on top of each other.

Photo 4) and 5)
You are seeing the same thing, just from afar and closer. And what you see is a seam that is not quite the same length and needs trueing (in this case simply because of the length discrepancy).
What you can't see on these photos, is me having put my heavy tape dispenser on top of the seams further up to keep them in place. Every little movement away from this 2 cm overlap will make the hem seam look different. If you still think they move too much, you can buy tape that is meant to be removed again. We used that in pattern classes from time to time but I live without it at the moment. But that will temporary keep them in place, while you draw your new line (hem in this case).

Photo 6)
Use your French curved ruler to remove the extra length plus TRUE the seam by making sure the new line is continuously smooth. 
You could also have decided to add to the pattern piece that was missing a bit of length, instead of removing the extra on the too long one. And just to be clear, this discrepancy of course happened because I altered the pattern and added width, not because there's a mistake in the original pattern! But removing the extra length was totally the fastest move, and no one will think...that skirt should have been 2 mm longer in the front, lol. As long as the lines are smooth, then tiny length differences will not be noticed in the final result. But always use your common sense.

Photo 7)
Finished result. As you can see I didn't touch the center front seam to the left. It's still a 90 degrees angle to the CF seam, like it should be to make sure the front seam is straight when cut to fold (and unfolded). In fact I didn't change that one pattern piece at all in this case. Other times when trueing, you'll need to add a bit to one and remove from the other. Or remove or add to both. Whatever it takes to make a smooth line.


Now how do you true a seam that is curved? Let me show you.

Photo 1) and 2)
So let's go back to the top of that seam where the curves of the seams are different. We want to check the line (red dots) that appears when the top of the side seam is sewn together. That's the waistline of this skirt.

Photo 3)
You still overlap the seams like before so the sewing lines meet. The SA is 1 cm, so you overlap the pattern pieces 2 cm.

Photo 4)
But as you can see here on this last photo, the seam is only overlapped at the top 10-15 cm (4-6") and that gives a good enough picture of a beautifully smooth curve at the top. No further trueing needed here.


Lastly I took some photos when I worked on the Dale Knit Top by StyleArc.

Originally I thought I both wanted to remove the pointy hem detail (design detail in this case, ha) and straighten out the whole front seam, as you can see at the photo to the right.

The photo to the left shows how the side seams are overlapped, and since it's a curved seam, you just overlap the lower 10-15 cm. You can see them not being overlapped further up.

And I just had to post a zoomed in version of the photo to the left above, where you can see where and how the sewing lines of the front and back lower side seams meet. As long as those points are meeting, then you can make changes to the hem. Again, this has an angled hem which is part of a design feature. If this was a regular hem, I would say this was a badly trued seam, ha.

Here you see how I use my French curved ruler to make a nice smooth nice to connect the front and back bodice/side seam.

The photo to the left shows the finished result with the front seam straightened out too. And the right photo shows how I decided to keep the diagonal seam. I simply folded that diagonal seam before cutting the fabric, so if I decide to make another Dale Knit Top with the fully straight front seam, I can simply unfold it.

I'm sorry I don't have a better shot of this, the tie band is covering some of the front, but I think you can see the diagonal front seam to the right. 

And here is a look at the now trued hem at the side seam. It might look a bit wavy but with the nature of this ribbed fabric, this is a result of that.

OKAY, I think I'm going to stop now. As always with these type of posts, I struggle with the balance of information. Do I give too much, too little? I honestly don't know. I just hope this will give at least a few AHA! moments.

Thank you!


  1. This is so helpful. Thank you!

  2. Thank you so much. I've just discovered your blog and this is all the information I've needed to get my head around the way I want to sew. I took Trade and Couture RSA back in the 70s but never used it except for myself and family in the end. I'm often conflicted between trade and couture processes and see so much out there for beginners, but so little for those coming back to sewing who know a bit but have forgotten most of it! This is what I need to true a pattern I took from a top I love but didn't get the alignment right. I've got so much catch up reading to do! I love the way you write, it's every engaging so I think you've got the balance just right. Thank you again!

    1. Barbara thank you so much for your comment. I agree with you, that there is much more sewing info for beginners out there than for the more experienced. That's why I thought I would focus more on that and let other people do the beginner stuff. I'm glad you found my blog and yes, after 8 years of blogging, you certainly have some catching up to do, ha. Thank you for reading and enjoy your comeback to sewing.

    2. Thank you so much for this. There is a lot of stuff for beginners out there, as you say... I learnt some things by osmosis, I think, because I remember using a pattern by By Hand London with a panelled skirt and thinking that it couldn't be right because each panel ended on a straight hem with no little raised edges. It was a famous dress (Anna) that everyone loved, but the front and back bodice were both the same length and it just didn't work for me. Luckily I didn't bother cutting out all the panels. I was quite experienced at the time but oh, how I wish I had your blog to look at back then! Luckily I have found it because I have learnt so many new things rom this post and others of yours. All a long winded way of saying thank you so much for taking the time to post all this wonderful information, and going into the perfect amount of detail.

  3. Thanks for the information! I found it clear to follow along and the pictures were very helpful.


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Thank you!