Sewing Pattern Alteration


What is pattern alteration? Why would I do it?


One of the best reasons to make your own clothes is to create garments that are custom-fitted to your exact measurements and proportions.

Any sewing pattern can be altered to improve the fit, but the skills required to alter a pattern are only picked up through practicing and reading up on the methods involved. But the effort is totally worth it...I mean, who wouldn't want flattering, custom-fit clothes?


Obviously, when you buy clothes on the high street you buy a standard size of clothing e.g. size 10, 12 etc... but one size 10 woman’s shape can differ so much from another size 10 woman's shape.

They could have an athletic or hourglass figure; have a small or a large bust; be petite or tall in stature. You may be lucky and a standard size fits you perfectly, but it’s unlikely!


Photo by wck.


Unfortunately, this problem doesn’t disappear automatically when you start to make your own clothes, because sewing patterns are also provided in standard sizes. So that’s where pattern alteration comes in; to improve your clothes, you should alter the provided pattern to fit you.


This isn’t something beginners must know, so don’t feel overwhelmed if you’re just starting out. You can learn these skills little by little, over time. Just focus on making the standard sizes first, and slowly learn how your body shape differs to the standard.

For instance, you may start to notice that clothes you make are always a bit tight around your waist, or too baggy around the bust area. Make a mental note of these observations, because when you do start learning pattern alteration methods, you can focus first on fixing the sizing problems you encounter most commonly.


Examples of alteration techniques include slash and spread, slash and overlap, and pivoting. You must use specific methods to alter a pattern, because doing it as ‘guesswork’ or just doing it ‘by eye’ will get you in a pickle!

For making a piece of clothing longer, you may be able to alter the pattern successfully yourself without too much knowledge, but more complicated alterations like moving darts or reducing the bust size requires a set method. Accuracy is key in dressmaking, and if one measurement is changed on a pattern, then at least one other measurement will have to be changed too, to balance it out.


It’s so easy to get overwhelmed about dressmaking methods because it will seem complex at first, but honestly when you get into it and learn each process and why you are doing each step, it will become clear. I promise!


The First Steps


So how do you know that your clothing doesn't fit well? What are the particular warning signs?


Well, firstly, judge whether the item of clothing is comfortable to wear.

Next, you should look at whether there are any places where the fabric is sagging, wrinkling or straining.

Take a look at the garment overall and assess whether it's too large or too small in general, or only in specific places. If it's too large overall, you may just need to make the garment in a smaller size. But if only some areas are too large (or small), then those need to be tackled individually.


Learn to analyse your clothing and ask whether it flatters your body shape or not. And if it's unflattering, why do you think that is? Are the darts in the correct places? Is it too short or too long? Too tight in the wrong places?

It's also a great idea to understand what body shape you have (e.g. pear, apple etc.) and research what kinds of clothing styles suit your body shape before you start making clothes. That way, you don't pick unflattering clothes to make in the first place, as this could end up denting your confidence and pride in your work.


Public domain photo from Pixabay.


How to Start Altering Patterns


Looser clothing will no doubt need less pattern alteration than form-fitting clothing, so it's much easier to start by altering a pattern for a garment that isn't required to closely follow all of the curves of your body. Make it easier for yourself and pick a pattern that incorporates minimal darts and seams.

Try and choose a simple tunic or vest top, or a skirt, as your first pattern to try and alter. Something with as few details and embellishments as possible, because you just want to look at the fit and not get distracted by the details.


In fact, even before you look at patterns to alter, it would be a great idea to get an old baggy t-shirt and, whilst wearing the top, carefully use dressmaking pins to pinch the excess fabric together and try and make the t-shirt into a closer, more flattering fit.

Any alterations you make should be symmetrical, so if you add a dart on one side, add the same on the other side. Don't just pinch excess fabric together on one side or you'll end up with a very odd looking top!

This is just a useful exercise to understand your body better, and how fabric moves over it.


And now back to pattern altering :)


So now you've chosen a simple pattern, what do you do next?


Well, technically speaking there are three ways of altering fit; a) on the pattern itself (before you make the garment or even cut any fabric), b) by making a toile (a cheap 'practice' of the finished garment) and altering the fit of that first, or c) by altering the garment itself after you've made it (which is usually done on a dressform, and is only suitable for some minor alterations).


Of course, the first two options of making alterations before construction are the easier, more efficient and less wasteful methods, so we'll stick with those moving forward :)



The first step of sewing any pattern is, in my opinion, to copy the provided sewing pattern onto new pattern paper.

Some people don't do this, but I think keeping the original pattern intact is very important, especially if you're making alterations, because things can sometimes go awry and you'll want to be able to start again if you need to!


If you instead chose to work directly with the original pattern, then any changes you make will permanently alter that pattern...plus, sewing pattern paper is so delicate that it can be easier to work on slightly more sturdy paper instead. You can buy wide rolls of paper (bond paper, tracing paper, freezer paper...) for this very application, which is easier than taping smaller pieces of paper together.


So that's the first step; trace out the pattern and all the important lines (seamlines, darts etc.) onto new pattern paper.


The pattern lines you choose to follow will be based on your size e.g. if you're a size 10, you would follow the lines marked for a size 10.

However, before you start, be sure to take your own measurements accurately and use the sizing chart included with the sewing pattern to determine which size lines you must follow. Don't just assume you are using the same size you always wear.



The best thing to do next would be to make a toile (also called a muslin)

(i.e. option 'b' from above.)

This is a rough (unfinished) version of the final garment made from cheap fabric, and is the best way to get a good fit.

It's particularly a good idea for beginners to make a toile, because it's extra sewing practice (which is always valuable) and is like doing a 'test run' before making the 'real thing'. This should make you more confident when it comes to making the actual garment.



You could instead alter the pattern without cutting any fabric at all (option 'a' from above), which is a good choice if you are experienced enough with alteration methods already and you know what needs altering and how.

For instance, you could already know that the top half of a dress will need to be a size 8, but the bottom half needs to be a size 12 to fit you (a classic problem if you're a 'pear shape'.)

Or maybe you know you want the dress to be 1" longer. These sorts of alterations, which you know you are going to want to make, can be done straight onto the pattern.



There is also a method called tissue fitting that you can do prior to making a toile, or instead of. This involves pinning the sewing pattern together at the correct points, just as if you were pinning together pieces of fabric. This includes pinning along dart lines and any other pattern lines that you would nornally sew along.

Then you 'wear' this paper garment to see how it fits you.

A sewing pattern usually only provides enough templates to make half of the garment using the actual pattern paper - due to the fact that most garments are symmetrical and there's no point providing two templates for the same shaped piece.

Therefore, you will be tissue fitting with half of a paper garment and will need hold the paper onto your body to keep it in place.

As an example of alterations you can do with tissue fitting; once you're holding the half-garment in place on your body, you would check whether the centre line - i.e. the edge of the paper on the front of your body - does in fact line up with the centre of your body.

If it doesn't make it to the centre of your body, you will need to enlarge the pattern, and if it strays onto the other half of your body, you'll need to make the pattern less wide.

Tissue fitting is a quicker method than making a toile, however it is more fiddly and less accurate, and is also difficult to do alone.



Or, the other method option ('c' from above) is to make the final garment and then make any alterations you want.

I would only advise doing this if you are experienced in sewing and alteration, and you know that you will only want to be making small adjustments to the clothing.

Major alterations like making the bust size bigger are impossible to do on a finished item because it would require addition of fabric.


In conclusion, I would definitely recommend choosing option 'b' (making a toile) as the next step, although of course it's totally up to you.

You might be put off because it seems like lots of extra work and a waste of fabric to make a toile, but it is simply the most reliable method, and (to me, at least) the most straight forward.



So what do you do after making a toile?


This is the point where you follow certain techniques to make the alterations.


The easiest of alterations is to make a hem line shorter by marking (in a marker pen, onto the toile itself) how much excess fabric you would want removing.

If you want a hemline longer, you can add extra fabric to your toile with sewing pins first, and then a basting stitch (a long straight stitch) to fix your alteration in place.

Another fairly easy alteration is to make something smaller or narrower, and this is done by pinching the excess fabric together and fixing in place with sewing pins and then a basting stitch.

Another way to decrease dimensions is to overlap your pattern along pattern lines, such as seam lines.


To make an area bigger or wider, you 'slash and spread', which basically means cutting the fabric, opening up this cut line so it becomes the width you want, and then adding extra fabric into the gap.


If you make dimensional changes, it is likely that you will also need to reposition darts and seams, since any change you make to a pattern will have a knock-on effect on the rest of the garment.


But don't worry, I intend to go through all of these alteration techniques in the future, one at a time, and make the instructions as straightforward as possible for beginners.


As a last step, the alterations made to the toile would then be transferred onto the sewing pattern. Then the final garment can be made with the new templates.


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What is 'ease'?


I thought I'd put the definition of 'ease' here because it's useful to always have in your mind when altering patterns.

On this page I've talked a lot about clothes fitting your form, but what you don't want to do is make a garment that fits your body so well that you can't move in it!

That's what 'ease' prevents; ease is the in-built 'give' in a garment that means you can still move comfortably in the piece of clothing, so it doesn't restrict your movements by being too fitted to your body.


So when you are trying on your toile, make sure you move about in it too, including sitting down and putting your arms up in the air, to make sure you are getting a good fit as well as leaving in 'ease' to allow free movement.

For instance, if a top is designed for a 34" bust, the actual bust measurement might actually be 36" to allow 2" of 'ease'.

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