# Tutorial 1. Calculating Pattern Alterations.

Let me start calculating adjustments to the standard pattern. I draw a table with eight columns.

I will use the same measurements I always use for sewing corsets. You don't need any additional measurements in this case.

What you need to know are:

- Bust front,

- Under-bust front,

- Bust circumference,

- Under-bust circumference,

- Waist circumference,

- Stomach circumference. Make sure to record the distance from the waist in brackets. In this case, I measured the stomach circumference 9cm and not 12cm below the waistline. I did so because with this new pattern it is desirable to take this measurement somewhere between the waistline and the hip line. It will help me adjust the configuration of the side seam, the front, and the back of the dress. Since the distance from the waistline to the hip line is about 19cm, I took the stomach circumference 9cm below the waistline.

- Hip circumference. And again, I mark the distance from the waist in brackets. I took this measurement 19cm below the waist.

- Bust middle,

- Clip 1 (toward the armscye) and clip 2 (toward the corner),

- Front neck depth (measured up from the bust line),

- Side length,

- Blade height back. Let me remind you that the blade height back measurement determines how tall the back of the finished garment should be. If the back of the dress surpasses your client's bottom shoulder blade line, the dress will likely be too tight and, as the result, there will be skin bulging over the back neckline.

These are all measurements required for customizing the standard dress pattern.

I have taken measurements off my client and written them in the table (column 1).

The pattern measurements from column 2 were taken off the mock-up sewn after the pattern.

I highly recommend you should sew your own mock-up after the standard pattern before calculating adjustments. By doing so, you will see how to align and join all pieces. Simply sew a mock-up from plain cotton fabric, put it on the dress-form, and stuff all hollows with padding polyester, wadding, or bits of fabric. Then tie cords around the major circumference lines. You can use the notches on the pattern as guidelines or position the cords the way you find appropriate. And then you take all measurements off the mock-up the same way you would take them off your client.

I have recorded these measurements in column 2. Don’t worry if your values differ from mine: they are your own measurements in the end. Just make sure you take them off your client exactly the same way.

I start by analyzing the three foundational measurements.

Bust middle:

This measurement will show if we need to adjust the central front piece. I can tell that the client's bust middle measurement coincides with that of the pattern, which means there is no need in adding a column for calculations related to the central front piece. If these measurements were different, I would have drawn an additional Bust Middle column and accounted for the difference in all subsequent calculations. Please remember that the bust middle measurement is not taken the same way in corset garments as in casual garments. This measurement indicates the position of the front princess seams on the ready garment and depends on your client's figure. You need to look at her and decide it together where to place these front princess seams. The distance between the front princess seams at the level of the bust line will be your bust middle measurement.

Bust front and under-bust front.

These measurements indicate the configuration of the side seam line on the pattern customized after client's measurements.

Let us determine the configuration of the front side seam line.  All calculated values are written in column 3.

Bust front measurement is 46cm on the client and 48cm on the pattern.

46cm – 48cm = -2cm

The pattern is 2cm larger than needed. I divide the value in half because there are two side seams. As the result, I need to remove 1cm from either side of the pattern.

Under-bust front is 40cm on the client and 38cm on the pattern.

40cm – 38cm = 2cm

This time the pattern is 2cm smaller than it should be. I divide the value in half. As the result, I need to widen the pattern by 1cm from either side.

As you can see, I got two absolutely opposite results for the first two measurements: -1cm and +1cm.

I will know how to change the front side seam line of the standard pattern after analyzing the rest of the measurements. Most measurements of the standard pattern are larger than the ones taken off the client. The only exception is the under-bust circumference (the measurements coincide). It makes sense, in this case, to shift the entire side seam line of the standard pattern inwards by a fixed value: for example, 1cm. I write the pre-estimated adjustment value of -1cm into column 3. I will define precise adjustments to the front side seam line in further calculations.

And now let us continue calculating adjustments to the configuration of the front side seam line.

Bust middle.

The measurements coincide and I write a zero in the table.

Clips 1 and 2.

In this case, this measurement is taken from the bust apex point to the armscye (clip 1) and from the bust apex point up along the princess seam (clip 2). The second clip measurement roughly determines the length of the cup.

- Clip 1 measurements coincide and I write a zero in the table.

- Clip 2 is 6cm on the client and 8.5cm on the pattern.

6cm – 8.5cm = -2.5cm

The cup is 2.5cm taller than needed. I write -2.5cm in the table.

Front neck depth (taken from the bust line) is 5cm on the client and 7.5cm on the pattern.

5cm – 7.5cm = -2.5cm

The front neck depth is 2.5cm larger than needed. I write -2.5cm in the table.

Side length is 19cm on the client and 20cm on the pattern.

19cm – 20cm = -1cm

The side length measurement is 1cm bigger than needed. I write the pre-estimated value of -1cm in the table. I will double check it when building the pattern.

Blade height back is 20cm on the client and 18cm on the pattern.

20cm – 18cm = 2cm

Since the blade height back measurement is 2cm smaller on the pattern than on the client, there is no risk of skin bulging over the back neckline. No changes needed. I write dashes in the table.

I will calculate the final adjustments to the front side seam line after calculating all adjustments to the back side seam line.

I move on to the back side seam line. First I will calculate pre-estimated adjustment values and write them in column 5.

The bust front and under-bust front measurements are not involved in these calculations. I write dashes in the table.

Bust circumference is 86cm on the client and 92cm on the pattern.

But I have already adjusted the pattern down by 1cm from either side, i.e. a total of 2cm.

92cm - 2cm = 90cm

86cm – 90cm = -4cm

I divide the value in half. As a result, I need to narrow the back by 2cm from either side. I write -2cm in the table.

Under-bust circumference is 78cm on the client and 78cm on the pattern.

But I have already adjusted the pattern down by 1cm from either side, i.e. a total of 2cm.

78cm- 2cm= 76cm

78cm – 76cm = 2cm

Again, I divide it in half. As the result, I need to widen the pattern by 1cm from either side. I write 1cm in the table.

Waist circumference is 68cm on the client and 72cm on the pattern.

But I have already adjusted the pattern down by 1cm from either side, i.e. a total of 2cm.

72cm- 2cm= 70cm

68cm – 70cm = -2cm

I divide it in half. As the result, I need to remove 1cm from either side of the pattern. I write -1cm in the table.

Stomach circumference is 80cm on the client and it is 88cm on the pattern.

I have already adjusted the pattern down by 1cm from either side, i.e. a total of 2cm. Therefore:

88cm- 2cm= 86cm

80cm – 86cm = -6cm

I divide the value in half. As the result, I need to remove 3cm from either side of the pattern. I write -3cm in the table.

Hip circumference is 98cm on the client and 100cm on the pattern.

But I have already adjusted the pattern down by 1cm from either side, i.e. a total of 2cm.

100cm- 2cm= 98cm

98cm – 98cm = 0cm

It follows that the pattern meets my client's measurement in the hips. I write a zero in the table.

Bust middle, clip, front neck depth, and blade height back are not involved in the calculations of the back side seam line. I write dashes in the table.

The pre-estimated adjustment to the side length measurement stays the same. I write -1cm in the table.

Judging by the values in the Side Seam Back column, the back side seam line resembles a zigzag.

I have to apply alterations to the front and the back princess seams to even out the side seam line.

There is a significant difference though, between my new pattern and the classic corset pattern I used before, where front and back princess seams were straight and ran from the top all the way down to the bottom.

With the old pattern, I could adjust the front princess seams only in the waist, stomach, and hips, and the back princess seams – along their full length, i.e. in the bust, under the bust, in the waist, stomach, and hips.

The situation becomes somewhat different with the new pattern. The princess seams between the intermediate front pieces and the side front pieces allow for adjustments at the level of the under-bust line, the waistline, and the stomach line.

I cannot change anything at the hip line level though because it is exactly where the front princess seams acquire their semi-circle shape. It is where they meet the intermediate front princess seams.

I can't change anything at the hip line level because, if I do, I will have to change the configuration of the entire pattern and the shape of the princess seams.

The same thing happens with the back half of the dress. I can't apply any adjustments at the hip line level because it is where the back princess seams stop. Therefore, I can only apply adjustments to the back princess seams along the bust line, the under-bust line, the waistline, and the stomach line.

The main conclusion is neither front nor back princess seams must be changed at the hip line level! There are no adjustments to the back side seam line at the hip line level in this particular case. I have put a zero in the table.

But I do need to choose a fixed value for adjusting the entire back side seam line.

Let's return to the hip line. I have shifted the front side seam line 1cm inwards. This implies no adjustments to the back side seam line. Both side seam lines need to have the same incline though. Considering that the princess seams must stay unchanged at the hip line level, I have decided to split the adjustment to the front side seam line into two equal adjustments, i.e. shift both the front side seam line and the back side seam line 0.5cm inwards.

I write -0.5cm under Side Seam Front Adjusted and Side Seam Back Adjusted (columns 4 and 5).

It is not enough to shift the entire back side seam line 0.5cm inwards though because it requires a lot more considerable alterations according to the calculations. We should also remember that the side seam lines must have the same incline.

I have decided to adopt a fixed value of -1cm for adjusting both side seam lines (front and back).

The only exception is the hip line level where I leave it at -0.5cm.

In this case, both side seam lines will have the same configuration.

And now I need to apply the changes to the front and the back princess seams to adjust the size of the pattern with respect to my client's size.

I start from the bust line. During calculations, I must also remember to account for bust front and under- bust front adjustments to determine whether I need to apply changes to the intermediate princess seam lines at the front and the back of the dress or solely at the back.

Back to the bust line. It is 86cm on the client and 92cm on the pattern.

I have, however, already adjusted the pattern down by shifting the front side seam line 1cm inwards from either side, i.e. a total of 2cm (column 3, line 1), and by doing the same with the adjusted back side seam line (column 4, line 3).  In other words, I have adjusted the pattern down by 4cm.

92cm – 4cm = 188cm

86cm – 88cm = -2cm

As you can see, I need to adjust it down by another 2cm by applying changes to the princess seams at the front and at the back of the dress. I have already removed 1cm from the bust front measurement at the bust line level to even out the side seam lines of the front and the back half of the dress, so I will remove this excess 2cm using only the back princess seams, i.e. without touching the front princess seams .

There are two princess seams and therefore four raw edges at the back of the dress.

-2cm / 4 = -0.5cm

I need to shift the back princess seams 0.5cm inwards at the bust line level. I write 0 and -0.5 in the table (columns 7 and 8, line 3).

Let's move to the under-bust line. The under-bust front is 78cm on the client and 72cm on the pattern.

I should have shifted the front side seam line 1cm outwards from either side at the under-bust line level (column 3, line 2) to get it aligned with the back side seam line. And I have done just the opposite: shifted it 1cm inwards from either side (column 4, line 4). It means I need to shift the intermediate front princess seams outwards by a total of 2cm distributed between their four raw edges.

-2cm / 4 = -0.5cm

Now I need to calculate necessary adjustments to the back princess seams to bring the pattern measurement up to my client's measurement (78cm).

The standard pattern has been adjusted down: the front side seam line has been shifted 1cm inwards from either side (2cm total), and the same thing has been done to the back side seam line. I have added 2cm using the intermediate front princess seams though.

78cm– 2cm – 2cm + 2cm = 76cm

78cm – 76cm = 2cm

As you can see, I need to add 2cm to the standard pattern using the back princess seams.

-2cm / 4 = -0.5cm

I need to shift the front and the back princess seams 0.5cm outwards at the under-bust level. I write it in the table (columns 7 and 8, line 4).

Waistline. It is 68cm on the client and 72cm on the pattern.

The standard pattern has been adjusted down: the front side seam line has been shifted 1cm inwards from either side (2cm total), and the same thing has been done to the back side seam line. In other words, I have made it 4cm smaller.

72cm – 4cm = 68cm

68cm– 68cm= 0cm

I have already arrived at my client's measurement so I don't need to remove anything in the front or the back princess seams here. I put a zero in line 5 of columns 7 and 8.

Let's move to the stomach line. My client’s measurement is 80cm and it is 88cm on the pattern.

Again, the standard pattern has been adjusted down by a total of 4cm: the front side seam line has been shifted 1cm inwards from either side (2cm total), and the same thing has been done to the back side seam line.

88cm – 4cm = 84cm

80cm – 84cm = -4cm

As you can see, I need to remove another 4cm by applying changes to the princess seam lines at the front and at the back of the dress. If I want to do it using the intermediate front and back princess seams, then I am supposed to divide 4cm between the eight raw edges and shift each princess seam line 0.5cm inwards.

-4cm / 8 = -0.5cm

In this case though, the back princess seams will bend way too abruptly in the area between the waistline and the stomach line, which may result in a poor fit of the dress. I will use both the main and the intermediate princess seams on the front half of the dress alongside the back princess seams to solve this problem. This way I can distribute the total value of 4cm between 12 raw edges.

4cm / 12 = 0.3cm

This will reduce the bend of the back princess seam in the area between the waistline and the stomach line considerably.

I write -0.3cm in the table (column 7 and 8, line 6) and make a note to remember that I am supposed to shift both princess seams at the front.

I am not allowed to change the princess seams at the hip line level. I put a zero in line 7 of columns 7 and 8.

That's it! We are done with the calculations!

I highly recommend you double-check all calculated values before altering your paper pattern. Simply sum up all adjustment values along each circumference line and add the total to the pattern measurement. The result is supposed to equal your client's measurement.

Moreover, I recommend you print out two sets of patterns and apply adjustments to one of them. First sew a mock-up based on the standard pattern and then sew another mock-up based on the adjusted pattern, put it on the dress-form, and measure it. It will help you avoid many mistakes.

Every new pattern that lands in your hands requires that you try it out, true it, and polish it up. Do not start cutting fabric (especially, an expensive kind) unless you are absolutely confident in your pattern.

It is why I insist on sewing a mock-up after customizing the pattern.