# Tutorial 3. Calculating Pattern Alterations. Part 1.

## Tutorial 3. Calculating Pattern Alterations. Part 1.

Let us start doing calculations for our pattern.

I have drawn a table on my writing board and filled out all relevant columns.

Let me list the measurements I'm going to use (column 1):

- Bust front,

- Under-bust front,

- Bust circumference,

- Under-bust circumference,

- Waist circumference,

- Stomach circumference 13cm below the waistline,

- Hip circumference 22cm below the waistline. It's very important to know where exactly you took these measurements. It becomes particularly urgent when you're sewing a slim-fit dress (for example, a mermaid dress), because the side contour of the client's body is crucial then. Therefore you need to know precisely at what distance from the waistline you're taking the hip circumference measurement.

- Bust middle,

- Clip,

- Back width,

- Between the shoulder straps at the back,

- Height of the corner for attaching shoulder straps,

The last three measurements – back width, between the shoulder straps and corner height – are only taken in case you want to add corners for attaching shoulder straps at the back.

- Armscye circumference. This measurement is required in order to pre-cut a shoulder strap, secure it on the dress and adjust its proper length during a fitting.

Let’s begin calculating.

I will give you detailed explanations. There is a lot to discuss because we are dealing with a non-standard figure with full breasts, a thin waist, and moderate hips. This woman has a beautiful silhouette but, as you will see, it requires a lot greater values to adjust the pattern along the bust line than along the hip line. Her waist circumference coincides with that on the pattern. Such body proportions are quite common and people often ask me how to calculate and build a pattern for a similar figure.

You always start calculating from the first top lines of the table looking to the bust front and under-bust front measurements. This allows you to determine the location of the side seam.

But there's something unexpected waiting right ahead.

Bust front measurement: 56cm on the client and 49cm on the pattern.

56cm – 49cm = -7cm

I divide it in half because there are two side seams. Now it's obvious that I need to expand the pattern by 3.5cm from each side.

Under-bust front measurement: 41cm on the client and 40cm on the pattern.

41cm – 40cm = -1cm

I divide it in half to account for two side seams. It turns out I need to expand the pattern by only 0.5cm from each side.

My students usually get puzzled here. What to do? What adjustment value to choose to expand the pattern now? Where to take guidance from?

The second thing you need to pay attention to is the clip measurement.

It’s not all that simple in our case. The thing is we are going to use a different pattern for each side of the dress:  a strapless pattern and a pattern with a corner for attaching shoulder straps at the back.

These patterns have unlike clip measurements. I have written one above the other (column 3).

Clip measurement on the strapless pattern:  11.5cm towards the armscye or the underarm; 10cm from the apex of the bust to the top edge of the corset; and 9cm from the bust line to the top of the corset.

Clip measurement on the side of the front that will feature a corner:   12.5cm towards the armscye; and the height of the corner is 11cm.

My client's clip measurement:  14cm to the underarm; 14cm from the bust line to the neckline, and the height of the corner is 14cm as well.

What value should I take?

If you use the strapless pattern as a guide, then you need to add the following value to the clip measurement:

14cm – 11.5cm = 2.5cm

If you use the corner pattern as a guide, then you need to add the following value to the clip measurement:

14cm – 12.5cm = 1.5cm

The clip measurements are pointing at the adjustment values of 2.5cm and 1.5cm while the bust front and under-bust front measurements are pointing at 3.5cm and 0.5cm.

At the first glance you have no idea how to calculate pattern adjustments in this case. All values are absolutely different! But don't be distressed, it is not a big deal!

You should be able to imagine in what way you are going to alter the pattern after looking at the clip and the side seam configuration.

Suppose you shift the side seam outwards by 3.5cm. And you need to shift it by 1.5cm or 2.5cm in the underarm area. Shifting the side seam outwards by 3.5cm will result in shifting it by about 3cm in the underarm area. In other words, 3.5cm is a slightly too large adjustment value.

But if you shift the side seam by 3cm, it will get shifted by 2-2.5cm in the underarm area. And that's exactly what you want! It's how you achieve necessary adjustment values for the clip measurement.

Let's write 3cm in the table (column 4, lines 3-7).

You could also write 2.5cm, it wouldn't be bad either. But I felt like taking 3cm to make a round value. It's my own subjective opinion, feel free to take 2.5cm if you prefer. I just thought it would be better to adopt an adjustment value that's closer to our calculations to avoid shifting the side seam way too far towards the front.  It's why I have opted for 3cm.

Please note that the next column of our table is titled Side Front Adjusted. We might re-calculate things later.

There are no alterations in the bust middle measurements. I write a zero in the table.

Clip measurements:

For the strapless pattern (top line):  I write 2.5cm, 4cm and 1cm in the table.

For the pattern with a corner (bottom line):  I write 1.5cm and 3cm in the table.

We won't look at the measurements of the back and the shoulder straps just yet.

Let's leave the table as it is at this stage.

And now we need to calculate the side seam configuration at the back (column 6). We leave the adjusted side seam of the front untouched for now.

Let’s begin calculating. You’ll see what happens after I take into account all measurements and calculations from the table.

The bust front and the under-bust front measurements are not involved in these calculations. I write dashes in the table (column 6).

Bust circumference: It is 102cm on the client and 93cm on the pattern.

However I have already expanded the pattern by 3cm from each side – a total of 6cm.

93cm+ 6cm= 99cm

102cm – 99cm = 3cm

I divide it in half. As a result, I need to expand the back by 1.5cm from each side. I write 1.5cm in the table.

Under-bust circumference, It is 82cm on the client and 80cm on the pattern.

However I have already expanded the pattern by 3cm from each side – a total of 6cm.

80cm+ 6cm= 86cm

82cm– 86cm = -4cm

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

Waist circumference: It is 75cm on the client and 75cm on the pattern.

However I have already expanded the pattern by 3cm from each side – a total of 6cm.

75cm+ 6cm= 81cm

75cm – 81cm = -6cm

I divide it in half. As a result, I need to narrow the back down by 3cm from each side. I write -3cm in the table.

Stomach circumference: It is 103cm on the client and 95cm on the pattern.

However I have already expanded the pattern by 3cm from each side – a total of 6cm.

95cm+ 6cm= 101cm

103cm – 101cm = 2cm

I divide it in half. As a result, I need to expand the back by 1cm from each side. I write 1cm in the table.

Hip circumference: it’s 110cm on the client and 103cm on the pattern.

However I have already expanded the pattern by 3cm from each side – a total of 6cm.

103cm+ 6cm= 109cm

110cm – 109cm = 1cm.

I divide it in half. As a result, I need to expand the back by 0.5cm from each side along the stomach line. I write 0.5cm in the table.

Bust middle and clip measurements are not involved in these calculations. I write dashes in the table (column 6).

Now that we have reached this stage of calculations, let me explain in more detail what 'back width' and 'between shoulder straps back' actually means. I will demonstrate it on the pattern so you can see how to construct those shoulder strap corners at the back of the corset. It's a very frequently asked question. Although I have already explained it many times on various DVD's, it seems like some of you have somehow missed out on this know-how.

I take the central and the side piece of the back.

The central piece has a 2cm seam allowance for the central seam of the back and a 1.2cm seam allowance for the princess seam.

I take a ruler, measure the distance from edge to edge in a straight line, and then subtract the seam allowances of 2cm and 1.2cm.

What I get is a section that is 9.5cm long.

Now imagine the finished garment. There will be a mirrored half of the dress on the left, i.e. another central piece and another side piece.

If there is 9.5cm from the centre of the back to the princess seam on the first central piece, then it will be the same on the other symmetric central piece. Therefore, it will make a total of 19cm without the seam allowances when the client puts the dress on and zips it up.

There is 19cm between the princess seams at the back.

I have also taken the back width measurement off my client – 38cm. But this 38cm is the entire width of the back that includes both central and both side pieces.

Let us determine the distance from the princess seam of the side piece to the end point of the back width measurement (or the client's arm).

(38cm- 19cm) ÷ 2 = 9.5cm

We need to mark this 9.5cm from the princess seam of the side piece. That is the exact spot from which we measure the width of the back: the area that we want to cover up.  In other words, this is where the back will have a rise. I record the value into the table.

Of course, you could also mark 9.5cm and add the seam allowance. It's even more precise. So from the edge of the seam allowance you mark:

9.5cm + 1.2cm = 10.7cm, and this is the place of the rise with the seam allowance included.

Now we need to find the correct way to place the corner for the shoulder strap. For this very reason we measured the distance between the straps. It is 26cm in my client's case.

We do all the same things.  There is 26cm between the shoulder straps and 19 cm between the princess seams of the back (its raw edges put together).

(26cm- 19cm) ÷ 2 = 3.5cm

I record that value into the table.

You can mark 3.5cm from the seam allowance horizontally and mark the height of the corner (26cm) with a perpendicular line going upwards from the waist.

That's the top point of the corner. You find the point where the line beings to arch and connect it with the top of the corner.  Draw a smooth line down to the middle of the back in the other direction.

I will draw it all on the writing board after we do our calculations. I will return to this issue to make sure everyone gets the hang of it. I know it always raises many questions.

Our table looks like this at the moment:

Let us look at our "pretty" side seam of the back. It's a total mess – there's a wide scatter of adjustment values. What do we do about it? We simply need to analyze all these values.

There are two measurements with the greatest difference between their adjustment values: under-bust circumference and waistline circumference. These are the areas that were closest to the pattern and

Well, let us adjust the configuration of the side seam of the back then. There is actually nothing wrong if we take the liberty of deviating from the line drawn on the pattern. The client has a non-standard figure with ample breasts. We need to find a way out.

The side seam of the front and the side seam of the back have an identical configuration on the pattern. We have expanded the front by 3cm along the entire side seam.

So we have shifted it 3cm outwards at the bust line. What if we shift it outwards by 2cm and not 3cm below the bust? We will then also shift it 3cm outwards in the waistline and then return to the adjustment value of 3cm in the stomach and in the hips.

It will be a rather nicely shaped side seam but let us remember that it features a non-standard transition with a difference of 1cm.

It means we will need to make an identical transition on the side seam of the back.

I write the adjustment values of the side seam of the front into the table (column 5). We will make it 3cm at the bust line, 2cm at the under-bust line, 2cm in the waist, 3cm in the stomach and 3cm in the hips.

Now let us re-define the side seam contour of the back. Column 7.

Looking at all this "beauty" makes me think, "She has a full bust so we can by no means change it along the bust line. The adjustment value will stay as big as it is now." Let us agree upon 1.5cm.

We need to make the adjustment value 1cm smaller along the under-bust line to keep identical side seam configurations at the front and at the back. It should be 0.5cm then.

The incline of the side seam does not change in the waist so we leave it at 0.5cm.

The adjustment value in the stomach and in the hips should be the same as along the bust line (1.5cm) to preserve the incline of the side seam.

So we have made up our mind about the adjustment values for the side seams of the front and back.

Since there are extra centimeters left, we will take advantage of the princess seams of the front and back. These are columns 8 and 9 correspondingly.