Patterns that have a Bodice Front with darts, such as Cecily Dress by Sewgirl, are for a bust size B. As with most patterns of this type, they are designed for a 20 year old with a B-cup size bust. Obviously as we get older, our bodies change, so the pattern dart size and position are intended as a guide which can be altered easily to suit your size and shape.

So, for example, you may need to move the dart position up or down (Step 1), or increase or decrease the bust size to say a bra cup size C or D (Step 2). This blog post, shows you how to alter both the position of the dart and alter the cup size.

First of all you will need to find your Apex* point and mark it on your pattern.

So what exactly is the Apex*? Well, it is the middle of the fullest point of the bust (aka nipple!). To find this, (wearing your normal bra) just measure across from one apex to the other, so with me for example its 18cm that means its 9cm each side of the centre line. Then you need to measure how far down it is situated, so measure from the top shoulder to your Apex* (it usually helps to wear something with a shoulder seam and measure from there). Mine measures 33cm, so I mark on my pattern an X – 33cm down and 9cm away from the centre line of the bodice front. Now a quick way to check its correct, is to place the pattern up against you, and see where your apex* is situated. If it matches with the one you’ve marked then you are all good to go to the next stage i.e to move the dart position or do a bust size alteration (or both).


To tell whether your dart is too high or low, you need to see if the line that runs right through the middle of the dart hits the apex point. You can see from this diagram that it is too high, so it will need to be lowered.

bust 1

It needs to line up as shown in the diagram below…..the angle is not important.Screen Shot 2020-11-16 at 16.34.42To move a dart position up or down you can do by one of two methods:

  1. Slight Adjustment – if you just need just a slight adjustment, you can do this by changing the angle of the dart. So, firstly outline your size dart   triangle in red pen, so that you can see it really clearly. Then change the angle and redraw the dart so that it points towards the new apex point. NB. The dart tip needs to be at least 2.5cm (1 “) away from the apex.bust copy

2. Larger Adjustment To adjust the dart position more than a centimetre or so, you will need to use a cut and paste method. So, as in the previous method, outline your dart in red pen so that you can see it more clearly.

To maintain the angle of the dart, draw a box around the dart and cut out the box. Move it to the required position, then secure with sticky tape. Fill in the cut out section with paper and tape. NB make sure you keep your box straight and not slanted when you move it. bust copy



Measuring for your bra cup size- you will need to take two measurements of your bust – High Bust and Full Bust. Then subtract the high bust measurement from the full bust measurement (see the diagram A).


If you are:

less than 2.5cm /1″ then you are bra cup size AA

2.5cm /1″ then you are bra cup size A

5cm /2″ then you are bra cup size B

7.5cm / 3″ then you are bra cup size C

10cm / 4″ then you are bra cup size D

12.5cm / 5″ then you are bra cup size DD

15cm / 6″ then you are bra cup size DDD or UK size E

18cm / 7″ then you are bra cup size DDDD or UK size F

20.5cm / 8″ then you are bra cup size G/H or UK size FF

23cm / 9″ then you are bra cup size I or UK size G

25.5cm / 10″ then you are bra cup size J or UK size GG

The pattern is normally drafted to a size B, so you will need to reduce/increase each dart by the following measurements:

AA cup= reduce by 1cm on the

A cup= reduce by 1.25mm/ 1/2″

B cup = NO CHANGE  

C cup= add  1.25cm / 1/2″

D cup = add 2.5cm/ 1″

DD cup= add 3.75cm/ 1 1/2″

DDD cup (UK E) = add 5cm / 2″

DDDD cup (UK F) = add 6.25cm / 2 1/2″

G/H cup (UK FF) = add 7.5cm / 3″

I cup (UK G) = add 8.75cm / 3 1/2″

J cup (UK GG) = add 10cm / 4″


1. Firstly, draw three lines as shown by the red in the picture A, B and C (below)

Line A: extends from the Apex point* vertically to the lower edge.

Line B: extends from the Apex point to a point a third of the way up on the lower armhole.

Line C: extends from the Apex point to the side seam through the middle of the leg of the dart.Dart 1

2. Cut the lines as follows:

Line A: cut from the apex to the lower edge.

Line B: cut from the apex to the armhole edge but stop a few millimetres before the edge.

Line C: cut from the side seam to the apex but stop a few millimetres before the apex. dart 2

3. Spread the pieces apart adding on extra, according to your cup size shown above in the size guide. NB. Keep the pattern pieces together at the lower side, you don’t want to add on extra width at the bottom edge.

dart 4Cut a line across perpendicular to the line A, move so the pattern is aligned at the lower edge. Place a piece of paper behind each open section and tape in position. dart 5

This is now an increased bust dart. You will need to adjust the side line to match your lower pattern piece if necessary.


For cup sizes AA and A, you will need to reduce the size of the dart according to the measurements in the Size guide above. Instead of opening out the sections A, B and C you will need to close them, overlapping the pattern as shown below.

dart 2 A
dart 2 B
dart 2 C

The dart is adjusted in exactly the same way as increasing the dart but in reverse. Secure the overlap sections with sticky tape.

So, with a bit of know how, you can see its easy to make adjustments to your pattern. It pays to spend a little time prior to making your garment to get the fit just right. After adjusting your pattern, why not make a test garment out of cheaper fabric, or make up just a section of the garment beforehand such as just the Bodice Front and Back, It will allow you to relax in the knowledge that, being tried and tested, your project fit will fit correctly and will be a joy to wear. And, of course, after you have made your pattern adjustments, you can use the pattern piece again and again.

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