The Basics of a Chest Transformation

How do you know if a transformation is necessary?

Key point : all the instructions in this tutorial only apply in the case of a pattern transformation to the chest and are not valid for defining your size in lingerie.

The majority of bodice patterns found in stores are constructed on the basis of a B cup. Based on this principle, we therefore conclude that all other cups deserve to be adapted to the bust.

Let's first start by defining some important terms discussed in this tutorial.

- Cup : difference in measurement between the upper chest and the chest circumference.

- Upper chest : line passing above the chest and flush with the armpits.

- Chest circumference : line passing through the tip of the breast, also called the protrusion, at the strongest point of the chest.

Depending on the cap, the difference is equal to:

2.5 cm - A cup

5 cm – B cup

7.5 cm – C cup

10 cm – D cup

Example 1:
Upper chest circumference: 85 cm

Chest circumference: 89 cm

Difference between the 2 measurements: 89 – 85 = 4 cm

Closest cup: B + 1 cm

In this case, it is not necessary to make any changes to the pattern.

Example 2:
Upper chest circumference: 88 cm

Chest circumference: 96 cm

Difference between the 2 measurements: 96 – 88 = 8 cm

Closest cup: C + 0.5 cm

In this case, it is necessary to make a modification to the pattern.

At this stage, it is therefore possible to define your bonnet and know if a transformation is necessary.

How to choose your pattern size?

For A, C and D cups, it is not advisable to choose your pattern size based solely on your bust measurement because the garment would not fully correspond to your own body shape.

It is therefore advisable to choose your size based on your upper chest measurement and not your chest circumference.

To do this, refer to the pattern's measurement table, always in the "Chest size" column. Note that the size chosen is always built on the basis of a B cup.

How to calculate the transformation measure?

The next step is to calculate the measurement to enlarge or reduce the pattern at the chest level, in order to adapt it to an A, C or D cup.

Here is the calculation to apply:
- cup corresponding to its morphology - cup B.
- Divide the measurement obtained by 2, in order to add only half to the half front pattern.

Let’s go back to our example 2 seen above:
Upper chest circumference: 88 cm.
Size to choose according to the measurement table: 38 designed for a B cup (i.e. 5 cm difference between the chest and the upper chest)
Measurement to add to the pattern: cup corresponding to your body shape – cup B = (cup C + 0.5 cm) – 5 cm = 8 cm – 5 cm = 3 cm/2 = 1.5 cm