Patterns are drafted for a specific cup size (often a B‑cup).

This means the full bust measurement on the size chart assumes a certain high‑bust‑to‑full‑bust difference.

So:

1. Measure your high bust.

2. Choose the pattern size whose full bust measurement is closest to your high bust measurement.

This gives you the size that will fit your shoulders, neckline, and upper chest correctly.

Look at the size chart and note the full bust measurement for the size you just selected.

If the pattern doesn’t list a drafted high bust, you already added the correct section earlier:

Estimate the drafted high bust by subtracting 2" (5 cm) from the pattern’s full bust.

But for calculating the SBA amount, you only need the pattern’s full bust for your chosen size.

Now calculate the difference:

Pattern full bust (your size) − Your full bust = excess room

This tells you how much fabric needs to be removed for the bodice to fit your bust comfortably.

Because the pattern piece represents half your body, divide the total difference by 2.​

This gives you the amount to remove to the pattern piece itself.

Your high bust: 90 cm

Your full bust: 92 cm

​

The pattern is drafted for a B‑cup, which assumes a 5 cm difference between high bust and full bust.

​

1. Choose your size by high bust

You look at the size chart and choose the size where the pattern full bust = 96 cm, because:

• Pattern drafted full bust (96 cm) − assumed 5 cm = drafted high bust 90 cm, which is the closest to your 91 cm high bust.

This gives you the correct size for your shoulders and upper chest.

2. Compare your full bust to the pattern’s full bust for that size

Your full bust: 92 cm

Pattern full bust (your chosen size): 96 cm

96−92=4 cm total excess

3. Divide by 2 (because the pattern is half the body)

4÷2=2 cm per side

👉 You will remove 2 cm in your SBA on the pattern piece.