How to Do a Full Bust Adjustment on Any Bodice Pattern

A Full Bust Adjustment (FBA) is one of the most common pattern modifications home sewists need. If you've ever had a garment pull across the bust, gap at the armhole, or ride up at the front hem, you likely need an FBA.

What You'll Need

• Your high bust and full bust measurements
• A bodice pattern (PDF)
• A Bombajom account (free trial available)

Step 1: Take Your Measurements

The two measurements that determine if you need an FBA are:

High Bust: Measured around the chest, just under the arms and above the bust fullness. The tape should be snug but not tight.

Full Bust: Measured at the fullest point of the bust, keeping the tape parallel to the floor.

The difference between these two numbers is your bust differential. If it's greater than 5 cm (2 inches) for a standard-ease pattern, you need an FBA.

Example: If your high bust is 88 cm and your full bust is 96 cm, your bust differential is 8 cm. After subtracting the pattern's built-in ease (typically 5 cm), the FBA would add 3 cm of width.

Step 2: Upload Your Pattern

1. Go to the Bombajom editor
2. Click Upload Pattern and select your PDF
3. Wait for the pattern to load

Step 3: Enter Your Measurements

1. In the right panel, enter your high bust and full bust measurements
2. The calculator will automatically show the bust differential and recommended spread amount
3. If the spread amount is less than 0.5 cm, no adjustment is needed

Step 4: Mark the Apex Point

The apex (bust point) is the fullest point of the bust on the pattern.

1. Click Mark Apex Point
2. Click on the pattern where the apex should be
3. Not sure where the apex is? Click the Help button for a visual guide

Tip: On most commercial patterns, the apex is approximately 2.5 cm (1 inch) below the dart point and 2.5 cm toward center front.

Step 5: Apply the FBA

1. Review the calculation summary — it shows the spread amount and dart increase
2. Toggle the Preview to see what the adjustment looks like
3. When you're happy, click Apply FBA

Step 6: Export Your Adjusted Pattern

1. Click Export in the toolbar
2. Choose your preferred format (PDF for printing, or projector format)
3. The calibration square on the exported PDF lets you verify the scale is correct

Common Questions

Q: My spread amount seems too large. Is that right? Double-check your measurements. Have someone help you to ensure the tape is level and snug. A spread of 3–5 cm is typical; anything over 7 cm is unusual.

Q: What if I have a princess seam instead of a dart? The FBA works on princess seam patterns too! The spread is distributed along the princess seam line rather than creating a wider dart.

Q: Do I need to adjust the back piece too? Usually not for an FBA. The back piece stays the same — only the front is adjusted.

Next Steps

• Learn about the reverse: Small Bust Adjustment (SBA)
• Read about ease and how it affects your FBA (guide coming soon)
• Try an FBA on a princess seam bodice (princess seam tutorial coming soon)