title: "How to Do a Small Bust Adjustment (SBA) on Any Bodice Pattern" description: "Learn how to do a Small Bust Adjustment (SBA) on any bodice pattern using Bombajom's digital tools. Reduce excess ease for a better fit." difficulty: beginner adjustmentTypes:

sba patternTypes:
bodice-front estimatedTime: "10 minutes" prerequisites:
measurements/how-to-measure-for-bust-adjustment

How to Do a Small Bust Adjustment (SBA)

A Small Bust Adjustment (SBA) is the reverse of an FBA — it removes excess fabric from a bodice pattern when your full bust measurement is smaller than the pattern's intended ease. If you find yourself with gaping fabric at the bust, a droopy bustline, or too much room in the bodice front, an SBA is the fix.

When Do You Need an SBA?

You need an SBA when your bust differential (full bust minus high bust) is less than the pattern's built-in ease. Most patterns are drafted for a B/C cup. If you have a smaller cup size, the pattern has too much room in the bust area.

The math:

Measure your high bust (above the fullest part of the bust)
Measure your full bust (at the fullest part)
Calculate: full bust - high bust = your bust differential
If your differential is less than the pattern's ease (typically 5 cm / 2"), you need an SBA

How Bombajom Calculates Your SBA

When you enter your measurements in Bombajom, the system automatically:

Calculates the bust differential from your high bust and full bust measurements
Compares against the pattern's ease to determine how much fabric to remove
Locates the apex point (bust point) on your pattern piece
Applies the SBA — overlapping the pattern along slash lines through the apex, reducing width precisely

The result is a pattern that fits your smaller bust without the excess ease that causes gaping and poor fit.

Step-by-Step in Bombajom

1. Upload Your Pattern

Upload your PDF sewing pattern. Bombajom analyzes the structure and identifies the bodice front piece.

2. Enter Your Measurements

Enter your high bust and full bust measurements. The system calculates your bust differential automatically.

3. Mark or Confirm the Apex

Bombajom's auto-detection places the apex point. You can adjust it if needed by clicking directly on the pattern.

4. Review the Recommendation

The system shows you the calculated SBA amount. Review the spread amount and confidence level before applying.

5. Apply and Download

Click "Apply" to see the adjustment preview, then download your modified pattern as a print-ready PDF.

Tips for a Better SBA

Always use your high bust measurement to select your pattern size, then apply an SBA for the bust area
Check the seam allowance — Bombajom preserves seam allowances, but verify they look correct in the preview
Make a muslin first — even with a digital adjustment, a test garment confirms the fit before cutting good fabric

FAQ

Q: How is an SBA different from just using a smaller size? Going down a size changes the entire pattern (shoulders, waist, length). An SBA only changes the bust area, keeping everything else at your correct size.

Q: What if my pattern has princess seams instead of darts? The SBA works on princess seam patterns too. The overlap is distributed along the princess seam rather than closing a dart.

Next Steps

New to bust adjustments? Start with How to Measure for a Bust Adjustment
Need the opposite? Learn about Full Bust Adjustment (FBA)
Ready to try? Open the editor and upload a pattern