Small Bust Adjustment (SBA) Tutorial

While much attention goes to Full Bust Adjustments, many sewists need the opposite: a Small Bust Adjustment (SBA). If you have a smaller bust relative to your ribcage, patterns can have excess fabric that creates awkward folds and bubbling.

What is an SBA?

A Small Bust Adjustment removes width from a pattern at the bust area. It's the inverse of an FBA - instead of slashing and spreading, you slash and overlap the pattern pieces.

Signs You Need an SBA

Look for these fit issues:

• Excess fabric below the bust point
• Horizontal wrinkles across the bust
• Dart points ending far from your bust point
• Gaping at the neckline (downward, not outward)
• Pattern waist hits below your natural waist

Do You Need an SBA?

Use the same measurements as for FBA:

| Measurement | Purpose | |-------------|---------| | High Bust | Your pattern selection size | | Full Bust | Comparison measurement |

SBA is needed when:

Full Bust - High Bust < Pattern's built-in ease (usually 2")

Example:

• Full Bust: 36 inches
• High Bust: 35 inches
• Differential: 1 inch
• Pattern ease: 2 inches
• Result: 1 inch less than expected = SBA needed

Step-by-Step SBA Process

Step 1: Calculate the Overlap Amount

Overlap = (Pattern Ease - Bust Differential) / 2

Using our example:

• (2" - 1") / 2 = 0.5 inches per side

Step 2: Mark Your Apex and Slash Lines

Draw the same lines as for an FBA:

1. Vertical line from apex to waist
2. Horizontal line from apex toward armscye

Step 3: Slash and Overlap

Instead of spreading, overlap the pattern pieces:

• Close the vertical slash at the bottom
• The horizontal line will overlap slightly
• Tape securely

Step 4: True the Lines

After overlapping:

• Smooth the waist seam (it will need slight adjustment)
• Adjust side seam length
• The dart will decrease in size (or may be eliminated for very small busts)

SBA for Different Pattern Types

Darted Bodice

The standard SBA works perfectly. The dart intake will reduce proportionally.

Princess Seam Bodice

Overlap at the princess seam line instead of creating a dart adjustment. The seam itself provides the shaping.

Dartless Bodice

Some ease will be removed from the side seam area. Be careful not to remove too much or the bodice will be too fitted.

Digital SBA with Bombajom Patterns

Just like with FBA, Bombajom Patterns can calculate and apply your SBA automatically:

1. Upload your PDF pattern
2. Enter your measurements (full bust and high bust)
3. Mark your apex point
4. The system calculates and applies the overlap

Try it now and save time on your next project.

Frequently Asked Questions

Can I do an SBA on a multi-size pattern?

Yes! Select your size based on high bust measurement, then apply the SBA.

What if I need more than 1" SBA per side?

For larger adjustments, consider sizing down and doing an FBA to add back what you need elsewhere.

Does SBA affect the armhole?

Minimal impact if done correctly. The overlap happens below the armscye.

Related Articles

• Full Bust Adjustment Guide
• How to Measure for Pattern Adjustments
• Understanding Ease in Sewing Patterns