What Is a Full Bust Adjustment (FBA)?

A Full Bust Adjustment (FBA) is a pattern alteration that adds width to the bust area of a bodice pattern. It's one of the most common alterations in sewing — and one of the most dreaded, because traditionally it involves scissors, tape, and a lot of math.

Why Do You Need an FBA?

Most commercial sewing patterns are drafted for a B or C cup. If your cup size is larger, the pattern won't have enough room in the bust area. The result: pulling across the chest, the hem rides up in front, and the overall fit feels tight and uncomfortable.

An FBA solves this by:

• Adding width at the bust through a "slash and spread" technique
• Increasing the dart to accommodate the extra fullness
• Keeping everything else the same — shoulders, waist, and length stay at your correct size

The Traditional Way vs. the Digital Way

Traditional (30+ minutes)

1. Print your pattern pieces
2. Draw slash lines from the armscye through the bust point to the hem
3. Cut along the lines with scissors
4. Spread the pieces apart by the calculated amount
5. Tape tissue paper underneath
6. Redraw ("true") the seam lines
7. Re-cut the pattern

Digital with Bombajom (2 minutes)

1. Upload your PDF pattern
2. Enter your high bust and full bust measurements
3. The system calculates the adjustment and applies it
4. Download your adjusted pattern

How to Know If You Need an FBA

Take two measurements:

• High bust: Measure around your torso just above the fullest part of your bust
• Full bust: Measure around the fullest part of your bust

Calculate: full bust - high bust = bust differential

| Bust Differential | What It Means | |---|---| | Less than 5 cm (2") | You may need an SBA instead | | 5-7 cm (2-2.75") | Standard — no adjustment needed | | More than 7 cm (2.75"+) | You need an FBA |

Try It Yourself

Ready to apply an FBA to your own pattern? Bombajom makes it automatic — upload any PDF pattern, enter your measurements, and download an adjusted pattern in minutes.

Start your free trial →

Further Reading

• How to Measure for a Bust Adjustment
• Step-by-Step FBA Tutorial
• Small Bust Adjustment (SBA) Guide