A full bust adjustment (FBA) is a pattern alteration that adds length and width exactly where a full bust needs them, while leaving the neck, shoulders, armhole and waist at the size that already fits. Most patterns are drafted for a B cup; a wearer with a larger cup who simply sews a bigger size gets a garment that fits the bust but swims at the shoulders. The FBA instead spreads the front pattern through the bust point, creating the extra fabric a fuller bust requires and enlarging or adding a dart to shape it.
How an FBA Works
On a darted bodice, three slash lines are drawn through the bust point — to the armhole, down to the hem and across to the side dart — and the front is spread open by the amount the bust measurement is short, pivoting at the armhole so the shoulder does not move. The side dart grows, front length increases so the hem levels, and the side seam is re-trued. On princess seams the same spread is made on the front panel; on dartless styles the spread adds width and a dart or easing may be introduced.
- Sewing — the Apparel Search sewing section
- How much to add — roughly 1 inch (2.5 cm) of bust circumference per cup size above the pattern's drafted cup, worked out from the difference between full-bust and high-bust measurements.
Signs You Need One
A fitting shell or muslin that strains across the bust, pulls its buttons, lifts the front hem, points its darts away from the apex or drags diagonal wrinkles toward the bust is asking for an FBA — not a bigger size. The companion alteration, the small bust adjustment, removes the same wedge for a smaller cup.
Two refinements separate a good FBA from a rough one. First, the added length must run down the whole front, so the front waist and hem drop to level — a common beginner's miss that leaves the front hem hiking up even though the bust now fits. Second, the enlarged dart often needs its point repositioned to aim exactly at the new apex, which may sit lower or further out than the pattern assumed. On wrap styles and empire lines the same spread is applied below the style seam, keeping the adjustment invisible in the design.
FAQs
- Should I just sew a larger size for a full bust?
- Usually not. A larger size enlarges the neck, shoulders and armhole too. An FBA adds room only at the bust, so the frame of the garment still fits.
- Why does an FBA make the dart bigger?
- The added width must be shaped back to the waist. The dart is the shaping, so it grows by exactly the amount of fullness added over the bust.
- How do I know the pattern's drafted cup size?
- Many patterns state it; standard drafting is a B cup, meaning the full bust measures about 2 inches (5 cm) more than the high bust. Compare with your own difference.
Detailed Guides: see Full Bust Adjustment in the glossary A–Z listing of the Apparel Search fashion glossary for related terms.