Full Bust Costume Fitting

Commercial sewing patterns and most ready-to-wear costumes are drafted using a B-cup as the standard. If your full bust measurement is significantly larger than your high bust measurement — the gap between the two is your cup size — any pattern drafted to that standard will fit your shoulders and waist but be too small across the bust.

The result is predictable: the neckline gaps open, the side seams pull forward, the armholes feel tight, and the whole silhouette looks off. The fix isn't to buy a larger size — it's to add the right amount of fabric in exactly the right place.

The Full Bust Adjustment (FBA)

The FBA is the foundational alteration for any bodice pattern. It adds width at the bust apex without changing the shoulder width, neckline, or waist. The amount you add equals the difference between your full bust and high bust measurement — your cup depth.

• Measure your high bust (around the chest, above the bust) and full bust (at the fullest point)
• The difference is the amount to add — typically 1–3 inches for D–H+ cups
• Cut the pattern piece and spread at the bust apex; true up the dart to absorb the added ease
• Apply to bodice fronts, corset fronts, and any fitted top pattern piece

Dart Repositioning

After an FBA, the bust dart will need repositioning so it points toward your actual bust apex rather than the pattern's assumed position. A dart that misses the apex creates fabric bunching or drag lines. Rotate the dart seamline to aim directly at the fullest point of your bust.

Letting Out vs. Grading Up

For bought or rented costumes, the simplest fix is often letting out the side seams specifically at bust level rather than regrading the whole garment. Open the side seam from bust to waist, let out 1–1.5cm per seam, and re-sew. This gives targeted extra room without changing the rest of the fit.

Structural Support in the Pattern

Once the fit is correct, building support into the costume itself means you don't need a visible bra underneath. Boning channels, sewn-in cups, and a shelf bra construction are all achievable at an intermediate sewing level.