Full Bust Adjustments on Knit Sewing Patterns

When sewing garments for a fuller bust, Full Bust Adjustments (FBAs) can make all the difference in achieving a comfortable and flattering fit. In this guide, we’ll use the Breastfriend Bralette as an example and discuss two methods:

  1. Adding darts to the side seams 
  2. The more "quick and dirty" approach.

Tip: Always make a toile (test garment) using a knit fabric with similar stretch and recovery as your intended fabric. The fit can also be influenced by whether or not you use elastic in your seams and the density of that elastic. 

Both methods are illustrated below.

Method 1: Adding Darts

Step 1: Measure and Determine the Adjustment Needed

  1. Measure Your Full Bust: Measure around the fullest part of your chest.
  2. Measure Your High Bust: Measure above your bust, under your arms.
  3. Calculate the Cup Difference:
    • Subtract your high bust measurement from your full bust measurement.
    • A 2" difference = B cup (standard for most patterns).
    • Each additional inch increases the cup size (e.g., 3" = C cup, 4" = D cup, etc.).
  4. Determine the Total Adjustment:
    • Find the difference between the pattern’s intended full bust measurement and your actual full bust measurement.
    • Divide this number by 2 (since the pattern represents only half your body).
    • This result is your adjustment amount, which we’ll refer to as "X".

Step 2: Locate the Bust Point

  • On the front bodice piece, locate the apex (bust point).
  • If it’s not marked, it’s usually the fullest part of the curve on the side seam (where the nipple would align).
  • Mark this point.

Step 3: Draw Guidelines for the Adjustment

  1. Draw three lines on your pattern piece:
    • Line A: From the bust point straight down to the hem (parallel to the grainline).
    • Line B: From the bust point straight out to the side seam (perpendicular to the grainline).
    • Line C: From the bust point up to the armhole curve, stopping about 1/3 of the way into the armhole.

Step 4: Slash and Spread

  1. Cut Along the Guidelines:
    • Cut along Line A from the hem to the bust point, then to the armhole (Line C). Stop at the seam allowance to leave a hinge.
    • Cut along Line B from the side seam to the bust point, stopping at the seam allowance to leave a hinge.
  2. Spread the Pattern:
    • Gently spread the pattern along Lines A and B.
    • Add the required width for your adjustment (calculated as "X" in Step 1).
    • Ensure the side seam remains even, and the hem stays straight.

Step 5: Re-Shape the Pattern

  1. Fill the Gaps: Use extra pattern paper to fill in the spaces created by the adjustment and tape them in place.
  2. True the Armhole Curve: Smooth out any jagged lines.
  3. Redraw the Side Seam and Hemline: Ensure they are even and straight.

Step 6: Check the Hemline and Length

  • Smooth the Hemline: Trim any excess length to ensure it’s even.
  • Adjust the Dart: Slightly curve the dart towards the apex for a better shape.

Step 7: Test the Fit

  • Cut and Baste: Create a muslin or test garment from your adjusted pattern.
  • Evaluate the Fit: Ensure there’s enough room across the bust, and the side seams hang straight.

Key Tips

  • Knit fabrics have stretch, so FBAs may require less adjustment compared to woven fabrics.
  • Ensure the fabric’s stretch percentage matches your pattern requirements to prevent distortion.
  • Patterns for knit tops without darts may not need as dramatic of an FBA due to the fabric’s flexibility.
  • Sew the darts with a lightening bolt stitch (or narrow zig-zag) to ensure it stretches.

Method 2: The 'Quick and Dirty' Approach

For this method, you’ll increase the chest coverage by straightening out the neckline and armscye curves.

This approach is faster and works well for knit fabrics with plenty of stretch. See the illustration below for guidance.

Back to Tips & Tricks