How to Do a Full Bust Adjustment (FBA) on a Woven Sewing Pattern
A full bust adjustment (FBA) adds extra shaping through the bust of a sewing pattern by creating a dart in the side seam.
An FBA will also add width through the waist and a little extra length to the front. So if you usually multi-size (blend between sizes) at the waist or lengthen a top, wait until after you've completed this adjustment.
Once completed, if you find you still need a little extra front length, see our Extra Front Length Adjustment tutorial.
Print the front shirt pattern pieces in the size corresponding to your upper bust measurement. Join the pages together and cut out the pattern.
DRAW IN THE DRAFTING LINES
Before cutting into your pattern, you'll need to draw five lines, labelled A–E, below.
Lines A, B and C are drawn from the bust apex. This is the small + marked on your pattern piece. If your pattern doesn't have one, measure on yourself (1) apex to apex & then divide by 2; (2) centre of shoulder to apex. Mark on your pattern.
Draw the following lines on the front pattern piece.
Cut along the drafting lines in the following order. Take care to leave the small hinges intact.
Place your pattern onto another sheet of paper. Tape the centre front section down, keeping the centre front and original Line A in position.
Calculate your adjustment.
First, find your size using your upper bust measurement, then find the size corresponding to your full bust measurement. Count the number of sizes between them.
Use the table below as a starting point for your FBA.
| Size difference | FBA adjustment |
|---|---|
| 1 size | 1.25cm (1/2") |
| 2 sizes | 2.5cm (1") |
| 3 sizes | 3.75cm (1 1/2") |
| 4 sizes | 5cm (2") |
Consider the fit of your pattern.
For a fitted or semi-fitted style, use the adjustment corresponding to your size difference. For an easy or relaxed fit, you may need less, so consider going down one adjustment level.
FOR EXAMPLE
Your upper bust measurement corresponds to a size 10, while your full bust corresponds to a size 16. That's a difference of three sizes.
Fitted or semi-fitted: Use the 3-size adjustment of 3.75cm (1 1/2").
Easy or relaxed fit: Consider the 2-size adjustment of 2.5cm (1").
These are suggested starting points. The amount of adjustment needed will depend on the style, included ease and your preferred fit.
On the new sheet of paper, draw a vertical line (F), parallel to Line A, at the width of your calculated adjustment.
Holding the lower side section (yellow), move the pattern piece until its right edge aligns with the new Line F.
As you move the pattern piece, you'll notice the armhole angle changes too.
Tape all the pattern pieces into position.
Widening the bust line also lowers the dart and the front hem.
To balance the front, cut along Line D and lower the section so the bottom of the cut lines A are even.
Tape the section into place.
Draw in the new bust dart.
Measure halfway between the new dart lines, then draw a line from the lowered apex through the centre of the dart.
Mark a new bust point (G) along this line, approximately 4–5cm (1.5–2") away from the new apex.
Draw the new dart legs from the side seam to the new bust point (G).
Shape the end of the dart.
We need to check the dart end so that the side seam will be the correct shape once the dart is sewn.
Fold the pattern along the lower dart line. Fold the lower line up to meet the upper dart line. The excess paper will fold downwards.
Keep the dart folded closed and cut along the outer edge of the new pattern piece to shape the side seam.
Open the dart back out. Your new dart is ready to sew.
Sew the bust darts before joining the side seams together.
