A Full Bust Adjustment (FBA) adds the extra width and length a pattern needs to fit a fuller bust without changing the fit through the shoulders and upper chest. The adjustment can be made to both darted and dartless bodice patterns, using different methods.
In this guide, you’ll learn how to tell whether you need a Full Bust Adjustment, determine how much extra room to add, and adjust both darted and dartless bodice patterns. We’ll also cover how to check the bust apex, reshape the dart, and true the altered pattern so your finished pieces fit together properly. If you’re working with a Winslet’s sewing pattern, these same fitting principles can help you make adjustments that better suit your measurements and preferred fit.
What Is a Full Bust Adjustment?
A Full Bust Adjustment is a pattern alteration used when the bust area needs more room than the pattern provides. It is particularly useful when you choose your pattern size according to your high bust measurement but find that the finished bodice is too tight across the bust.
Choosing a size using the high bust rather than the full bust can give you a better fit through the upper chest and shoulders. However, it can also mean that you need additional room at the bust. An FBA adds that room where it is needed rather than simply sizing up the entire bodice.
How do you know if you need an FBA?
Look for signs that the bust is pulling the fabric forward. Common signs include:
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Diagonal lines of strain pointing toward the bust.
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The front hem sitting higher underneath the bust than at the side.
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Side seams pulling toward the front.
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A bodice that feels tight across the bust even though the shoulders and upper chest fit well.
You can also compare your high bust and full bust measurements with the measurements the pattern was drafted for.
How Much Should You Add for a Full Bust Adjustment?
The amount you add depends on the difference between your body measurements and the pattern's measurements, including the ease you want in the finished garment.
In pattern drafting, the "cup size" refers to the difference between the high bust and full bust measurements—not your bra cup size. A 1-inch difference corresponds to a pattern A cup, 2 inches to a B cup, and 3 inches to a C cup, continuing in the same way.
Check what cup size the pattern was drafted for before deciding how much to add. You can also compare your body measurement plus your desired ease with the finished garment measurement if the pattern provides one.
For example, if your measurements indicate a 3-inch difference but the pattern is drafted for a 2-inch difference, you may need to add an additional inch at the bust.
Don't forget about ease
Ease is the extra room built into a garment beyond the body measurement. Wearing ease provides the room needed to move, while design ease creates additional volume for styles such as oversized or swing garments.
The minimum bust ease given in the source guide is:
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Blouses, dresses and jumpsuits: 2½–3 inches (6–7½ cm)
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Unlined jackets: 3–4 inches (7½–10 cm)
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Lined jackets: 3½–4½ inches (9–11½ cm)
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Coats: 4–5 inches (10–12½ cm)
The amount of wearing ease also depends on the fabric and garment. Thicker fabrics and garments designed to be worn over layers generally require more room.
Check the Bust Apex Before Making an FBA
The bust apex is the fullest point of the bust, and the pattern's apex should ideally line up with yours. Check the apex location before making the adjustment because the bust dart or shaping may need to be raised or lowered first.
If the pattern has a marked apex, use that as your reference. If it does not, the dart generally points toward the apex, although its tip will sit away from the actual bust point.
You can find your body measurements by measuring from the mid-shoulder to the fullest point of the bust and then from the fullest point across to the other side. Transfer these measurements to the pattern while excluding seam allowances.
Once the apex is established, measure the pattern across the bust at that level. Fold out the dart while measuring if necessary, and exclude seam allowances. Compare the complete front and back pattern measurements with your body measurement plus your desired ease.
If you need more than 4 inches of total additional room, the FBA alone will distort the pattern too much. In that case, another type of alteration is needed as well.
How to Do a Full Bust Adjustment on a Darted Bodice
A darted bodice uses the slash-and-spread method. You cut into specific areas of the pattern, spread the pieces to add width at the bust, and then reshape the dart and surrounding seams.
Step 1: Mark the adjustment lines
Start with a copy of your bodice pattern and mark your bust apex.
Draw three lines:
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Draw a line parallel to the grainline from the apex to the waist or hem.
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Draw a line from the apex to a point in the lower third of the armhole.
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Draw a line through the middle of the dart toward the apex.
The line through the dart does not necessarily need to end at the original dart tip because the dart will be redrawn later.
Step 2: Cut the pattern
Cut from the waist or hem to the apex. At the apex, turn and continue cutting toward the armhole, stopping just before the edge so a small paper hinge remains.
Cut along the dart line from the side seam toward—but not through—the apex, leaving another hinge.
Place a piece of paper underneath the pattern and secure part of the centre edge so the pattern stays in position.
Step 3: Add the required bust width
Spread the pattern horizontally at the apex by half the total amount you need to add.
For example, if your finished bodice needs 2 inches of additional bust room, add 1 inch to this half of the front pattern.
Keep the cut edges parallel as you spread them, then secure the pattern in place near the apex.
The dart will automatically open as the pattern spreads.
Step 4: Restore the hemline
Adding width at the bust also creates extra length across the front. This is necessary because the fabric now needs to travel over the fuller bust.
Bring the centre section of the pattern down until the bottom aligns with the side section. Keep the centre front or grainline aligned while doing this, then tape the pieces together.
Check that the bottom seam is smooth and that the armhole remains smooth.
Step 5: Redraw the dart
The dart needs to be reshaped after the adjustment.
Measure the original top dart leg. Bring the new dart point down toward the centre while keeping the dart-leg lengths equal. Then draw the new lower dart leg to match the top leg.
The bust apex itself remains in its correct position.
Step 6: True the seams
Fold the dart closed by bringing the lower dart leg up to meet the upper leg. Check the side seam.
If the side seam is uneven after folding the dart, redraw it as a smooth line. Remove excess from the longer side and add to the shorter side as needed.
This process is called truing the pattern.
With the dart folded, cut along the new side-seam line. Then refold the dart and check the front against the back at the side seam. True the seam again if necessary.
The waist measurement will have increased because the bodice was expanded. If you do not want or need that additional waist room, it can be removed from the side seam.
How to Do a Full Bust Adjustment on a Dartless Bodice
A dartless bodice can be adjusted using a simpler pivot method. Instead of creating a permanent bust dart, you pivot the pattern to add the required room.
Step 1: Trace the pattern
Trace your bodice onto another piece of paper. Mark the seam allowances at the shoulder and armhole.
Step 2: Mark the amount to add
At the armhole side seam, measure inward by half the total amount you need to add at the bust and mark that point.
For example, if you need 2 inches more across the bust, mark 1 inch on this half of the front.
Step 3: Pivot the pattern
Hold the pattern at the intersection of the shoulder and armhole seams. Pivot the pattern outward until the underarm reaches your new mark.
Trace the new position to create the adjusted armhole.
Then move your pencil or pen down to the armhole and side-seam intersection and use it as the pivot point. Pivot the pattern back until the side seam meets the original side seam at the waist or hem.
Trace the new side seam.
Step 4: Check the side seam
The side seam may need to be raised at the waist to maintain its original length. Compare the adjusted front with the back pattern piece at the side seam to make sure the two pieces remain equal and true.
Can a Full Bust Adjustment Change the Dart Position?
Yes. Dart position can have a significant effect on fit, particularly in styles that already have a lot of design ease. A dart can be positioned closer to or farther from the bust apex, or moved higher or lower.
If the garment already has plenty of design ease, you may not need to add as much extra room as you would to a close-fitting style. Before making an FBA, make sure the pattern's bust apex is positioned correctly for your body.
If you'd like to see the adjustment demonstrated step by step, you can watch the visual tutorial below, which covers both darted and dartless bodice adjustments.
Ready to Work On Your Next Pattern?
A well-planned FBA can make a significant difference when the shoulders and upper chest fit but the bust needs additional room. Once you understand where to measure, how much to add, and how to true the altered pattern, you can approach fitted bodices with much more confidence.
If you're ready for your next sewing project, explore Winslet's collection of digital sewing patterns and choose a style you can adapt to your measurements and preferred fit.
FAQs
What is the difference between an FBA and simply going up a size?
An FBA adds room specifically where it is needed at the bust. Simply sizing up can make the shoulders and upper chest too large when those areas already fit correctly.
How do I know how much to add to an FBA?
Compare your body measurement plus your desired ease with the pattern's finished garment measurement. The difference tells you how much additional room you need. Remember that each half-front pattern receives half of the total amount.
Does an FBA work on a pattern without a bust dart?
Yes. A dartless bodice can be adjusted using the pivot method, which adds the required bust room without creating a permanent dart.
Should I check the bust apex before making an FBA?
Yes. The pattern's bust apex should correspond closely with your own. If it needs to be raised or lowered, make that correction before performing the FBA.
Can I add as much room as I need with an FBA?
No. The adjustment has limits. If more than 4 inches of total additional room is needed, another alteration should be combined with the FBA rather than adding all of the extra width through the FBA alone.
