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How to do a full bust adjustment (FBA) on princess seams // A Karri dress tutorial

How to do a full bust adjustment FBA on princess seams // shown on Megan Nielsen's Karri dress sewing pattern

I’ve heard from a lot of people that they find the idea of doing a bust adjustment on princess seams horrifying. Honestly, it’s actually not that different than doing a bust adjustment on a darted bodice – but personally, i feel like you get a smoother end fit with princess seams. With the release of my new Karri dress, I knew many of you would be wondering how to tackle this adjustment, and also whether in fact you actually need one. But never fear! You can do it, i promise.

Here’s the deal. Most patterns are drafted for a B cup. I know that’s probably upsetting those of you who aren’t B cups, but the unfortunate truth is that patterns need to be drafted to some sort of base standard, and most pattern companies (like mine) draft for a B cup. What does this mean for people who aren’t B cups? Well, you’ll probably need to alter your pattern to get the right fit over your bust.

How to do a full bust adjustment FBA on princess seams // shown on Megan Nielsen's Karri dress sewing pattern

So how do you know if you need to do an FBA on your pattern? There are a couple of ways you can tackle this, but here is my easy method. You know that size chart you get on the back of your pattern envelope? If you find that your bust measurement falls in a larger size column than the rest of your body – then you’ll probably need to do an adjustment. If you’ve already made a muslin, you might notice you need to do an FBA because things just aren’t quite sitting right in that area. Some symptoms may include:

  • the waistline being higher at the front than the back of your bodice
  • the fabric pulling around your arm syce
  • an inability to close the bodice of your dress around your bust, even though you can over the rest of your body
  • the apex hitting you too high
Ok cool. So now we know if we need one. Shall we begin the alteration?

// CALCULATE //

How to do a full bust adjustment FBA on princess seams // shown on Megan Nielsen's Karri dress sewing patternCalculating the size of your adjustment is really easy if you use this simple method. Just figure out what size you would be if you used your bust measurement – then compared it to what size you would be if you used your other measurements to determine your size. The difference between these two measurements is the size of your FBA.
Say for example you have a bust measurement of 42″ (107cm) which is a size XL, but your waist and hip are firmly in the L measurement range. Well you probably need an FBA. Your total FBA amount would be the difference between the XL and L bust sizes, so 2″ (5cm). You now need to divide this in half, and this is the amount you will adjust the pattern piece by. So in our example, it would be a 1″ (2.5cm) adjustment.

DRAW SLASH LINES

How to do a full bust adjustment FBA on princess seams // shown on Megan Nielsen's Karri dress sewing pattern How to do a full bust adjustment FBA on princess seams // shown on Megan Nielsen's Karri dress sewing pattern
Now the fun part. Lets draw some crazy lines all over our patterns. Kidding. They’re not crazy, they have very specific purposes
  1. First note the notch on the CF of the Side Bodice pattern. On Karri this conveniently corresponds to the bust apex. Mark a point 5/8″ (1.5cm) in from this point, as we don’t want to adjust in the seam allowance.
  2. Next draw a line from this point to your armsyce, about 1/3 of the way in. Conveniently, the notch on the armsyce are pretty much 1/3 of the way up. Make sure that you mark 5/8″ (1.5cm) in from the armsyce edge.
  3. Draw a line down from your centre bust straight down – alone the grainline. This line should be parallel to the grainline marking on the pattern. Unfortunately this line has ended up in the seam
  4. Draw a short line perpendicular to line 3 . This line should hit the Line 3 and edge of the pattern

CUT & SPREAD

How to do a full bust adjustment FBA on princess seams // shown on Megan Nielsen's Karri dress sewing pattern

Cut Line 3 from the bottom to the centre bust, then along Line 2 till you reach the dot you marked near the armsyce, making sure not to cut completely through the pattern paper at the armsyce. Also cut the seam allowance towards the seamline dot. We need to leave a little bit so that we can use it as a hinge.

How to do a full bust adjustment FBA on princess seams // shown on Megan Nielsen's Karri dress sewing pattern

Next cut Line 1 from the side seam towards the centre bust. Do not cut completely through the pattern paper at the center bust. Once again, we want to leave a bit of paper to use as a hinge.

How to do a full bust adjustment FBA on princess seams // shown on Megan Nielsen's Karri dress sewing patternHow to do a full bust adjustment FBA on princess seams // shown on Megan Nielsen's Karri dress sewing pattern

Spread the centre slash line (line 3) by the size of your bust adjustment. Make sure you keep the slash lines parallel (ie keep the distance the same all the way down). For this example i’m going to use an adjustment of 1″ (2.5cm) as calculated above.

How to do a full bust adjustment FBA on princess seams // shown on Megan Nielsen's Karri dress sewing pattern

Now we need to fix the waistline. The centre front is now slightly shorter. Cut along line 4, cutting completely through – then move it down till it is in line with the new waistline. I like to use my ruler to keep it straight.

How to do a full bust adjustment FBA on princess seams // shown on Megan Nielsen's Karri dress sewing pattern

Put some pattern paper underneath, and tape everything together!!

How to do a full bust adjustment FBA on princess seams // shown on Megan Nielsen's Karri dress sewing pattern

Now we have made our adjustment, but we’ve added a dart at the side seam, which we don’t want. So we need to eliminate it, but keep the extra ease.

Extend line 1 all the way to the centre front of the pattern.

How to do a full bust adjustment FBA on princess seams // shown on Megan Nielsen's Karri dress sewing pattern

Cut open the dart, and also cut along the new line we have created at the centre front, being careful to leave a small amount of paper to act as a hinge.

How to do a full bust adjustment FBA on princess seams // shown on Megan Nielsen's Karri dress sewing pattern

Close the side seam dart and tape together. You’ve now moved the dart excess to the centre front!

How to do a full bust adjustment FBA on princess seams // shown on Megan Nielsen's Karri dress sewing pattern How to do a full bust adjustment FBA on princess seams // shown on Megan Nielsen's Karri dress sewing pattern How to do a full bust adjustment FBA on princess seams // shown on Megan Nielsen's Karri dress sewing pattern How to do a full bust adjustment FBA on princess seams // shown on Megan Nielsen's Karri dress sewing pattern

Having a look at our adjusted pattern piece you can see that we have made the side front pattern piece longer. This means we will also need to lengthen the centre front pattern pieces. On a standard princess seam dress, the adjustment would look like this. Measure the additional length you added to the side front panel, and transfer these to the centre front pattern piece. First mark your cut lines, then spread them by the appropriate amounts, tape extra paper in the gaps, and cut out your new pattern.

//KARRI SPECIFIC ADJUSTMENT//

How to do a full bust adjustment FBA on princess seams // shown on Megan Nielsen's Karri dress sewing patternHow to do a full bust adjustment FBA on princess seams // shown on Megan Nielsen's Karri dress sewing pattern How to do a full bust adjustment FBA on princess seams // shown on Megan Nielsen's Karri dress sewing pattern How to do a full bust adjustment FBA on princess seams // shown on Megan Nielsen's Karri dress sewing pattern

For Karri the Front of the bodice is made of 3 panels. The easiest way to extend the front of the bodice, is to adjust the front pattern piece, labeled number 1 only. Since all of our adjustments happened below the bust notch on pattern piece 4, we can essentially ignore pattern piece 2, the front top. However please keep in mind that though this is the simplest way to adjust the pattern, it will mean that the horizontal bust seamline in the pattern will sit higher than the bust apex. In the original pattern this line goes directly through the bust apex. You may like this look with the style line higher, but if you prefer the seam to hit across the bust apex as in the original pattern, than i would suggest a further adjustment.

How to do a full bust adjustment FBA on princess seams // shown on Megan Nielsen's Karri dress sewing pattern

Choose a new notch location on pattern piece 4, that corresponds with the bust apex. You will need to test this on yourself, but for this example I’m using the top leg of the adjustment dart.

How to do a full bust adjustment FBA on princess seams // shown on Megan Nielsen's Karri dress sewing patternHow to do a full bust adjustment FBA on princess seams // shown on Megan Nielsen's Karri dress sewing pattern

Cut off the seam allowance at the notch on pattern piece 2. Discard the seam allowance, and tape pattern piece 2 on top of pattern piece 1 so that the notch lines up. Draw the new notch location on pattern piece 1, in this example it will be the top cut line.

How to do a full bust adjustment FBA on princess seams // shown on Megan Nielsen's Karri dress sewing pattern

Cut along this line. These are your new pattern piece 1 and 2. Don’t forget to add seam allowance to the top of pattern piece 1, and bottom of pattern piece 2.

//FINAL NOTE//

Now one last note.In this tutorial I didn’t want to complicate things, so I have shown the standard method for an FBA. This standard approach will always result in making the waistline wider in addition to the bust. This means that you will more than likely need to remove some width from the side seams of pattern piece 4  to maintain your correct size. My personal method for this differs very slightly. Instead of maintaining the entire bust adjustment for the full length of bodice, i keep the bottom edge of cut line 3 hinged, to remain the waistline, and only expand the bust apex by the FBA amount.

Don’t have the Karri sewing pattern yet? Get it in store here! We absolutely love seeing what you make, so don’t forget to tag your creations with #MNkarri and @megannielsenpatterns if sharing on social media.

Happy sewing!

Karri dress sewing pattern envelope

About Author

Meg is the Founder and Creative Director of Megan Nielsen Patterns, and is constantly dreaming up ideas for new sewing patterns and ways to make your sewing journey more enjoyable! She gets really excited about design details and is always trying to add way too many variations to our patterns.

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[…] Megan Nielsen demonstrates a full bust adjustment on princess seams. […]

Toni
5 years ago

Would I need to do a SBA for an A cup? If so…how??!!

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[…] How to do a Full Bust Adjustment on princess seams […]

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[…] How to do a Full Bust Adjustment on princess seams […]

Meg White
5 years ago

As you mention, this tutorial leaves you with lots of room added to the waist. As described, it also won’t match up to the waistline of the skirt. I’d love to see the way you actually do your FBA to fix this. I’ve looked at these two tutorials (http://byhandlondon.com/blogs/sew-alongs/11628649-elisalex-dress-sewalong-2-full-bust-adjustment-for-princess-seams-fba and http://www.idlefancy.com/2014/01/sewing-curve-fba-for-princess-seams.html) that address the waist measurement by slanting the side-seam in. Does that affect the grain line? Is that a problem? How is your way different? I think you are saying that you slant it in along the princess line. Cool, this would make sense since you can see right there exactly how much to take out of the waist. Is that better for the grain line? I’m very interested in FBA information, having a rather FB myself. Thanks, Megan, for all your expertise! This pattern is super cute.