How to do a Full Bust Adjustment on a Dartless Shirt
A very useful pattern alteration to add to your skillset: a Full Bust Adjustment (FBA) for a dartless shirt. This one can be used when you’re making the Onyx Shirt, but can be used on any sort of bodice without darts, in both knits and woven fabrics. I’ll show you the FBA on View A of the Onyx shirt, you can find the tutorial for View B here. If you have any questions, let me know in the comments. Before you start, please read When Do You Need a Full Bust Adjustment to decide whether you need and FBA to begin with.
A full bust adjustment on a dartless shirt is done by slashing and spreading the pattern out until you have the extra width and length across the bust that you need. This creates a new bust dart, that you can then leave in or take out by slashing again and moving the side seam back in.
What you need
- front pattern piece of a pattern without darts (like the Onyx)
- straight ruler
- extra pattern paper
Step 1: Prepare pattern piece
Start with drafting in the seam allowances on the armhole and side seam. They are 5/8″ (1.5 cm) for the side seam and 3/8″ (1 cm) for the armhole on the Onyx Shirt. Then hold the pattern piece to your body and determine your apex (that’s Latin for peak or top, so in this case a fancy word for nipple). Mark it on the pattern.
Step 2: Draft and shift
Starting from the apex mark, draft a line towards the side seam (red line 1). Draft a second line from 1/3 of the armhole to the apex and then straight down to the hem (green line 2). Draft a third line (blue line 3) from the center front to the green line.
- Cut the green line from the hem to the apex and up to the armhole stitching line (yellow dot).
- Cut the armhole seam allowance to the yellow dot, but not completely through.
- Cut the red line from the side seam to the apex, but not completely through.
- Cut the blue line.
Anchor the main piece while you shift the side seam down and right. Keep the pattern flat. The amount you create between the green lines should be half the amount you need. Keep the green lines parallel to each other. When you have that piece in place, anchor it and shift the blue one down until it matches at the hem.
Step 3: Fill
When you have your pieces in the right position, fill the gaps with extra pattern paper and tape them down.
If you would do an FBA on a bodice with a bust dart, you would now have a larger bust dart then before. In this case we have created a dart where there wasn’t any. You have two options: you can redraft the dart and sew it, or you can eliminate the dart altogether. If you have added a lot in this FBA it might be best to leave the dart. Even in knits you can leave the dart in. It will give you a shirt that curves with your body instead of creating a boxy shape. But it’s a matter of personal preference, eliminating the dart might be preferable if you don’t want to break up a pattern in your fabric for instance.
If you want to keep the dart continue to Step 4, if not then continue to Step 5.
Step 4: Redraft dart
If you want to keep the dart, you have to redraft it. Draft two lines from the apex towards the side seam. Now make this triangle smaller, so the point is between 1 and 2″ (2.5-5 cm) away from your apex. Add a dart hat at the side seam so the side seam will line up when you sew the dart. This is the dart that you’ll sew. The grey areas in the illustration show where you’ve added room by making this adjustment.
Step 5: Redraft and cut out dart
If you want to eliminate the bust dart, you have to redraft it. Draft two lines from the apex towards the side seam (purple lines 4). Cut out the dart along these lines.
Step 6: Shift again
Cut along the green line 3 from the hem to the apex (yellow dot), but not through. Close the dart by pivoting at the apex. Tape in place.
Step 7: Redraft side seam
Since you now have an enormous waist dart, you have to redraft the side seam (pink line 5). It is easiest to take the original side seam to do this. Trace it on a piece of pattern paper and match the traced seam with the original. Stick a pin through the point where you closed the bust dart (yellow dot), and rotate the traced side seam clockwise. The amount you take off at the hem should be the same amount you added when you closed the bust dart. This is indicated by the arrows with the asterisk.
If you do not want to add any width to the hem at all, you can also take in this line further by redrafting it further inwards. Do not do this by pivoting or you will add too much at the armscye. Just redraft the side seam from the pivoting point down as you would when grading between sizes.
Fill up the little triangle at the armhole with pattern paper. Cut off the excess paper at the side seam. Trace the original hem line, redraft it and fill up the gap. The grey areas indicate where you have added room in the pattern.
Step 8: Pivot armscye
While you now have more room at the bust, the armscye has become larger. The last step is to pivot the armscye at the shoulder to meet the top of the pink line. This will prevent you from having to adjust the sleeve pattern. When you pivot at the shoulder, the point pivoting out will rise slightly. Re-draft the last part of the curve so it meets the top of the pink line. Check that the outer corner of the shoulder and the bottom corner of the armscye both have an angle of 90°.
You now again have a bodice without darts, but with more room at the bust as indicated by the red outline and grey areas in the illustration below.
Before you cut your fabric, measure the front and back side seams and add length to the back pattern piece. It’s quite an alteration, but worth it if it gives you a great fitting dartless shirt! If you have any questions, please leave a comment.
Other full bust adjustments
I’ve also written tutorials on full bust adjustments of other types of bodices:
- How to do a small full bust adjustment for princess seams
- How to do a large full bust adjustment for princess seams
- How to do a full bust adjustment on a pattern with waist darts
Thank you so much for sharing this, have just bought a shirt pattern from Grainline that I know I will need an FBA on, but feel darts will be a welcome addition for my 32FF bust. :-)
Glad to hear that – yes a dart will make in less boxy after the FBA.
Brilliant tutorial and very easy to understand, there are lots online for when you have darts but almost none for how to do an FBA when you don’t want darts (such as a basic knit t-shirt) Thank you
Thanks, glad it helped!
This may be a silly question, but do I need to alter the sleeve pattern at all, since with this method it adds about half an inch to the underarm? Or maybe I did something wrong?
Not at all a silly question! Yes you could. Add the same amount to the front side of the sleeve cap. Move the point where sleeve cap and sleeve seam meet out.
I’ve now included an extra step so you don’t have to alter the sleeve pattern.
How do you adjust back then?
Hi Trish, the back piece stays the same in shape, you just have to add length to the hem.
Hello, I’ve only done one FBA and it was kind of successful. What I’m curious about is that adding the bust dart in this way seems to add width and length to the front of the garment. I have a small waist in comparison to my bust and therefore don’t want to add any width there. Is there a method for reducing the width and length back to what it was before adding the dart, please? Appreciate any advice, thanks.
Hi W, it does add width and length: a bigger bust often needs that space because it pulls the fabric up and takes up more space width wise. I would be careful with removing this space. If you don’t want that at the side seam, you can redraw the side seam inward to the original width.
Hi again, thanks very much for your quick reply. Interesting about not removing the space – I hadn’t thought of it that way. I may have a go at doing the above then redrawing the side seam so that it goes back in at my waist on my next project.
You can always take it in after you’ve tried it on. Good luck!
Thank you for many years I have tried to find this information . Now I can have a shirt/bodice dart or dartless. How kind to share your knowledge and you have a gift for clear instructions.
I could not help but reply to you if only to tell you we share the same name apart from one letter!! Clearly we also share a common problem with patterns!
Thank you so much, I’m glad to be of help!
I just came across this site & I want to say thanks for the great information. I have a question. Once adjustments are made to the front, nothing needs to be done to the back piece, as far as hems & side seams to match the front?
Hi Dawn, you should check the length of the side seam of the front with the back. lengthen the back if necessary. I’ve changed this in the tutorial, thanks!
How about for a knit dress with a gathered bodice? I’m making my granddaughter her prom dress and she choose on that has light gathering under the bust, but it is definitely based on a B cup. She is a D. Just add length?
Hi Pamela, I’d do a real FBA. The gathering under the bust is the same as if there would be a dart, rotated from the side to the bottom.
Thanks for a very clear explanation.
Does this adjustment also accommodate for protruding tummy/ pregnant belly? Do I need to lengthen the front and curve too to cover the belly? Thanks.
Hi Meike, no it doesn’t, but you could skip step 7 where you redraft the side seam. That way you keep the extra room around the belly. And I would also lengthen the front, you can curve the front hem line down and keep the side seams the same length as the back, for instance.
Hello! I am so happy to have found this! I have the Grainline Tamarack jacket pattern. I will definitely need to do an FBA, and I have held off making my muslin because I couldn’t figure out how to do it without ruining the lines of the jacket. I am so grateful for this, you have no idea.
I’m glad to hear that! Have fun with the Tamarack!
thank you, your drawings and explanation are outstanding.
I have a question about the dart that was added. If you don’t proceed through the steps to remove the dart, do you have to then sew the dart?
Hi Kristen, yes, in that case you’ll have to sew the dart.
After cutting the green, red and blue lines how do I get the pattern to lay flat?
Hi Donna, you shift the pieces in a way that they will lie flat. If it does not, maybe you’ve missed a step? Remember to also cut into the seam allowance of the green line, so you can pivot at the sewing line and not at the armhole edge.
Best instruction for FBA l have come across. If you want to put the dart for a less boxy look,do you still take the amount out off the side seam as with no dart instruction. Thank you.
Thank you! And no, in that case you leave the side seam as is.
I have a difference of 4 inches between high bust and full bust. I’ve made a FBA to one pattern and after making it up in muslin I found there was almost an inch too much fabric at center front (between two apex points) Since the pattern is cut on the fold, I moved the center line over 1/2 inch and redrew the neckline to have the same shape as the original pattern. The fit was much improved and darts took care of the FBA. Why would this extra width result at center front? Is it by making too big gap in the FBA? I added 1″ at the green line. Thanks for great instructions!
Hi Beverly, could it be that you have put the apex too far out towards the side seam, or maybe you have added more width in the FBA than you needed?
Hi, great tutorial, my one question is how do I know how much space I need to adjust between all my cut pieces? Thanks
Hi Bekah, this is explained in this post: Princess Seam Full Bust Adjustment Pt. 1
Thanks for the great instructions! I’m sewing a longsleeve shirt for my friend who needs an FBA. When I redraft the dart, how do I know how far I have to move it away from the apex? It says 1-2 inches. Does it depend also on how much I had to add? My friend needed 5.5inches total, so I added 2.75in on the pattern, but now I don’t know if it will be okay if I just move the dart 1inch away from the apex or should it just go to the green line on the right side like in the illustration.
Thanks a lot in advance!
Hi Lena, I assume you want to re-draft the dart and then sew it, instead of drafting it out? If not the armhole gets too distorted. 1-2 inches depends on the amount you added. In your case I would go with 1.5 inch and then see how it looks on her. If it seems to make a point at her bust, move it further out, 1.75 inch for instance. You can also curve the dart a bit, so both the dart legs curve inward, that makes a more rounded dart in the fabric and a less pointy end.
Thank you so much for this clear explanation and illustrations. And I wondered why RTW never fit me!
RTW hardly fits anyone! Hurray for sewing :)
I am so pleased I found this. At last an easy to understand tutorial for something I’ve been struggling with. Thank you so much.
Glad it was of help!
I need to do a 3.5″ FBA. I have used this method and several others but I am always left with the armhole being too short. When I move the green line 1 3/4″ it moves the armhole up about one inch. When I make up the garment the arms are too tight and pull at my underarm. Am I doing something wrong? Or, what do I do to correct this. I am doing a garment for knit fabric.
Hi Barbara, you can experiment and try to re-trace the original armhole onto the pattern after the FBA. This will shave off the raised bit.
Really love this. One question, when drawing the red line from the apex to the side seam, where on the side seam should you be aiming for? Thanks
About 2 inches below the armhole, but it depends a bit – aim for the same height as the fullest part of your bust.
Thank you for your wonderful explanation and illustrations. Great job. Great help.
Hi! Love this tutorial – thank you! I’m not clear on how to do the elimination of the dart – there seems to be repetition of the text in steps 6 & 7?
Hi Mel, yes something was going wrong in the backend, sorry about this! I’ve fixed it now.
I have a really simple question. I’m not clear on what size cup you draft for? If you draft for a B, I need a FBA, if you draft for a C, I don’t. I’m planning to buy the Onyx Bundle because I love the boxy, dart less look. My measurements are HB 32.5”, Bust 36”, Waist 29” and Hip 38.5”. Looking at the size chart, I seem to fit a size 4 perfectly, but I’m afraid it’ll be too big in the shoulders, neck, etc. can you help me out? Thanks.
Hi Paula, the lower part of the size range is drafted in an A/B, the upper in a C/D. So for size 4 I would do an FBA, especially because the Onyx is a woven shirt.