Today is the second post in a 2 part series on doing full bust adjustments on patterns without any darts. For the first post, we covered a quick and dirty ‘pivot and slide’ method that works well for small full bust adjustments. Today, we will be covering how to do a proper slash and spread full bust adjustment, even when the pattern does not have any darts.
This post is part of a sewalong for the Blackwood Cardigan. You can grab your copy of the Blackwood here.
Do you need a full bust adjustment? The first thing we need to do is measure our high bust and our full bust. To measure the high bust, place the tape around your back, under your armpits, and across your chest ABOVE your breasts. To get your full bust, measure your bust across the fullest part of your chest.
Next, find the bust measurement of the pattern you are working with. Choose your size based on your high bust measurement and do the following calculation:
Your full bust measurement minus the pattern bust measurement.
If the difference between the two measurements is more than 2”, you are a good candidate for a full bust adjustment (FBA). The process can seem daunting, but trust me, learning how to do a FBA can be a total game changer for your sewing practice. You will be amazed at how much better things fit!
Let’s get started!
Start by tracing your pattern piece onto a new sheet of paper. You want to keep the original pattern piece intact. You will need extra paper to fill in the gaps as we cut into our pattern for the FBA. Keep paper, pens, a ruler, and tape handy for this exercise.
Hold the pattern piece up to your body as close as you can to where it will sit when worn and mark where the ‘apex’ is (it’s right where your nipple is). Don’t fret about being 100% accurate, just eyeball it.
Draw three lines. #1 from the apex to the side seam, roughly where a bust dart would be if there was one. #2 from the armscye to the apex and then straight down to the bottom, perpendicular to the bottom edge. #3 out to the front edge or center front fold line (depending on the type of pattern you are working with). The #3 line should be perpendicular to the #2 line and be about 2-4″ up from the bottom edge. Again, just eyeball this to look like the picture below.
Cut line #2 from the bottom, stopping 3/8″ from the edge (or however much the seam allowance is on your pattern). This is indicated by the black dot in the diagram below. You may need to cut into the seam allowance from the edge to get a smooth pivot point here, or you can simply create a small fold. Cut line #1, leaving a small bit of paper intact where line #1 meets line #2 if possible (again, this is for pivoting). Completely cut through line #3. This is called ‘slashing’. Now, ‘spread’ the pieces out as in the diagram below.
You want to focus your attention on the width of the gap in line #2. This width should be half of the difference between your full bust measurement and the pattern bust measurement.
For example, if I have a difference of 3”, I divide that by 2 to get 1.5”. The gap in #2 should measure 1.5″ for me.
Place paper under your pattern piece and measure the gap before securing it in place. the two sides of line #2 should always be parallel. Once taped down, your new dart will fall into place and you can move the little piece from slashing line #3 down to true up the bottom edge of the pattern. Tape these all down onto more paper, filling in the gaps. Trim of excess paper.
Now you have a dart-like shape, but it is not pointing at the right spot. It needs to be re-drawn to point to the apex. Using a pen and ruler, re-draw the dart to point at the apex mark (shown as line #4 in teal below).
OK! We have a pretty great start here, but you are probably wondering – why do we have a dart? Isn’t the whole point to not have any darts? Well, that depends. Darts can help get a great fit through the bust. They might be uncommon in RTW knit garments, that that doesn’t mean you can’t have them! If you want to keep the dart, all you need to do is ‘back off’ the dart point 1-2″ from the apex. You also need to add a dart hat. If you want to get rid of the dart, skip down to the next step.
If making the Blackwood Cardigan, you should adjust the front and bottom band. Add the same amount of length to the front band as you did to the front of the bodice. Add the same amount of width to the bottom band as you did to the bottom of the bodice.
We had to create the dart in order to make the adjustment, and now we are going to redistribute the excess fabric in that dart in order to eliminate it.
Slash open your new dart by cutting it out completely or cutting one edge so you can rotate it.
Cut along the inner side of the original #2 line to the apex mark. Try to leave a little paper for pivoting here. Rotate the side piece out to close the dart. Tape it shut. Buh-bye dart!
Fill in the new gap with paper and leave some extra paper on the side for the next steps.
Now we have a huge waist dart. We need to get rid of this. Using the gap in the dart as a guide, draw a new dart with the point near the bottom of the armscye. Slash open the left leg, leaving a bit of paper.
Close the dart by swinging the lower right portion of the pattern over. Tape closed.
Blend down from the side seam to the hem.
If you are making the Blackwood Cardigan, you should adjust the front band. Add the same amount of length to the front band as you did to the front of the bodice.
See? That wasn’t too complicated, was it? I know it is a lot of paper and cutting and lines and what not, but once you do one, you will love the results. Soon, FBA’s will be second nature to you!
Remember to also check out the ‘pivot and slide’ FBA method as well. You may find that is all you need!
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37 Comments on “How to do a full bust adjustment without any darts”
Thank you for your two part tutorial!! I have been recently scouring Pinterest and Google for these very adjustments. While a found a few that are similar, you have explained these two techniques more clearly and concisely than any that I was able to find by far! This will be very helpful to me and I’ll be referring back on a regular basis.
Excellent post for the bigger busted. Thank you very much. I wrote a post recently on how to do a FBA on a wrap top (Gertie for Butterick B6285) here http://plumage.me.uk/2017/03/full-bust-adjustment-on-wrap-top-butterick-b6285-by-gertie/ which hopefully is also helpful!
Thanks, Deborah! I love how many awesome resources are out there now, this is awesome 🙂
I think I finally understand FBA’s.
I have read other blog posts, but your diagrams and explanations are great. Thanks for this excellent reference.
Thank you Asheley! That is really nice to hear 🙂
You have the best graphics. I did an FBA this same way on my Greenwood tanks and it worked perfectly. Definitely worth the extra effort. 😉
I am just wondering, you mention since you have a 3″ difference, you split that by 2″ to get 1.5″. However, doesn’t the pattern already include a 2″ difference, so why is it not 3″-2″ = 1″ and divide the 1″ in half, to get a gap of 0.5″ per side?? My other question is, do you work with the pattern piece from your over bust size? (so overbust plus 2″ to find full bust piece to alter). Any help is appreciated 🙂 Trying to fully understand FBAs…
I have the same question as Kristen – wouldn’t you subtract out the 2″ difference already accounted for, then divide the difference in half? Thanks! This is a great tutorial!!!
Hi Helen.
Your post was the best I have come across, so I don’t suppose you would be able to do one on a princess line dress would you? PLEEEEEEASE! XXX
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My difference is exactly 2” so which method do I use?
I would try the quick method first!
I must be doing something wrong, but when I compare my new pattern piece with the FBA, it’s exactly the same width across at the bust as the old pattern! I am assuming it’s something with the cutting and then folding on top over… I assume that is not the intended outcome?
Same here. Only the bottom hem got wider.
Same here. The only place I got the intended 3/4 inch is the waist.
I am sewing V1415, the front is all one piece. I’m assuming I just do the same thing on both sides?
Yep, exactly!
Thanks for this! I wear an M cup (J in UK) and wanted to try this, as my measurements always align to 2-3 different sizes & the bust/shoulders often don’t fit quite right.
nicely explained. thank you.
Oh my goodness thank you for this! My pattern adjustment book doesn’t detail the last step and that makes a BIG difference! The button down pattern I’m specifically working on isn’t swimming around my hips anymore. Y’all are the best. Cheers for, as always, well written and well illustrated adjustment instructions.
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Yayyyyy! I have finally properly managed FBAs, but I hate putting darts in simple knit garments! This is life changing for me, and your instructions are SO GOOD! Thank you!!
Thank you, this is exactly what I needed! I also need to adjust to add length, I assume I should do length before bust, is that right?
Yes, lengthen the pattern first and then do the FBA. You can do it the other way too, but I would lengthen first, personally.
Thank you for this very clear tutorial. I always need to do some kind of FBA to get a better fit. This winter I am planning on making a raincoat that does not have darts ( nor should it) or princess seams so I am going to try this technique on the front pieces so I can get a better fit. You are a wonderful resource to the sewing community.
I think this post is in error. I am a person with very large bust to upper chest ratio so I have to do an FBA always. I formerly praised this post but the extra fullness that is in the front or the side has to be there as you need more room. It can be rotated around but you can’t get rid of it because then you are back at the beginning…. it has to go somewhere . I have made several dartless FBAs and it usually means there is an additional pie shaped piece On the bottom or a boob bump on the side that needs easing in. I am not an expert but I think this is misinformation.
Hi Linda,
Thanks for your thoughts on this tutorial. This method results in additional width under the arm and additional length in the front. It is best suited for knit garments. I have also used the method where you have a boob bump on the side and I like that one too. You could incorporate that into this method for even more added room. This method does add room but as you said, there are lots of methods, it is always good to use the ones that work for you!
I was wondering what a dart hat was and then I went to the next stage and there it was! Great instructions. I feel that I am able to do this adjustment now.
My pattern (Reynolds) has a dart. Does this work FBA work for that too?
Hi Suzanne,
I recommend using a tutorial designed for an FBA darted pattern. The process is quite similar, but it will be easier to follow along on one with a dart.
Thank you for this detailed tutorial (though I’m afraid it still looks pretty complicated to me!). I’m about to try a woven top pattern with no darts – would this method work? It looks likes it’s designed mainly for knits. My high-to-full bust difference is about 2.5″, for this pattern.
Hi Sophie! We have another post about this adjustment on a woven pattern that might be more helpful: https://helensclosetpatterns.com/2021/04/13/full-bust-adjustment-dartless-bodice/
Thank you so much for this tutorial. I have a 7″ difference in high bust and full bust. (All naturally grown). Most tutorials skip the dart hat and go straight to closing the dart and widening the from. I personally think my clothes look better WITH a dart and not all baggy (swing style) at the waist. With such a large bust, adding the extra I need to the waist only makes the garment stick out from my body and make me look pregnant. AT 58 that is not a good look. 🙂 I would love a tutorial for a FBA in a princess seam top.
Thank you for dispelling the myth of the full bust adjustment. I was dreading the process!
Hey , im so stuck with this :-s for me the gap in line 2 should be 2 inches but if i do this is completely realigns the armhole so much that the sleeve piece wouldnt fit. I tried out a 1.5 inch difference and doing so leaves the armhole the same shape but increasing above this changes it…any insight?? Thank you in advance
Hi Linzi,
It sounds like a 2″ gap might be too big for this style of adjustment. You may need to consider adding a dart to the pattern, or doing a smaller 1.5″ adjustment and adding some additionalextra width by curving out the side seam at the bust. You could try this method here: https://blog.cashmerette.com/2020/10/how-to-do-a-knit-fba.html