7/30/2019 How to Calculate Your Bust Dart Size

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The Sewing Corner

"How to Calculate Your Bust Dart Size: The Formula that Takesthe Guess-work out of FBAs and SBAs"When you look in Pattern-making books they usually have a table of standard measurements

including either the bust dart width, or it's angle in degrees. These "standard measurements" are for a

B-cup, which means that if you are nota B-cup, you have to draft the pattern and then do either aSmall Bust Adjustment or a Full Bust Adjustment.

But how do they get these numbers? They seem to have nothing to do with the rest of themeasurements. But there is always a formula. It just takes a bit of working out.

What is a bust dart's function? As I see it, a bust dart is there to make the longer front pattern piece

match the shorter back pattern piece at the side seam. The front pattern piece is longer than the backone because it has your bust to go over and the back doesn't.

So to find out the bust dart's width at the side seem,

1. you measure your front from the neck point (N) over the apex, and thence straight down toyour waistline = F;

2. then measure from N down your back to your waistline = B;3. subtract B from F and you have your bust dart width.

Now for a little trigonometry. Scientific calculators at the ready!

We'll split the bust dart into two equal parts so that we have two right angle triangles:

The difference between my front measurement and my back measurement is about 2 cm (halved to 1

cm for the split triangle), and the side dart length is about 13 cm.

How to Find Your Bust Dart Angle for Patternmaking in FashionIf you are using the German method of pattern making, which is briefly taught inPatternmaking in

Fashionby Lucia Mors de Castro (mine cost about 40 but it now costs 100 at Amazon due to high

demand - I think it is over-priced now by very greedy sellers), you will need the angle of the bustdart, and as we have the length of the dart (the hypotenuse) and the width of the dart (the length

"opposite" the angle) we can find the Sine of the angle (sin = O/h) and then use the sin-1 function onour scientific calculators to find the angle. Thus:-

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7/30/2019 How to Calculate Your Bust Dart Size

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How to Find Your Bust Dart Width for Metric Pattern CuttingIf you are usingMetric Pattern Cutting for Women's Wearby Winifred Aldrich, or the instructions

onwww.BurdaStyle.com, you will want to find the bust dart width for a shoulder dart.

1. Take the sine you found earlier (here 0.077) and multiply it by your neck to apexmeasurement (on me about 24 cm) to get halfyour total bust dart width. (Here, about 1.84cm).

2. Get your total bust dart width by doubling this number = 3.68 cm, roughly 3.7 cm.

So that is my bust dart: 3.7 cm wide at the neck point and 8.8 degrees (which can be rounded to 9

degrees for practical reasons).

So that is how you work out your personal bust dart measurement. Isn't it so much better than using a"standard" measurement?

I hope it helps. : )

Sabrina

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