How to Make a Bra – part 1, drafting the pattern

One of the most satisfying and useful things to be able to make yourself is a bra. This is especially true if you take a larger or ‘awkward’ size, and have trouble finding attractive and well-fitting bras in the shops. This week, I’ll be showing you how to sew a bra from scratch at home. Today, I’ll be showing you one way to draft your own custom-fit bra pattern.

The traditional way of making a 100% custom-fit bra pattern is to drape the breast, by supporting it with tape or a ‘sling’ of ribbon, and then taping or pinning fabric over it to form the cup pattern. This is a very useful technique, but I soon found that, nature having been generous, that it was incredibly difficult to tape myself into position without squishing myself all out of shape! This would have resulted in some rather unusually shaped cups, so an alternative was in order.

For this method you’ll need:

  • paper and pencil
  • tape measure
  • underwires for your size – you can either purchase these from a specialist supplier, or salvage some from an old bra
  • ruler
  • protractor
  • scissors

First, we’ll draft the cup pattern. Our basic cup shape is going to be a three-part cup, a hemisphere with a slice taken out of the top, as this is both comfortable and aesthetically pleasing. If you prefer a different silhouette, you can of course tweak the pattern at the fitting stage (covered on Wednesday).

The main pattern piece we need to make is a rounded-out triangle. To get the length of the sides, we need two measurements – the circumference of the underwire, and the circumference of the breast. Measure your underwire diameter as shown, ignoring the ‘tail’. Multiply this number by pi to get the circumference, then divide in four to get the quarter-circumference. For example, my wire diameter is 16cm.

Circumference=16 x 3.14=50.24

Quarter-circumference= 50.24/2=12.56cm

To get the circumference of your breast, hold or tape the underwire in position against your chest, and measure across your breast, at it’s fullest point, from one side of the underwire to the other. I get 27cm, so the quarter-circumference is 13.5cm.

The corners of our rounded-triangle need to be 90°. To make the lines curve the right way, we could do some complex calculations and fiddle around with compasses, but the easiest way is actually to split the line into 4 and put an angle of 10° between each section of the line.

So, to make the longer sides of my triangle, I’ll divide the breast quarter-circumference by 4, giving 13.5/4=3.4cm (rounded up).

I start by drawing 2 lines 3.4cm long at right-angles to each other. Then add another line, 3.4cm long, at 10° to the first, and another, 10° to the second, and another, at 10° to the third. The corner will, of course, be a right-angle, with the third side drawn in the same way (but based on the underwire measurement). You should be able to see what I mean from the picture above.

You now have your basic triangle, with the sides curved so that when joined together, they will form a hemisphere. Cut out 4 of these. Two will form the lower part of the cup. To make the top section of the cup, tape two of your triangles together as shown, and cut off the top 2/3, following the curve of the lower edge.

You now have a basic cup block, which on Wednesday we will turn into a full pattern. Many women find that their breasts are slightly different sizes, and if this is very much the case, you may wish to make a pattern for each cup.

Lets have a look at the band block. This is actually the most important part of the bra, as the band is supposed to do most of the support work. You can actually apply pretty much any cup to a correctly fitting band and have a good bra, so take your time measuring and drafting the band and you’ll be able to use it over and over.

Begin by cutting a rectangle, the same length as your underbust measurement, and slightly deeper than the underwire. Divide the rectangle into quarters – this marks the centre front, and the side seams.

Place your underwires at either side of the centre front, with their centres about 20cm apart (you can increase or decrease this if you have a wide or narrow torso). Trace the wires, and mark their centre point. Mark an additional line about 1/3 across the back from the side-seam line.

As rib-cages are not tubes, but increase in circumference as you go up, we are going to add some shaping to the bra-band so that it hugs the ribcage securely. To do this, we’ll add a spread of around 34°, in total.

Cut your rectangle at the side seam, third-back-line, and at the centre points of the underwire, and lay the pieces out on another piece of paper. Trace the centre section, then place the side pieces at 5°, so you are adding a 5° spread to the centre line of the underwire. Trace around these sections, then add 8° at the side-seams. Finally, add 4° at the third-back line.

Trace the underwires onto your new pattern block, and mark a line straight across at the centre top end of the wires.

You can now shape your curved rectangle as desired along the top edge, to make your completed band pattern block.

We now have the basic outline of our bra pattern. On Wednesday, we’ll be fitting and styling the pieces in order to make a finished pattern :)

15 thoughts on “How to Make a Bra – part 1, drafting the pattern

  1. Ok, I’m lost. The paragraph that starts “I start by drawing 2 lines 3.4cm long at right-angles to each other”: I think I’m missing a reference point. Could you take a picture combining pictures 4 and 6, so that you have the pieces laid out like #6, but with all the lines drawn like #4, and scales pointing at which measurement is which? I’m guessing that the outer and middle sides are 12.56, while the uppers are 13.5, but I can’t find how you are using the 10 degrees.

    Oh wait! Ok. So you draw a line that is 3.4 (1/16 circ), turn 10degs, continue another 3.4, turn, continue, totaling 13.5 and having curved 30 degs total. Then you take a 90deg turn and do the same, and another one, but now with 3.14.

    Ok, I understand it all, but the pictures aren’t very distinguishable. I’d recommend tracing everything with a heavy black line, so that the pieces don’t blur together.

  2. Okay….seriously. I think you missed your calling. You should have been an engineer of some sort.
    You could probably build a bridge, if you had to. Making a good bra can’t be anymore challenging then spanning a river.

    Awesome tutorial. but I know WAY better than to try this at home.:)
    K

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  5. thanks for the great tutorial…just pointing out a small typo Quarter-circumference= 50.24/2=12.56cm should be 50.24/4

  6. Im lost at the part about the under bust measurement…is it the measurement right around your body or just under ur breasts from left to right?

  7. I’m stuck doing the band. It looks as though you are cutting the rectangle to cut out where the cups sit. Is this rectangle only going to the end of the cup? How are you figuring the length of the band? What measurements are you using? Are you using half the band measurement around the rib cage to center front? I’m hoping you can clarify this.
    Thank you!

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