The Triangle Bikini Top

The world's most popular ever bikini top has changed little in 40 years. It is so popular it suits young and not so young, large and small busts, and can be worn with any style of bottoms you want. Thanks to the strings you don't really need to care about size or cup. If one size doesn't fit you just keep going up or down a size until something does fit. And if that isn't enough, these days you can mix and match at most swimwear outlets so not ony can you have different size tops and bottoms, but also different colours. Some retailers even sell tops and bottoms separately so you don't even need to buy a bottom at the same time. Heck even I'm excited by such choice.

There are two main configurations of the triangle top. The first is a triangular section with a dart used to create the cup shape. The second is a wider triangular section that depends an a draw string to gather the triangle into a cup shape. The first is a flatter sitting garment, while the second is bulky but adjusts to fit almost any cup size. The draw string is popular with suf wear brands, while the darted version is typically produced by more fashionable labels. There is of course quite an overlap.

The sketch above illustrates the pattern we're going to make. We will then also show the extra steps to create a draw string triangle top. These patterns are for a size 10B/C and are not based on the one piece block but on measurements. Before you start each step, click on the link marked "Illustration for this Step". A pop up window with an illustration for that step will help guide you through the instructions. At the end of each step your draft should match the illustration.

Step One

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Mark a point in the center of your page. Square up 10cm. Square left 7cm. Square right 7cm. Square down 7cm. Create two lines 15° either side of the bottom guide line.

Step Two

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Square down 7cm from the end of each horizontal guide line and square between them. This should form two 7cm by 7cm squares.

Step Three

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Rotate the squares about the center point until they line up with the 15° guide lines.

Step Four

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Curve off the left and right of your triangle. These curves should be as slight as possible, being sure to keep a right angle at the bottom.

Step Five

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Bring the tip of the dart about 1.5cm down fom the center point (bust point). Do not take it further away than this or the tip will pimple when worn.

Step Six

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Remove the guidelines, if necessary retrace the panel. Be sure to clearly label your pattern with a title, panel name, size, cutting instructions, author’s name, date and revision number. Finaly, add seam allowance to the pattern based on how you intend to assemble it. I've shown this pattern with 10mm allowance for overlocked seams (8mm to blade, 2mm off cut) at the dart only. I would use bound elastic for this piece which does not require seam allowance.

Step Seven

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In order to create a gathered triangle with a draw string, we need to add a little volume. We still want the same final shape so we can base our gathered triangle on the darted triangle. Trace the darted triangle and open it up as shown, a total of about 30°.

Step Eight

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Curve off the base of your triangle. This curve should also be as slight as possible, being sure to keep a right angle at either side.

Step Nine

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Retrace the panel. Be sure to clearly label your pattern with a title, panel name, size, cutting instructions, author’s name, date and revision number. Finaly, add seam allowance to the pattern based on how you intend to assemble it. I've shown this pattern with 20mm allowance for a fold over casing with overlocked edge. Most industry would simply straight stitch the casing down from the inside assuming it doesn't need to stretch. I prefer to chain stitch from the outside because I'm not in such a hurry. I would use bound elastic for the sides of this piece which does not require seam allowance.