All About Power Bars (II): Drafting & Sewing an Internal Power Bar

Hi there! If you remember the first post of this series,  you already know what power bars are and why do we use them. In the next posts we’re going to see how to draft and sew the different types of power bars, using a basic bra pattern as our basis. Today’s post will cover the drafting, cutting and sewing of the internal power bar. Let’s begin! 😉

Drafting the Internal power bar

This type of power bar is the easiest to draft: simply, draw a straight line from the strap attachment on your bra pattern, down to the lower cup of the bra. It could end almost wherever you want, but it should not go past the notch that is usually below the apex of the bra (See the images below).


If you’re working with a vertical seam pattern, this is really straightforward, but if your bra pattern has an horizontal or diagonal seamed cup, you’ll need to do some extra work: first, mark the seamlines on  both the upper and lower cup pattern pieces (some patterns have the seamlines already marked on the pattern pieces. If that’s not the case and you know that the seam allowance of your pattern is, let’s say, ¼ inches, draw a line at ¼ inches from the edge of your pattern, parallel to that edge. That’s your seamline!). Mark as well the apex of the cup (usually it’s already marked by a notch. If not, you can identify it easily as the highest point of the curve in the lower cup). Measure the distance between the apex and the underarm edge and make another mark at the halfway point.

Power bar draftig Step 1 - Mark seamlines Now, overlap the pattern pieces at the underarm edge by the amount of the seam allowance, so the seamlines are one on top of each other. Match the seamlines more or less until you reach the mark that was halfway between the underarm and the apex. Then, with the help of a ruler, draw a straight line from the strap attachment down to the lower edge of the bra. This line should pass near the mark at the halfway point, and it shouldn’t end past the apex of the bra.

Power bar drafting step2

And… Ta-dah! You’ve got your power bar! Trace the pattern on a separate sheet of paper and you’re ready to cut it and sew it to your bra!

Cutting the internal power bar

Before you cut your internal power bar, you’ll need to know where are the DoGS (Direction of Greatest Stretch) on this pattern. So, to mark the DoGS you just have to draw a line parallel to the strap attachment. Easy, right? 🙂

Now, what fabric do you use for your power bar? You can the same fabric that you used for the cup of the bra, or you can also use sheer cup lining or 15denier fabric. In any case, the fabric shouldn’t be thick, and it shouldn’t have any stretch lengthwise, but it could have a bit of give crosswise.

Internal Power bar drafting step3You can also cut the power bar on the fold, so you don’t have to worry about finishing the straight edge: cutting it on the fold allows you to have a clean, smooth edge (that’s what I did on this bra, and I’ve seen it done in several RTW bras).

Sewing the internal power bar

You need all your bra cup pieces sewn together before sewing the power bar. Then, the only thing left to do is sewing the power bar to the finished cup along the curved edge (on the wrong side of the cup, of course!). Once you have it, you carry on with the bra construction as usual 😉

Internal power bar sewing

And last but not least…

Some examples of the internal power bar! (you can see some more on the first post of this series). See you next week!!

MYLA – Heritage Lace Non Padded Balcony – Image via Journelle


GOSSARD – Superboost Lace Foil Print Plunge Bra – Image via Gossard


CALVIN KLEIN – Black Sling Balconette Bra – Image via Urban Outfitters


  1. Sofía, you are a doll! Thank you so much for this description, it’s very clear, and to be honest, I haven’t read any tutorial on powerbars yet! I’m gonna definitely try it out, I love the Calvin Klein version. Maybe I make like that one but opposite – lace powerbar and tulle fabric.
    I’m very inspired!

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