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5 Out of 4 Patterns Ultimate Bikini Turned Ultimate Underwear Tutorial

I recently had the pleasure of working with Jessica from 5 Out of 4 Patterns, testing her newest pattern releases.

She designed two great new pieces that work well together as a swimsuit, and they also coordinate well with the other patterns on her site.

I was really excited to test drive a swimsuit pattern. Since I have been sewing more of my own clothing, I have been learning a lot about why ready-to-wear (rtw) clothing doesn’t quite fit me right and what to do about it.

My excitement was soon squashed, as I found out tIMG_2172hat the swimsuit material that our local fabric store sells isn’t really suitable for swimsuits. It is a 2 way stretch, and you look at any good rtw swimsuit, the fabric has a nice weight to it and is a 4 way stretch.

I was trying to figure out how I was going to make this work. I decided to do up a muslin of the top in a cotton/lycra that I had in my stash. I did the straight tankini and quickly realized that this makes a great summer tank top.

That led me to figure out what I could do with the bottoms. I figured I may as well try them out in the same cotton/lycra and they would probably make some decent underwear. I mashed it up by taking some of ideas off of some rtw underwear and incorporating it into the swimsuit pattern.

And that led to a couple of other adaptations and now I can whip up a pair of undies in less time that it would take to do laundry!

First off, you will need to grab your own copy of the Ultimate Bikini Bottoms. And if you want to make a matching sports bra or tank, grab the X-Factor Bikini and Tankini Top. Both of these patterns have so many options that you will never get bored. And did I mention that it is maternity and nursing friendly!!!

The Ultimate Underwear Tutorial

The first things you will need to do is to gather your supplies and print your pattern pieces.

You will need to print the following pattern pieces. Page 1 is a test square. If you are new to PDF patterns, this square needs to measure EXACTLY the right size or your garment will not be true to size. It is amazing how big a difference an 1/8″ difference in your test square can make over the whole pattern. There are directions in the pdf file that tell you precisely what you need to do to print correctly.

These are the patterns pages you will need to print:

  • for up to and including medium, you will need to print pages 2 to 7
  • for large and up, you will need to print pages 2 to 8
  • you will also need to create a gusset/lining piece and so you will need to print out and extra page 2IMG_2219

Due to copyright issues, I can not show you the actual pattern pieces, but to create the gusset/lining piece, take your extra page 2 and cut out the pattern piece and the gray page guide at the bottom now becomes the front edge of the gusset/lining piece.

These are the supplies you will need:

  • approximately 1/2 meter of 4 way stretch material
  • thread
  • fold over elastic-you will have to measure your pattern pieces to determine how much for each size

You will need to cut out 1 front piece, 1 back piece and 1 gusset/lining piece.



I wasn’t thinking when picking out material for this tutorial, so I apologize in advance that this is going to be hard to see. I will try my best to make this clear as to how to IMG_2220assemble the pieces in the right way.

In the picture, the front piece is on the bottom and the right side of the fabric is facing up and the edge of the crotch is to the right.

On top of that, we have the back piece, also with the crotch piece to the right, but now the fabric is wrong side up. The front and back pieces will be right sides together.

The top piece is the gusset/lining. You will have the wrong side of the fabric facing up and make sure that the end that has the angles on the corners is on the right side. It matches the same angles as the lower two pieces. You can see the angled corner I am talking about just below the pin in the lower right of this picture. Pin this edge together, as shown.



I chose to serge this seam together but you could just as easily use a stretch stitch or zigzag stitch on your sewing machine. I just happened to have the thread colour I wanted to use in my serger but not in my sewing machine, so it was simply a matter of convenience 🙂









When you are finished and you open this up to the wrong side facing up, this is what you should see. The seam at the back of the gusset/lining is nicely enclosed. You could also serge the front edge of the gusset/lining, but since knits don’t unravel, this step isn’t necessary. I think it may be slightly more comfortable not serging it. If you chose to make these out of a stretch lace, however, you may want to consider finishing this front edge.





At this point you could finish off the leg and waist opening one of the three ways Jessica shows in her pattern, but I chose a slightly different path.

You will need to figure out how much fold over elastic you will need for each of the leg openings and the waist. FOE does not have as much stretch as other elastics so I chose to take the fold over elastic and run it along the edge of the corresponding pattern piece(the leg opening and the waist) to determine the length needed, taking off the 3/8″ seam allowance. There is negative ease built into the bottoms and I feel that is just enough give for the FOE without making it too tight. Don’t use the cut pieces of fabric to measure the lengths as they may stretch and give you an inaccurate measurement.



After cutting the length needed, start pinning the FOE to the edge of the leg opening . You will be pinning the non-fuzzy part of the FOE to the wrong side of the fabric and only pinning slightly short of the part where the elastic folds over.. The fuzzy part, in my opinion, feels nicer next to the skin. You will be sewing these to the legs openings while it is still flat, and sewing the sides up afterwards.







Now I am off to my sewing machine, which just happens to have thread the same colour as the FOE 🙂 Sew with a zigzag stitch, mine was at 2 width and 2 1/2 length. You will be doing the leg openings in this step. For the leg opening you will want to start your FOE 3/8″ in, to account for the seam allowance needed to sew up the leg opening.

I tried to aim for the centre of the one side of the foe  but this side won’t be showing so don’t be to stressed if you can’t get it straight. This is one time where I wonder if it might be worth getting a walking foot for my machine, as the fabric does like to shift around.






You will now fold the elastic over and do the same zigzag to secure both sides of the elastic and the fabric in the middle. I like to sew from the outside, as this is the part that will be showing, not that this will be visible to the public 🙂 Stitch close to the edge of the FOE.








I don’t know how I forgot to get a picture of the next step. But put on your imagination caps, and hopefully you can picture what I am describing.

You will be sewing up the sides. Again, you can either serge or use stretch stitch. Line up the sides and pin. As you are sewing, you have the choice of either having the ends of the FOE  butting up against each other, or slightly over-lapping.



Now onto the elastic on the waist. You will follow the same pinning procedure as you did on the legs. Pin the non-fuzzy part of the FOE to the wrong side of the fabric, just shy of the edge. the difference her is that you will be sewing this in the round. I chose to over-lapp the ends of the FOE slightly and then stitch using the zigzag all the way around. This is a horrible picture, but if you squint the right way, you can see the over-lapped ends of the FOE.





You can now fold the elastic over on the waist and finish off zigzagging along the inside edge of the FOE, just as you did for the leg openings. And you know have a super duper comfortable pair of undies.



I hope you enjoyed my first attempt at a sewing tutorial. If you have any questions or suggestions for other tutorials, please leave a comment below! I would love to have your feedback 🙂




***This post contains affiliate links that allow me to receive compensation which helps cover some of the expense of fabric and time spent writing this review. If  you would like to support me in my efforts, I would be most grateful if you would be willing to choose to use the affiliate links. Thank you!!!***

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