Over the last two weeks, I’ve posted the tutorials and patterns for the Seashell Bikini. This week, we’re learning how to hand sew the elastic band onto the bikini bottom. 

You may ask yourself why you would want to add some elastic to the bikini bottom if we are already making it in your size? Short answer: it will fit even better

Yes the bikini bottom should have ended up in your size and fit your bottom fabulously, but a little elastic goes a long way in making this garment hug your curves and really bring out your shape. It will fit more snuggly up against your skin, which not only makes the piece look better, but it will keep the bottom from sagging when the fabric gets wet. Remember that we are using a cotton blend yarn, and not a super thin and stretchy material to make the bikini, so when the fabric gets wet, it will sag a little. And really, who wants a saggy bikini bottom?

Also, swimming. I don’t know about you, but if I am wearing a bikini, it means I’m hitting the water and swimming. Adding the elastic to the bikini bottom keeps the fabric tight against your skin. Which means that you can swim and move around in the water, without worrying about any skin peeking through. 

Really, it is just an option and whether you choose to add it or not, the biki will look and fit beautifully either way. 

How do we sew this thing on? 

First, lay your fabric on a flat surface and measure out how much elastic you will need.

Measure from the front of the gusset (closest to the front of the panty), and along the sides to the back waistband.  

Decide how tight you want the bikini bottom to fit, then cut the elastic according to your preference. For instance:

If you want the fabric to fit you just a little tight, (about as tightly as a store-bought bikini would fit), cut the elastic about ¾ of the length between the front gusset and the waistband. 

I would suggest most folks use this measurement. It adds enough stretch to the elastic to make the fabric fit comfortably. For those of you that want a super-tight fit, use the measurement below. 

For a really tight fit, cut the elastic about ½ the length between the front gusset and the back waistband. This is the measurement I used in the tutorial, but know that it makes the bottom fit really, very tightly. 

Next, place the narrow end of the elastic on the inside of the bikini bottom, where the front of the gusset starts. Sew across the top of the narrow side of the elastic 2-3 times.


Once the narrow end of the elastic is securely sewn onto the fabric, hold the stitches down to keep the fabric from tearing when you pull on the elastic, and sew along the length of the elastic, securing it to the fabric. 

You will need to pull on the elastic as you sew it along the fabric, in order to stretch it out along the length of the inside of the leg and towards the back waistband. 

The easiest way to do this, is to sit cross-legged and use your legs to hold the elastic taut while you sew it onto the fabric. I normally pinch the elastic with the fold behind the knee, or pinch it between my shins to hold the elastic in place. It sounds weird, I know, but it really works. Plus, it keeps your hands from cramping, which they will if you have to hold the fabric, pull the elastic, and sew it all simultaneously. 

Once you finish sewing along the sides, sew across the narrow end of the elastic 2-3 times. Repeat on the other side of the bikini bottom. 

For a step-by-step explanation, you can watch the tutorial:

Written by

Atenas Ruiz-Ramos

Hi there!

I’m Atenas, the designer and content creator for Mode Bespoke.

When I’m not designing patterns or creating tutorials for YouTube, I spend my time making things, reading, writing, or learning something new.

I’m a linguist, musician, martial artist, seamstress, fantasy & sci-fi novelist, bibliophile, artist, cooking enthusiast, soap maker, budding mechanic, gardener, and a mom.