How to Modify Any Bag Pattern to Add a Hidden Zipper Pocket

In this blog post, you’ll learn how to modify your favourite bag pattern to add a hidden zipper pocket, a sleek and functional detail that keeps your essentials secure while maintaining a clean design. This is the first step in a two-part tutorial: today, we’ll focus on adjusting the pattern, and in the next post, I’ll show you exactly how to sew the pocket. Click here to check it out!

Why Add a Hidden Zipper Pocket?

I’m making myself a new tote bag! My last one has finally torn after years of daily use, and while I could have tried fixing it, I decided it was the perfect excuse to make a fresh one. If you’re wondering, I always return to my first sewing pattern – The Tote Bag (not the most original name, I know! 😆).

When I first designed this pattern, I wanted it to be simple and beginner-friendly, so it doesn’t include any pockets. But that’s exactly why I love returning to this project time and time again. It’s like a blank canvas, ready for any customisation I like to add.

If you’d like to grab a copy of the Tote Bag pattern, you can find it here ⬇️

If you’re looking for a simpler pocket option, you might prefer adding a slip pocket. Slip pockets are quick and easy to sew, making them an excellent choice for beginners or when you need an extra compartment without the fuss of a zipper. You can find a step-by-step guide on how to add a slip pocket to your bag in this blog post.

A hidden zipper pocket is a fantastic addition to any bag, offering both security and a sleek, professional finish. Unlike a standard zipper pocket, this one is cleverly concealed under a placket, which means the zipper stays out of sight—giving your bag a clean, polished look.

One of the best things about this pocket design is that you can use any zipper colour you like without worrying about it matching your fabric. Since the zipper is hidden, it won’t affect the overall look of your bag, making it a stress-free and stylish way to add extra storage.

This pocket is perfect for keeping small essentials safe—think keys, cards, or a phone—while maintaining the streamlined aesthetic of your bag. Whether you’re making a tote, a crossbody, or even a backpack, this pattern hack will take your sewing projects to the next level!

What You’ll Need to Modify Your Bag Pattern

Before we begin modifying your favourite bag pattern to add a hidden zipper pocket, let’s make sure you have all the necessary tools. Here’s what you’ll need:

• A pencil or pen to mark the pocket placement and trace your new pattern pieces.
• A ruler to help you measure and draw precise lines for the zipper pocket.
• Paper scissors to carefully cut your pattern pieces.
• Pattern paper or any paper you use to trace your original bag pattern.
• Your favourite bag pattern that you want to modify (specifically, the main piece, like the front or back panel of the bag).

Now that you have your supplies ready, let’s jump into the pattern modification and add that sleek hidden zipper pocket to your bag!

Pattern Modification: Adding a Hidden Zipper Pocket to Any Bag

Step 1: Determining the Placement and Size of the Pocket Opening

Take your main pattern piece; this could be the front or back panel of your bag, depending on where you want to add your pocket.

Think about how you’ll use the pocket and what you’ll store inside. Do you want it higher up for easy access or lower down to keep items more discreet?

Once you’ve decided on the ideal place, draw a horizontal line where the top edge of the pocket opening will be. This will be your guide for the next steps, so make sure it’s positioned exactly where you want the zipper to sit.

To determine the height of the pocket opening (the visible portion of the zipper), decide which zipper you’ll use and what seam allowance you’ll sew it with. This is very important because it will determine the final size of the pocket opening and help you create a precise pattern piece.

Take your zipper and measure the width of the zipper tape from edge to edge. Then, subtract twice the seam allowance (since you’ll sew on both sides of the zipper). The number you’re left with will be the final height of the pocket opening.

For example, if you’re using a #5 zipper, where the zipper tape is 3.2 cm (1 1/4″) wide, and your seam allowance is 5 mm (1/4″) on each side, the calculation would be:

3.2 cm – 5 mm – 5 mm = 2.2 cm (1 1/4″ – 1/4″ – 1/4″ = 3/4″)

That means the pocket opening should be 2.2 cm (3/4″) high.

Now that you have this measurement draw a second parallel line below the first one at the correct distance. This second line will mark the bottom edge of the pocket opening.

Step 2: Adding the Placket

Next, we need to mark the placket. To make the zipper “hidden,” the placket must be slightly longer than the pocket opening. This extra length allows the fabric to cover the zipper neatly while still keeping it accessible.

I usually make the placket about 5–10 mm (1/4 “–3/8”) longer than the pocket opening. Be careful not to make it too long, as that could make it difficult to open the zipper smoothly.

Let’s make the placket 5 mm (1/4″) longer for this tutorial. Measure that distance from the bottom edge of the pocket opening and draw another parallel line below it. This new line marks the bottom edge of the placket.

Step 3: Creating the Pocket Lining

Now that our guidelines are marked, we can create individual pattern pieces for the pocket. The first piece we’ll make is the pocket lining.

Take your main panel and fold it along the first line—the top edge of the pocket opening. Then, place a piece of paper underneath and trace around all sides to create a new pattern piece. This will form the base of your pocket lining, ensuring it aligns perfectly with the pocket opening.

Remember to trace the grainline, midpoints, and any other important markings from your original pattern.

Now, you need to add seam allowance along the top edge. Since this edge is where the zipper will be sewn, it’s important to use the same seam allowance you chose in step 1.
Measure the seam allowance from the top edge and draw a parallel line above it. This new line will be the cutting line for the pocket lining, ensuring you have enough fabric to sew the zipper neatly into place.

Add a label to ensure you know what pattern piece this is in the future. You can name it ‘Pocket Lining’ or something similar so it’s easy to identify later. Since I’ve made many hacks for this pattern, I will call it ‘Hidden Zipper Pocket’.

Also, include the cutting instructions on the pattern piece. Since this piece will be cut from the lining fabric, write ‘Cut 1 from lining fabric’ to avoid any confusion when cutting your fabric.

Taking the time to label your pattern pieces properly will make your sewing process much smoother.

Now that you’ve traced and labelled your new pattern piece, it’s time to cut it out.

Depending on the shape of your pattern, it might be best to ‘true the seam’ to ensure everything lines up properly.

To check this, fold the seam allowance along the top edge under. If you have excess paper sticking out beyond the seam line, trim it down. If there’s not enough paper, simply add more to maintain the correct seam allowance.

What I like to do is cut out my pattern piece around all sides but leave a bit of extra paper along the top edge. This allows me to make adjustments much quicker, just like you can see in the photo.

Cut away any excess paper along the sides to true the seam. This ensures the pattern piece has a clean, accurate shape and the seam allowance is even on all sides.

The first pattern piece is complete, so you can place it aside for now. We’ll use it later when we need to cut the fabric to make our hidden zipper pocket, but for now, it’s ready to go.

Step 4: Creating the Pocket

Now, we can create the second pattern piece for our pocket. You’ll need to repeat the process from Step 3, but this time, to make the main pocket pattern piece, fold the original pattern along the second line—the bottom edge of the pocket opening. Then, trace around all sides to create the new pocket piece.

Remember to add the correct seam allowance along the top edge, as this is where the zipper will be stitched.

If needed, true the seam and annotate your pattern to avoid any confusion later. You can label it ‘Pocket’ or something similar, then add the cutting instructions: ‘Cut 1 from external fabric and lining fabric’.

Step 5: Creating the Top Panel (Placket)

Take your original pattern piece and fold it along the third line—the placket. Then, trace around all sides to create the pattern for the top panel (placket). Remember to transfer the grainline, midpoints, and other notches to the new pattern.

To create the placket, measure the distance between the top and bottom lines on your original pattern. Then, take that measurement and draw a parallel line below the bottom edge of your new pattern.

Alternatively, you can simply move the original pattern and align the top line with the bottom edge of the new pattern. Once aligned, mark where the placket line is. This will ensure that the placket is the correct size.

Next, add seam allowance along the bottom edge of the placket. Since this is where the zipper will be stitched, make sure to add the same seam allowance you decided on earlier. For this example, I’ll add 5 mm (1/4″) to the bottom edge.

To true the seam, fold the extra bit you added for the placket under.

If there is any excess paper sticking out beyond the side edges, trim it off. If there is not enough paper, simply add more to ensure the seam allowance is correct.

Remember to annotate your pattern. You can label it ‘Top Panel’, ‘Placket’, or something similar to keep it clear. Be sure to also add the cutting instructions: ‘Cut 1 from external fabric’. This will help you stay organised when you’re ready to cut your fabric.

And that’s it for today’s pattern modification! You’ve now created all the necessary pieces for your hidden zipper pocket. In the next post, I’ll show you how to assemble the pocket and sew everything together.

Prefer a Video? Check Out the Full Tutorial on YouTube

You can also see the exact process I walked you through today in a video format! I’ve created a detailed tutorial on my YouTube channel, where I guide you step-by-step through modifying your bag pattern to add a hidden zipper pocket. If you prefer watching the process, head over to my channel to follow along.

I hope you found this pattern modification tutorial helpful and that you’re excited to add a hidden zipper pocket to your favourite bag pattern! Modifying your patterns to include unique features like this one not only enhances the functionality of your bags but also adds a personal touch to every project. Whether you’re making a bag for yourself or as a gift, this little hack will make a big difference in how you use and enjoy your creations.

I can’t wait to see how you incorporate this hidden zipper pocket into your designs. Don’t forget to share your progress or ask any questions – I’m here to help!

Stay crafty!