How to sew a stretchy maternity tank without a pattern

Learn to sew a stretchy, loose fitting maternity tank using a tank top you already have as a pattern. You can also check out a similar tutorial for a long sleeve maternity top here.

Supplies and materials

• Sewing machine
• Serger (optional)
• Stretchy knit fabric (like this cotton spandex jersey I used)
• Matching thread
• Clips or pins (clips highly recommended, as it’s easy to poke holes in knit fabric)
• Scissors
• Seam ripper
• Wrapping or packaging paper, or scrap paper taped together
• A writing tool for making your pattern

Getting prepared

First, choose the tank top you will be copying. The closer it is to what you’re going for, the better. You also want something that is a similar fabric to what you will be working with. My tank top was a rib knit that was actually a lot less structured than the fabric I used, but it was the closest I had.

Try your top on and take notes of of anything you want to change. I knew I wanted mine to be looser across the top, higher on the neck, have wider straps, bigger arm holes, and of course be longer and looser across the belly. I wanted a curved hem and was pretty happy with where the side seam ended.

Prepare your fabric. Wash and dry the same way that you plan to with the tank top. I didn’t actually iron my fabric at this point because jersey doesn’t get that wrinkly.

How to make a maternity tank pattern from a regular tank top

Step 1 – Turn your tank top inside out, fold it in half, and lay it on your paper. I have this nice wrapping paper from the Dollar Tree that has 1 inch grids on the underside. If you can find some, it’s so convenient! I knew I wanted my tank top to be looser, so I set it in 1 inch from the edge, which would give me an extra 4 inches all around. I also wanted the straps to be wider set, so this worked. But if you liked the strap placement, you would have to move the tank back and forth a little to trace the different parts of the pattern.

Step 2 – We are going to make the bottom wider. I made a mark 5 inches out from the bottom of the side seam. You could do up to 6 or 7. Then draw a line straight out from the armpit to this mark, adding a 1/2 inch seam allowance at the armpit.

Step 3 – Trace around the rest of the tank. You don’t need a seam allowance for the neck opening or arm holes (because they will have binding that ends up making them the same as how you cut them), but I wanted my straps to be wider and my neck opening to be way higher. It’s best to be more generous than you think you need to be here, because you can always cut some off. For the hem, I made it 5 inches longer (including hem allowance) and curved it up to my side seam.

These corners should be 90 degrees.

Cut out your pattern and grab your fabric!

Cutting the maternity tank out

Step 4 – Line up your pattern on the fold. Make sure the grainline is going straight up and down or your tank will twist over time. You will need to cut a front and back. I did them the same, but made the front neck line about an inch lower.

Make sure to notch your center front on the neck opening. This will make it easier to line up the neck binding later.

Step 5 – Pin or clip your side and shoulder seams together and sew. Use your serger if you have one, otherwise here are some instructions for sewing knits (stretchy fabric) without a serger.

Sewing knits without a serger

It will be easier if you make all of your seam allowances only 1/4 inch rather than 1/2. Otherwise you will have to trim your seam allowances after sewing.

Practice on some of the scraps from this project before actually sewing your top!

First, reduce the presser foot pressure slightly if you can (refer to your machine’s manual for this). My machine doesn’t have adjustable foot pressure, so I used a walking foot instead, which makes a big difference in the pressure. My machine came with a walking foot, but I also previously bought this set of sewing feet which comes with one.

Next, reduce the needle tension slightly. For my machine, I set it to 3 (normal is 4).

OPTIONAL: Zigzag along the very edge of your seam (I use stich length 2.5, width 5). This isn’t completely necessary, but it will make for neater and stronger seams.

Next, sew the same seam with a narrow zigzag stitch or the lightning bolt stitch if your machine has it (1/4 inch from the edge). Or you can use a straight stitch, stretching the fabric slightly as you sew.

Moving on!

Try on your maternity tank to see what you think!

Step 6 – Make any adjustments. I adjusted the neck opening and changed the shape of the armholes on the front, as well as made the curve a little higher on the sides of the hem. The picture above is with those adjustments.

How to make neck binding and armhole binding

Preparing the binding

Step 7 – Calculate the length you will need for your neck binding. Measure the circumference of your neck opening by lining up your measuring tape with the stitching line (1/2 inch in from the edge) and working your way all around. Multiply this number by .85 and add 1 inch for hem allowance. (My circumference was 22 inches, so this is my math: 22 x 0.85 = 18.7 + 1 = 19.7, so 19 3/4 inches. I rounded up a tiny bit to get a nice fraction). This will be your neck binding length. The width will be 2 inches.

Step 8 – Now use the same process to calculate your armhole binding.

Step 9 – Cut your pieces out and iron in half lengthwise, wrong sides together. Make sure to cut two armhole pieces!

Step 10 – Unfold them and sew the short ends together, right sides together. Trim the seam allowance.

Fold them back the way they were ironed and use notches to mark the center and quarter points. The quarter points will not actually match up with anything, but they are still helpful for making sure things are even.

Attaching the binding

Step 11 – Attach the neck binding. Use lots of pins or clips, matching up the seam to the center back of the shirt, and match the halfway notch to the center front notch. You will need to stretch the binding a little. Check the quarter notches to make sure it’s even on both sides. Mine were about 1/2 inch to the front of the shoulder seams. Sew and iron.

Step 12 – Attach the armhole binding in the same way. Match the binding seam to the underarm seam. The center notch will probably need to be a little bit in front of the shoulder seam, unless the back and front are perfectly even. You will need to stretch the binding a little, and make sure it is stretched more at the bottom part, where the shirt is more curved. Repeat on the other side, making sure your notches are all the same. Sew and iron.

Prepping the curved hem

I was actually pretty nervous to make a curved hem on knit fabric, because I often find that they flip up after washing. I couldn’t find any help for it online, even though I know I’ve seen this problem on lots of handmade and even some commercially made knits. After lots of experimentation and finally just going for it, I’m happy to say that this hem doesn’t flip up. Use the steps and tips below as a guide, but also make sure to experiment on scrap fabric to see what works for you.

Step 13 – Sew an ease stitch (aka basting or gathering stitch) 3/4 inch from the edge of the hem. This will just be a guide for ironing the hem up evenly. It really is a helpful step, so don’t skip it! You want to use the longest stitch setting on your machine so that it will be easy to remove once you are all done the hemming process. To make the stitches even easier to remove, I also like to lower my thread tension to about 2, sew on the wrong side, and sew the front and back separately, not quite to the side seams. That way I can just pull on the bobbin tails and they easily come out.

Step 14 – Iron the hem up along the line of stitches you just created. On the more curved parts, there will be some folds. Use lots of pins or clips to keep everything in place.

Tips for sewing the curved hem

Step 15 – Sew from the right side, a little less than 3/4 inch from the edge so that you are sure to catch the underside.

As far as settings go, this is the part that I recommend experimenting with so that your curved hem won’t flip up. The needle tension should be a little low (I used 3, normal for my machine is 4). You could use a twin needle, a zigzag stitch, or any other stretch stitch that your machine has. I actually used a regular straight stitch and stretched the fabric as I went because it seemed to work best. If you can reduce your presser foot pressure, you should (refer to your machine’s manual to do this). My machine actually doesn’t have adjustable foot pressure, so I used a walking foot, and it was really helpful. Remove your ease stitches, iron your hem, and you are all done!

And that is how you sew a flowy maternity tank!

What do you think? Of course, there are some small changes to the fit that I would make next time, but over all, I’m happy with it. Is this something you would try? Let me know in the comments below 🙂