How to Sew a Perfect Quarter-Inch Seam for Quilting – New Quilters

Photo of sewing machine presser foot with ruler and blue painter's tape seam guide

Psst! Don’t tell the Quilt Police, but sometimes I’ve had trouble making my blocks come out the right size. How about you?

Do any of these sound familiar?

  • Your quilt blocks end up a bit too small.
  • The points of your stars or triangles get chopped off at the tips.
  • The seams on your quilt tops don’t line up perfectly with each other.

What’s going wrong?

If your quilt blocks and tops don’t always turn out the right size and shape, one of the first things to check is your seam allowances. Seams that are just a whisker larger or smaller than a scant quarter inch can cause you a lot of trouble. (I know this from experience.)

If you can learn to sew a consistent quarter-inch seam, your quilt blocks will turn out the right size every time, and your rows will fit together perfectly when you assemble the blocks into a quilt. After years of giving lip service to the concept of perfect quilter’s seams, I decided to test my accuracy and walk my talk today.

Seam Allowance Definitions

The seam allowance is the distance between your line of stitching and the raw edge of the fabric you’re sewing. One-quarter inch is the standard seam allowance used in almost every quilting pattern. Experienced quilters often advise beginners to try for a “scant” quarter-inch seam—a seam allowance that’s just a thread or two less than a quarter-inch.

Why Do You Need a SCANT Quarter-Inch Seam?

If your seams measure exactly a quarter-inch from the stitches to the edge of the fabric, your blocks will come out just a tiny bit too small. This happens because when you press a seam after sewing, the top layer of fabric is folded over to one side. This makes the block shrink slightly. The more seams in your blocks, the more shrinkage you’ll experience. This can cause real problems when you assemble a bunch of blocks into a quilt top. Leaving a scant seam allowance is most important when you make complicated patterns with lots of seams.To compensate for the shrinkage and make sewn blocks come out exactly the right size, you’ll need to use a seam allowance that is just a hair under a quarter-inch.

How to Achieve Consistent Seams

Here are some suggestions for making your seam allowances come out the same size every time. No matter which method you use, you should still test your results to make sure you aren’t off by a hair in one direction or another. (More on that below.)

  1. Use a quarter-inch quilting foot. Most sewing machines today offer a special foot with a built-in guide that helps you sew an exact quarter-inch seam. Not all machines have them. My fancy but finicky Pfaff 2140 has a quarter-inch foot accessory, but the Brother 1500s I now use for almost all my piecing doesn’t have one. So it’s option 2 for me!
  2. Create a seam guide on your sewing machine. I find this technique helpful even when I’m sewing with a quarter-inch foot. I can run the guide well out in front of the needle to help me align the fabric as I sew along. To create a guide, you will need a way to mark your sewing machine bed. The ideal seam guide is thick enough to make a little lip that keeps your fabric in place as you feed it into the machine. Some options I’ve seen here and there around the web:
    • Marker line drawn on the machine bed
    • Stack of blue painter’s tape. This is what I use. I stick several strips on top of each other to create a bit of an edge to align my fabric. Here’s the blue tape guide on my sewing machine.Photo of sewing machine presser foot and blue painter's tape seam guide
    • Thick foam tape like a Dr. Scholl’s foam bandage
    • Piece of flexible cardboard taped to the machine bed
    • Stack of Post-it notes
    • Thick rubber band fitted around the sewing machine’s free arm (if your sewing machine has a free arm.) Thanks to reader Sue Hamner for this suggestion.
    • A commercially available sewing guide that you can buy at quilt shops or fabric stores. Dritz makes a magnetic seam guide which is supposed to work on any machine. I’ve also seen an adhesive seam guide from Collins that comes with a little measuring device for pinpoint accuracy. I’m leery of using magnets on my electronic machine, so I prefer adhesive to magnetic.
    • A piece of weatherstripping foam. The thickness of the foam creates that little ledge that helps keep your fabric in proper alignment. Use the sticky side against your sewing machine bed. It is easy to remove when needed. Thanks to reader Mary Sloan for this suggestion.

How to Locate Your Seam Guide Accurately

Accuracy is the word here, so you’ll need to do a bit of measuring.

  1.  Put a see-through cutting ruler under your sewing machine’s presser foot and lower the needle until it touches a spot just a hair to the right of the quarter-inch mark closest to the right edge of the ruler. (You can also use a piece of graph paper and touch the needle to the first quarter-inch mark on the right side of the paper.)
  2. Using the right edge of the ruler or graph paper to align your tape or sewing guide, stick the guide on the machine bed just in front of the feed dogs. You don’t want the guide to interfere with those dogs!Photo of sewing machine presser foot with ruler and blue painter's tape seam guide
  3. Run your fabric along the edge of the guide when you feed pieces under the sewing machine needle.

How to Test Quilt Seam Allowances for Accuracy

No matter what method you use to align your seam, you should check yourself with this quarter inch test.

  1. Cut three short, 1½”-wide strips of fabric like this: Photo of three fabric strips with rotary cutter
  2. Sew the three strips together.
  3. Press the seams to the sides, then measure the center strip. It should measure EXACTLY 1”. If it is narrower or wider, adjust your seam guide and retest, then check again.

I decided to test the painter’s tape seam guide I was using on my sewing machine. I sewed the three strips together, pressed them, and measured. On the first try, the center strip measured less than 1 inch. It was TOO SMALL.Photo of ruler on top of three fabric strips

I moved the tape a bit closer to the sewing needle and tried again. This time, the center strip was TOO BIG. I had moved the seam guide too close to the needle.Photo of ruler measuring fabric strip set

On try #3, I got the center strip JUST RIGHT. Now my seams and my blocks should come out the right size.Photo of ruler measuring fabric strip sets

The test didn’t take long at all — about ten minutes total. Why did I wait so long to do this? Readers, I challenge you to try this test yourself and let me know how it turns out.

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Felicity Walker
 

Felicity Walker is the author of the best-selling Quilting for Beginners book series and other books for quilters. She has been quilting for nearly twenty years and loves finding easier, faster, and more fun ways to make quilts.

  • Mary Sloan says:

    I use weather strip it is sticky on one side and just thick enough to keep fabric from moving over the edge. Easy to remove if a larger seam is needed

  • Mary Lee says:

    I am a retired English teacher and a visual learner, so your tutorial is a Quilt-saver for me! This trick should be an intro to all quilting seminars. Can’t wait to put the marker in place, the tutorial nearby, and SEW away.

  • Marianna says:

    Excellent advice, Felicity. I have taught quilters kindergarten for years. My student are always grateful (down the line) that I forced them to master the scant quarter seam first.

  • Ginny says:

    What about attaching a small ($6) laser light to your machine aimed at a scant quarter? I used double stick Velcro.

    • Good idea, Ginny. I’ve tried using the laser to create a line for sewing the center seams in a half-square triangle block, but I haven’t mastered the art of placing the laser on my sewing machine head. I’ll have to give it another try.

  • Patti says:

    I have a top loading bobbin with a little plastic door that I have to pop off to refill the bobbin, so i cant put anything over it. It’s hard to get the 1/4 seam for me.

    • I also have a top-loading bobbin with a clear plastic lid, but I find I can still put a painter’s-tape seam guide on the right side of the seam allowance without interfering with the bobbin. If that’s not possible for you, that’s a real shame! You’d think the sewing machine people could come up with a better bobbin design.

      • Linda says:

        That isn’t too big of a deal for me even though it would require moving it each time I was sewing but i can’t even do that because it interferes with the feEd dogs!

    • KathyDe says:

      My Elna is the same. I used the painters tape trick and then using an exacto knife, I scored down the seam of the plastic drop in bobbin cover. Works fine.

  • Rebecca says:

    Thank you!! Now my 12 & 1/2″ blocks should be 12 & 1/2 and not 12″. Drove me nuts!! Lol. Now to learn how to cut accurately.

  • Mary says:

    Thank you! My two biggest issues are the 1/4 inch seam allowance and thinking I did well but when matching up, it’s off. Also cutting accurately to begin with.

    • I am still working at both of those even after many years of quilting. Some people are just born with that precision gene, and others of us have to keep improving slowly over the years.

  • Barr says:

    When you have to change the thread , you then have to remeasure correct?

    • Thanks for the question, Barr. Yes, I would remeasure when I change the thread — any time you lift the presser foot, you can introduce changes. Best to meausre again just to be sure.

  • Martha says:

    I bought the Dritz magnetic seam guide, it was so strong it moved my bobbin and machine wouldn’t sew correctly. Once I removed the guide, my machine worked fine.

    • Wow, that’s not good! I have an electronic machine and wouldn’t dare put a magnet anywhere near the motherboard. Sorry you had that experience. Maybe a few layers of trusty old blue painter’s tape layers are a better solution.

  • Auntiepatch says:

    I made my own clothes in high school and didn’t sew much after that. When my son and his girlfriend decided to move to Berkeley, I whipped out a Disappearing Nine Patch top for them. I didn’t have time to send it out to be quilted so I quilted it row by row with block-size batting between the top and bottom layers. It turned out lovely and they love it.

    That first quilt awakened a sewing sickness and I’m now turning out one after the other. Is there such a thing as QA?

  • Judy Gordon says:

    My first quilt was a cowboy quilt for a little boy. It was truely a learning experience because I had sewed for about 50 years but never quilted. I turned out fair but after close to 75 quilts later, I am really much more confident about my ability to put together something that I can say I am proud of.

  • Helen fox says:

    Hi I teach sewing to all abilities and I make sure that my guys can handle hand sewing as well as sewing machines.
    Re sewing by hand and keeping things straight and even .Try putting a mark on the side of your thumb to tell you what your ideal seam allowance should be.
    I use white micro pore surgical tape for this or mark directly onto the skin if the persons willing .cheap and simple.

  • Marion says:

    They have a 1/4 inch tape to use on the edge of your fabric as a guide.

  • Laurie Brunson says:

    I found in the scrapbook section of my Joanns an adhesive grosgrain ribbon and it works perfectly as a seam guide. It’s thick enough that cotton quilt fabric will ride along the edge, and yet not too sticky when you want to remove it or enlarge the seam allowance for clothing construction

  • Felicity Walker says:

    Glad to have helped, Erin.

  • Dolores says:

    I must try this, now to make perfect Block

  • Polly says:

    I use a strip of moleskin to make an edge at the 1/4 mark. I never heard about using the scant 1/4 in. Thanks for the advice, my pieces should fit better knowing that.

    • cdmwriter says:

      Great idea, Polly! Moleskin has the thickness that really helps guide the fabric. I might steal some from my husband’s hiking emergency kit and give it a try.

  • Sue Hamner says:

    I marked the quarter inch seam, then put a rubber band over the marking to give the lip. Works!!

    • Felicity Walker says:

      Great idea, Sue!

    • Brenda says:

      I love this idea, because it’s easy to slide the band over out of the way when sewing other projects. Like seams down the middle of my 1/2 blocks. Just had trouble finding the perfect rubber band, had to fit pretty tight, and be thick. My granddaughter’s make perfect seams!

  • Caroline says:

    Hi Felicity
    I had a lot of problems with my electronic machine not sewing properly and each time I took it to be tested it ran perfect and turned out that my magnetic pin holder that I had beside my machine was causing all the problems so after getting rid of it my machine now runs perfectly

    • Felicity Walker says:

      Oh, Caroline! Problems like that are so very frustrating. I am really glad you found the solution. Readers, be aware that anything magnetic such as Caroline’s pinholder or lights that attach to your sewing machine with magnets or magnetic seam guides can cause problems for electronic sewing machines. I guess that’s an argument in favor of sewing with an old-style mechanical machine.

  • Jackie Anderson says:

    Very useful tip

  • Carol says:

    No seriously, it really, really can’t be this simple… I almost feel like you are tricking ME!!! I am a FOURTH generation professional sewer, I gave dozens of aunties, cousins & nannys, and I have sewed for 40, yes, yes, 40 years, and I find this tiny little trick that has changed my life!
    You deserve a Nobel Prize of some description, yes you do. I love you by the way, I think I’ll keep an image of you in locket close to my heart!

    • Felicity Walker says:

      Aw, we’re blushing! So glad to have been helpful to you, Carol. I can’t tell you how much I wrestled with the perfect 1/4″ seam. I’m not one of those quilters who has an inborn gift for accuracy. But you can learn to be accurate even if you don’t have the gift already.

  • APRIL says:

    I STRONGLY advise against using the magnetic guide. I used the magnetic guide on two of my machines and it caused major problems with the metal bobbin shuttle jumping while I was sewing. To remedy this I had to stop using it for at least a week for all of the magnetic field to wear off before the machine would run normally again.

    • Felicity Walker says:

      Thanks for that advice, April. I haven’t tried a magnetic guide myself. I have a fancy one on my new sewing machine, and before that I always stuck with a few layers of my trusty blue painter’s tape.

  • Lynn Dedousis says:

    new quilter needs lots of help

    • Felicity Walker says:

      Lynn, if you have any questions, send us an email or post a comment and we’ll be happy to help as best we can. Glad to welcome you to the world of quilting. It’s a wonderful world and a (possibly) all-consuming creative interest.

      • Peggy Waller says:

        What about hand sewing??

        • Sorry, Peggy, I guess our pro-sewing-machine bias is showing! I just looked for articles about seam allowances for hand quilting and came up empty. But I am guessing that you can mark your seams with a ruler and a marking pen or pencil and just stitch along the line to achieve a neat quarter-inch seam on a hand-pieced block. On curved blocks this would be more difficult. Is anyone reading this who is a hand quilter?

          • Suzanne says:

            You would have to use a very fine pointed pencil or a very fine pointed pen because if it you made it to thick you might not get your 1/4 inch seam right.

          • That’s an important point, Suzanne. Precise marking is key to precise cutting and sewing. (A lesson it took me years to learn!)

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