How to check 1/4″ seam allowance: Pat Sloan’s simple trick

Raise your hand if it’s happened to you: you’re happily sewing along, creating a pile of pretty patchwork blocks. They look perfect—until you press and compare them. One block is too big, another is too small, and the rest are somewhere in between. How did this happen?!?

Best-selling author Pat Sloan will tell you: it might be your cutting. It might be your pressing. But most likely, it’s your ¼" seam allowance.

Even small inaccuracies can result in block-fitting hassles, row-sewing stress, and even sashing and border woes. So if you want to know how to fix a consistently too-wide or too-narrow ¼" seam allowance, read on for Pat’s sage advice!

Fixing an Inaccurate Seam Allowance
Excerpted from Pat Sloan’s Teach Me to Make My First Quilt

Sewing a consistent ¼"-wide seam allowance is very important in quiltmaking. Quilt blocks are generally building blocks of specific-sized squares, rectangles, and sometimes other shapes that fit together like a puzzle to create the final block in a specific size. And like a puzzle, if a piece is the wrong size, it won’t fit in its spot.

If your seam allowance is less than ¼", your units (or blocks) will be too big and your seam intersections won’t match. If your seam allowance is greater than ¼", your units (or blocks) will be too small, and once again, your seam intersections won’t match up and the final block will be the wrong size.

Even if you use a ¼" foot on your machine, you need to be sure you’re sewing an accurate ¼" seam allowance. Here’s an easy test to see if your seam allowance is accurate.

Place a small ruler (one with markings in ¼" increments) under the needle on your sewing machine. Slowly lower the needle by turning the flywheel by hand, until it barely touches the ruler. Adjust the ruler until the needle is on the ¼" line on the ruler and the edge of the ruler is ¼" to the right of the needle. Where is the ruler in relation to the seam guideline on your machine? Is it spot on? If not, you need to make some adjustments.

If your seam allowance is too wide, raise the needle slightly. Using the needle-position button on your machine, move the needle one position to the right. Carefully lower the needle and align it with the ¼" line on the ruler. If needed, repeat to move the needle one more position to the right.

If your seam allowance is too narrow, raise the needle slightly. Using the needle-position button on your machine, move the needle one position to the left. Carefully lower the needle and align it with the ¼" line on the ruler. If needed, repeat to move the needle one more position to the left.

Sometimes you simply can’t adjust the needle to match the seam guideline on the machine, because either you’re unable to move the needle to the correct position or your machine doesn’t have a needle-position button. In that case, place a piece of painter’s tape on the machine along the right  side of the ruler to make your own seam guideline that you can follow.

Recheck your seam allowance whenever you sew on a new machine, or if your blocks are not coming out the right size. Sometimes our minds wander and we’re no longer following the seam guideline.

Pat’s got tons of tricks just like this one in her “Teach Me” series of books—she’s taught thousands of quilters how to get better at their craft. Want to learn more with Pat too? Pick up one of her helpful books today:

Pat Sloan's Teach Me to Make My First Quilt Pat Sloan's Teach Me to Machine Quilt Pat Sloan's Teach Me to Sew Triangles Pat Sloan's Teach Me to Applique

Have you mastered a ¼" seam allowance?

  • Yep—and I re-check mine from time to time just like Pat.
  • It’s kind of hit or miss right now, but I’m going to try Pat’s tip!
  • Mastery seems like a looong way off for me . . . but I keep working at it.

Tell us in the comments!

38 Comments (leave a comment)

  • I usually feel like I am "spot on" until I start to measure by blocks and find out I am off a little. I really need to master the art of "a scant 1/4″! I have used my ruler to double check. That is a great tip!

    —Patty Fallon on August 17, 2018
  • I do this usually after I get the wrong size blocks and I have to unsew. I think I’ll try it before from now on. I am a terrible piecer no matter what.

    —Barb Walsh on August 17, 2018
  • I’m still working on it.

    —Susan MacLeod on August 17, 2018
  • I have a quarter inch foot for all my machines and that really helps. I do test it out by sewing and measuring with the ruler. I have also used an index card with the lines (they are exactly 1/4″ apart). I put the needle down on the first line and sew. You can use that to put tape down on your machine and it is easier than using the ruler.

    I read early on that it doesn’t really matter if your seams are 1/4″ as long as you are consistent. That is a bunch of crap, it does matter. When I teach a class I tell them it is very important to get a good seam and to cut perfectly. That way you don’t have to come up with ideas on making it work when it doesn’t.

    I have helped people put their blocks together when they didn’t have a good seam and it is a nightmare. It is also important to know how to square up your blocks or not do it at all. People cut off their seam allowances and don’t understand why they don’t come out. Once you master your seams and cutting, you can make just about anything.

    —Phyllis K Menefee on August 17, 2018
  • Thank you so much, it’s a great help

    —Sima on August 17, 2018
  • I learned the hard way , by ripping apart locks that didn’t match. So now I always use my 1/4 in. Foot and keep my eye trained to the edge of the fabric rather than the needle making sure that I stay in line right to the end of the piece. I found my errors were most often near the end of a strip so that after pressing the centres would not line up.
    Now it. Seems like a no-brainer! It is worth persevering as your results are your reward!

    —Alfreda on August 17, 2018
  • I check it nearly every time I sew. 1/4 in. seams do matter.

    —Cheri Bergeron on August 17, 2018
  • I got it down to a science on my main machine. But I do check it on my secondary machine when I choose to use it.

    —Lena on August 17, 2018
  • I’ve got it down to a science on my main machine. But I do a check when I use my secondary machine just to make sure it’s correct.

    —Lena on August 17, 2018
  • I try my best, but I’ll be the first to admit that I am not perfect and mistakes are a part of life. I don’t usually rip out seams, I’ll be more apt to compensate at the outside of a block (adjusting the width of a sashing strip seam for example). I don’t make my quilts for shows, I make them for people to use and most recipients don’t care about perfect points or an extra filler piece here or there. Although I try to do the best job possible, finished is better than perfect.

    —Teri N on August 17, 2018
  • I’ve measured using a ruler, but I also check by sewing two pieces together and measuring the resulting piece. Then I learn my 1/4 inch foot. Just bought a new machine (!) so I have to re-learn my placement even though it’s the same manufacturer.

    I consistently use the same thread but new quilters may not realize thread weight makes a difference as well. Even the thickness of the fabric matters.

    I agree with those who mentioned "it does matter". Good skills produce better results, even if they are ‘only’ for my family. I love my family and they love getting quilts. I once asked "aren’t you tired of always getting quilts from me?". The answer was a definite NO.

    —Janice on August 17, 2018
  • I have mastered a 1/4″ seam allowance and re-check often just like Pat. Would love to learn more of her tips and tricks!

    —Linda B. on August 17, 2018
  • I must admit that I use my 1/4 inch foot and don’t check. But I WILL, before I start my next project! As always, Pat Sloan has such down-to-earth, practical strategies.

    —Carol on August 17, 2018
  • I really reeeaaallllyy try. but sometimes I get so excited I get out of line..

    —Linda Clark on August 17, 2018
  • I’m still working on getting it right. It is better with the tape guide, but I have to keep checking too.

    —Linda Heckathorn on August 17, 2018
  • It is a continuing goal for me to be able to ALWAYS sew a 1/4 inch seam! I am blessed to have the laser guide on my sewing machine, but even with that great aide, I have to watch and be mindful of the where the needle is actually hitting the fabric. Thanks for the great tips Pat!

    —Laurel Smith on August 17, 2018
  • I could sure use Pat’s book, "Teach Me to Make My First Quilt". After this simple explanation of how to fix or maintain a 1/4″ seam allowance, I want to read the book and make sure I don’t develop bad habits. I’m a relative beginner, so I don’t think I’m too far gone to fix things now.

    —Teri D. Gailey on August 17, 2018
  • I was taught to cut by placing the line on the ruler on top of the very edge of the fabric. And then to sew with a "scant" 1/4 inch seam. These two together result in proper sizing. So I am curious how you cut if your seam is a full 1/4 inch as suggested above, so that the size still works out correctly.

    —Helga Diggelmann on August 17, 2018
  • Hit and miss. Mostly miss 😂 The issue is usually at the beginning and end where the seam becomes narrower. Apparently a stiletto helps. However, I find it annoying to use.

    —Rose-Marie on August 17, 2018
  • I am a lover of hand piecing and quilting but I would like to get some quilts actually completed in my lifetime so have turned to hand piecing. Getting the seams correct has been a nightmare and I actually hand piece faster. However, I am going to give this a try and see if it helps. As it has turned out, I have found I still love hand piecing best but absolutely fell in love with free motion quilting! If I can perfect my seams, I may be more productive in the future. Thank you so much for these tips!

    —Jane in NC on August 17, 2018
  • I had a terrible time until I tried something like Pat suggests. Now I have to move my needle to the right until it reads 42. I have had to train myself to do that and once in a while I forget and then I get to reverse stitch a few blocks. The 42 is perfect and this is on a relatively new machine.

    —Sue on August 17, 2018
  • It can be a challenge but my motto… "slow down and enjoy the journey"!!!!

    —Katherine Hanson on August 17, 2018
  • Well….not exactly:( But I keep at it. I’ve taped it off on my machine, I just need a steadier hand and eye.

    —Rachel on August 17, 2018
  • I use a quarter inch foot on my machine. When I discover that my blocks are not fitting together nicely, then I measure and discover where I am off. When will I learn to check my seam allowance before I am half way through my project? I really need to follow Pat’s advice.

    —Ann West on August 17, 2018
  • I won a heap of blocks once and had to unpick most of them as every one else’s blocks were not accurate. It was a nightmare as even after I re =did them they were not right as they were cut to size. Many I had to cut down after unpicking them to make them work. Since it was a group I could not throw them away as everyone wanted to see their blocks in my quilt. I also had to make more to fit the quilt and it was hard to make every thing fit neatly so YES it is not the best I had done to that point.

    —Heather Schimke on August 17, 2018
  • Yep I am a rechecker!

    —Lu on August 17, 2018
  • I use a 1/4 inch foot guide on my machine. I watch the thickness of thread; watch the line I sew on, and pressing carefully.

    I need to follow this tip to check before starting projects each time.

    —carol on August 17, 2018
  • hit and miss, but I know better and with my new-to-me fancy machine, I am going to do better

    —Roz Agulnik on August 17, 2018
  • It’s kind of hit or miss right now, but I’m going to try Pat’s tip!

    —Kaye Walker on August 18, 2018
  • I think so, but I will be checking with Pat’s tip!

    —Sandy Trachsel on August 18, 2018
  • I seem to have a hair difference in different machines that I work on. So I use the same machine on a project.

    —Mary Boyer on August 18, 2018
  • I am far too casual and tend to sew too quickly, resulting in seams that are not only NOT 1/4″ but also wavy and inconsistent. This is a good reminder to slow down nd pay attention if I want the best results. Thanks!

    —bookboxer on August 19, 2018
  • A guild friend of mine has a ‘ruler’ with tiny holes to show where the 1/4″ (and other) measurements are. I used it to determine which number on MY machine equates to 1/4″. On MINE it is 6.0. but I know others with the same make of machine use a different number setting. So I am aware that not all quarter inches are equal!!

    —Janet Gervin on August 19, 2018
  • A guild friend has a ruler with tiny holes to show where the 1/4″ (and other) measurements are. I used it to line up with my needle – my machine has settings to move the needle left or right. I found that 6.0 on MY machine gave me a 1/4″ seam. But I know others with machines by same manufacturer use a different number. Thanks for the hints on how to improve! I know it is important!

    —JanG on August 19, 2018
  • I am still learning and it’s kind of hit or miss right now. I plan on using Pat’s tip so that I consistently sew a 1/4″ seam. I understand how important it is!

    —Laurie Devers on August 20, 2018
  • I recheck my 1/4 inch seam every time is start to sew. Just to make sure!

    —Eileen Suderman on August 22, 2018
  • Pat Sloan’s simple trick is very good and effective. Tricks that helped a lot to me.
    vex 3

    —vin lookup on April 7, 2020
  • What are your thoughts on a "scant 1/4 in seam" ???

    Generally, as "scant 1/4″ seam" is about one thread less than 1/4″. It can vary, depending on your sewing machine and the thickness of the fabric you are working with. Best thing to do is to test your 1/4″ seam before starting a project to make sure your seam allowances are correct. I hope this helps! -Cornelia/Customer Service

    —Lori Campbell-Lewis on May 7, 2020

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