Accurate Piecing — That 1/4″ Seam

Intricate piecing can be beautiful, but every extra patch means an extra seam, and every extra seam means another opportunity for errors in sizing.

Consider the border I’m working on now. It’s just 24 half-square triangles that finish at 2″. The length of border should finish at 48″. Each of the 24 HST has only one seam. And there are 23 seams attaching the HST to each other to create the border. That’s 47 seams in total. Now, only consider the vertical seams attaching them to create the border length. If each seam allowance is off by 1/16″, that’s not much, right? But 1/16″ x 23 seams is 1 7/16″, or almost 1.5″. That doesn’t even include the error potential when making the HST.

So much for potential error. Here is the real thing. Here are two halves of one border strip. They really do have the same number of HST.


Each part is supposed to measure 24.5″, unfinished. The first one I made (top) is slightly short, so I adjusted the seam allowances so the bottom strip would be slightly longer. Oooops! It’s more than a half inch longer. Now I need to fix it by making a few seams wider, to take up the extra fabric.

Everyone faces the question sometimes of how to make a block or border fit. When I was a beginning quilter, I usually made block quilts. My seam allowances were usually too big, which meant my blocks were too small. I learned a lot of ways to improve my seam allowance, and a lot of ways to fake it or fix it. Here are a few.

It starts when you prep your fabric. Some people prefer to use washed fabric and some don’t. I strongly prefer washed, for multiple reasons. Either way, soon you will cut fabric, and before cutting, you need to press it. (Yes, you really do need to press it.) 

I press carefully with a hot steam iron, because cutting is more accurate on flat fabric. Many people recommend starching fabric to stiffen it. I do now and then, especially if I’m working with a cotton that’s flimsier than usual, but it isn’t part of my standard practice.

When’s the last time you changed your rotary cutter blade? If your cutter blade is dull, it will drag the fabric rather than slice through it. You may need to cut through parts multiple times, risking moving your ruler slightly. A sharp blade will give you better cuts with less force. A bonus is that sharp blades are less dangerous, too!

My cutting surface is a comfortable height for me to use while standing. It’s a plastic-topped, folding “buffet” table, the type that can be found at most discount stores. It is much too low by itself, but I have it raised with PVC pipes slipped over the legs. The pipes are cut to raise the table about 5 inches. Other people find that bed risers work well to raise their table. The extra height helps with comfort, but it also helps with precision, because I’m not bent so far over my work.

I stand with my shoulder directly lined up with the line of cutting, so my arm moves straight forward, not at an angle. This helps keep the blade moving in the right direction, so I don’t accidentally push the ruler offline.

Lighting is another element. Enough light, in front and above you, makes your work easier and more precise. Besides the overhead light, I have LED utility light strips on either side of the room where I cut.

As I was learning to quilt, two cutting strategies led to big improvements in my piecing. First, cutting along the selvage provides more accurate strips as compared to cutting across the width of fabric (WOF.) The grain is more stable and doesn’t shift as much when piecing. Besides that, you won’t need to worry about whether the fabric was cut from the bolt on grain. (It rarely is, which requires adjustment if cutting WOF. In addition, you may lose significant yardage when squaring up for cutting WOF.) If the selvage is gone, you can tell which direction is “with” the grain by which one has less stretch when you tug it.

Cutting along the selvage is especially important when cutting border strips. You’re much less likely to have waves and flares when attaching the border. (Of course, this also requires measuring the border length accurately, and pinning the strip in place before stitching.)

Second, don’t try to cut through more than four layers of fabric at a time. More layers are harder to cut through, requiring more force from you and increasing the opportunity to shift your ruler with the movement of the blade.

Finally, measure twice, cut once. Make sure the ruler lines are parallel to the lines on the mat (if using them) or lined up exactly with the edge of the fabric. Too often I’ve cut on a line crossing from 1/8″ to 1/4″, or that type of thing.

When you take precisely cut pieces to the sewing machine, how can you get good seam allowances? Again, ergonomics, or your comfort, plays into it. If you can, use a desk chair with adjustable height. You need to be able to see and reach your workspace easily to have good control.

Pins: sure, they take time. Time to put them in, time to take them out… they seem like a hassle. I rarely pin small units. But when I assemble bigger blocks I usually use them. And when I sew long lines, such as rows of blocks or borders, I pin a lot, every couple of inches. (Twice as many pins do not take twice as long to set or pull.) Thin pins are best, as they don’t distort the fabric and are easier for your machine to cross if you don’t pull them first. Pins also allow you to ease in the fabric without making little darts when the two pieces don’t match up exactly right.

I use a 1/4″ foot to make my seam allowances better. It has a little “fence” to guide my fabric edge. Still I need to know whether to nudge my fabric against the fence or leave a thread width away from it. Some machines have adjustable needle positions, but not all 1/4″ feet can accommodate a change in position. If not, you still need to be in charge.

If you don’t have a 1/4″ foot, there are a lot of sources for tips (here and here, for example) in getting a better seam allowance.

A key strategy to avoid my problem above is to check sizing regularly. Because my HST finish at 2″, each pair of HST should finish at 4″. A set of four of them should finish at 8″. If I had checked my piecing before stitching all the units together, I could have adjusted my seam allowances before creating the whole strip.

And no, you’re not done yet! Pressing a stitched unit or block is the last part of the puzzle. As with fabric prep, when you press units, use an up and down motion, rather than dragging the iron across. Most sources recommend pressing toward the darker fabric. Sometimes this is practical and sometimes not. You can find more tips for pressing here and here.

As you can see, there are a lot of different elements that play into piecing accuracy, not just your time at the machine. Little changes can add up to a lot!

What choices do you have when your piecing isn’t as good as you’d like? It depends on your need for perfection. One option you can always choose is to add some if the border or block is too small, or cut some off if it is too large. This “wonky” or “liberated” style is historically traditional and works great for some styles of quilts.

I am no perfectionist, but I do like things to be “pretty good.” For me that means fixing some and fudging some.

Fixing generally requires re-doing at least some seams. For my strips above, I want to shorten the longer one about a quarter inch. I will re-stitch four or five seams with a little wider seam allowance. If my strip were too short, I’d take out a few seams and re-stitch with a narrower seam allowance.

Fudging is possible in a lot of cases. If you’re trying to attach a border and the length is off by 1/4″, or even 1/2″, go ahead and pin a lot to ease the extra fabric in. If my border is too long, I also might “adjust” at each end. I pin about 1/8″ of border beyond each side of the quilt center. This gives me another 1/4″ I don’t need to ease in, and the loss is barely visible. If my border is too short, I can adjust it the other way.

Similarly, you often can trim edges of blocks or borders, and no one will know but you. Some blocks are easier than others. If your flying geese are too large, make sure the “beak” side has a nice seam allowance to preserve the point. Trimming the other edges won’t be very noticeable.

Remember, once the project has been quilted, many of these small errors disappear into the dimpling of the surface.

And it’s always good to remember, you might be your own harshest critic. If you wouldn’t scold a friend for her piecing mistakes, why would you scold yourself? If it’s important to you, try a few ideas above to improve your accuracy. If it’s not, just keep having fun and enjoy the process!


20 thoughts on “Accurate Piecing — That 1/4″ Seam

  1. snarkyquilter

    I’ve given up on accurate 1/4 inch seams and gone for what Mary Ellen Hopkins called your PPM, your personal private measure. My theory is that as long as I’m consistent, the results should work out.I always seem to make my stuff a tad too small. Of course, it’s another story for blocks meant to be shared. Also, for long rows of HSTs or flying geese I tend to freezer paper piece them, so I get the length required.

    1. Melanie McNeil Post author

      Yes, if it’s for yourself, it’s for your own standards. Bees and swaps and such are another matter, and one reason I usually don’t join in on those. 🙂 Good job on the freezer paper work. I have done a little of that but not much. Another thing to work on…

  2. Patricia Differding

    As a new quilter these hints are very helpful. I struggled with 1/4 inch seams until our teacher suggested the foot with fence that you mentioned. It’s encouraging to see an experienced, skilled quilter also makes errors. 🙂 Thanks for the suggestion for preventing and fixing them.

    1. Melanie McNeil Post author

      You’re welcome, Patricia. And always remember that struggle is just part of the process. When you find yourself frustrated, take a deep breath and a break, ask for help if you need it, and try again. That’s how we all have to do it.

  3. myquiltprojects

    This is the part of quilting that has drove me nuts for years. I finally have it down. I figured out that the thread was the culprit. Using too thick of thread took away a just a thread thickness which adds up. Now I use lighter weight thread for piecing and a dowel rod for pressing with no steam and sometimes a little starch.

    1. Melanie McNeil Post author

      Oh what a great point. Yes, there is a substantial difference depending on what thread you use. I also try to use lightweight (#50 weight) thread. Thanks for the reminder.

  4. norma

    I love my 1/4″ foot. I’d never be accurate without. I also know that I’m not fantastically accurate with machine piecing and do anything intricate with English paper piecing.
    I will study your post & try to improve

    1. Melanie McNeil Post author

      My 1/4″ foot doesn’t give me exact 1/4″ seams, but I come much closer than I would without it. I just try to balance my desire for things to be “pretty good” with the need to keep moving. 🙂

        1. Melanie McNeil Post author

          I can’t adjust it while using the foot. But And because of the math for triangles, “exact” isn’t exact anyway, so one still needs to know what their own machine and settings do. Thanks.

  5. katechiconi

    I have a quarter inch foot I never use, as over time the thin metal ‘fence’ has splayed outwards, rendering the measurement uncertain. I now have tape on the base plate and a standard foot where I have marked an exact quarter inch. Between the two, I manage enough accuracy for my own purposes, although if I was making quilts like yours, with lots of accuracy-critical piecing, I’d work harder at it! I do agree that accurate cutting and subsequent pinning makes a huge difference.

    1. Melanie McNeil Post author

      I don’t work very hard at it, truthfully. But to me it’s crucial to have the pieces FIT, however you get that done. If they don’t fit, corners will splay or borders will ruffle. Neither one is happy outcome. So faking it often works, and believe me I do a lot of that. When I can’t get away with that, I go ahead and fix it. 🙂


Thanks for your comments. I don't check them often. Please email me if you have questions.

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s

This site uses Akismet to reduce spam. Learn how your comment data is processed.