The Quarter-inch Seam

Quilt blocks are sewn with a quarter-inch seam. Sometimes the pattern calls for a ‘scant’ quarter-inch seam. It’s such a small difference, what could it possibly matter? And why is an exact quarter-inch seam so important? Let’s break it down and look at the reasons.

A quilt block is made up of many seams. Sometimes there can be 8 seams across the block.

  • If the quarter-inch seam is even 3/16 too large, the block will measure 1/2″ too big (8 x 3/16).
  • If the quarter-inch seam is 3/16 too small, the block will measure 1/2″ too small. That’s the seam allowance for joining to the other blocks.

There is a good way to make sure the quarter-inch seam on the sewing machine is indeed a quarter-inch.

Set up your sewing machine to quilt. Use the foot you normally use – make sure everything is as it usually is.

  1. Cut (3) 2″ squares, 2 of one color and 1 of a different color. This just makes it a little easier to see. The thread color in your machine should have high contrast to your fabric. You want to be able to see it clearly.
  2. Sew 2 squares together of different colors.
  3. Sew the remaining square to the other side of the 1 color. See below – this is what you should have.


Open it up and press your seams in the way you usually do it. Now, measure the strip. It should measure exactly 5″.


If it’s off even an 1/8″, it needs to be adjusted. Here are some things to check –

  • Measure both seams. Are they exactly 1/4″? If they are, that’s great!
  • Let’s check the pressing. Try pressing the seams open and measure your strip again. Is it 5″ now? Great! What? It’s not? Okay, let’s check one more      thing.
  • Using your clear, 6″ ruler place it under your presser foot. Very carefully turn the hand wheel until the tip of the needle just barely touches the ruler. Now, you know where the edge of the quarter-inch is. You can mark that edge with a Sharpie, or a strip of tape.

Repeat the 3-square sewing exercise, and measure again. Results should be perfect! Now that you know where the quarter-inch is, quilt blocks will be much happier.

Watch the video below for information on a scant quarter-inch seam. This measurement is also very important.

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Enjoy your next quilt block!


About Karen

Karen has been a seamstress since the age of 9, and a quilter for the past 25 years. She's enjoyed all sorts of quilt adventures including quilt making, hand quilting, quilt design, quilt magazine publication (Cotton Spice) and now she's the editor of The Quilt Pattern Magazine.  She wrote a book - Log Cabin Quilts: A Brand New Story by Karen Murphy (I've since remarried) with Martingale and Company in 2004. Karen also enjoys knitting, writing and editing, and hunting treasure in thrift stores and estate sales. She has 14 grandchildren and one on the way. You can read her blog on writing and editing at  Or visit her Etsy shop where she sells her primitive stitchery designs


  1. Hi Karen, thanks very much for this information on a “scant” quarter inch seam, its always good to know the correct way to do something, especially when piecing a quilt, and the seams need to be accurate!

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