Seam Allowance and When to Use the Scant 1/4 Inch Seam

Seam allowance is very important in quilting. When I first learned to quilt I was taught to always sew with a 1/4 inch seam. It wasn't until later when I started sewing more complicated patterns (meaning patterns with lots of piecing) did I realize that there is variance in the 1/4 inch seam. 

Each project can require a slightly different seam allowance depending on the fabric, thread and number of seams. That sounds overwhelming... I know! So let's get down to the basics and talk about seam allowance and when to use a scant 1/4 inch seam.

What is the scant 1/4 inch seam?

I had quilted for a while before I heard the term, which probably means I was making beginner patterns and didn't really need to know it. Which also means the scant 1/4 inch seam isn't important for all quilt patterns. 

As quilters we all want consistent 1/4 inch seams. That's the first thing I suggest beginner quilters should work on. And I always suggest using a 1/4 inch foot or a seam guide to keep things consistent. 

The word scant means "meager, a small amount". So by sewing a scant 1/4 inch seam you are adjusting your seams by a very small amount, like itty bitty. I know, it seems like it really shouldn't matter, but when lots of seams are sewn together in a small area, itty bitty becomes a noticeable amount. 

The scant 1/4 inch seam basically gives you that tiny extra bit of fabric which is used up when your fabric is pressed over your thread. Even with excellent pressing, fabric still needs to go over the thread and some is used up in each seam. This is not a big deal unless you have lots of seams in a small area. 

To make a scant 1/4 inch seam you adjust your needle, fabric or guide just enough to account for the pressing, fabric thickness and thread weight allowing a slightly smaller seam. 

An example of when a scant 1/4 inch seam would be important...

The Northwest Stars Quilt Pattern

As you can see below, the center of each star is made of thin fabric strips pieced together. When a regular 1/4 inch seam is used the center unit measures slightly too small to sew into the block.  

Another example is the Adelaide's Cabin Quilt Pattern. 

You can see the center Log Cabin block contains a lot of seams, but so do the sides. If the sides are not sewn with a scant 1/4 inch seam then they will not measure the correct width which can be super frustrating. 



I experimented with pressing these seams to the side and open. I found that pressing them open allowed for much flatter seams and more accuracy. But I suggest you follow the pressing guidelines of the pattern you are sewing.

How to adjust your seam allowance?

Check your sewing machine manual to see if your needle can be adjusted. Even on my beginner Janome Sewing Machine the needle can be manually moved to account for seam allowance. If the needle cannot be moved, use a seam guide or tape to experiment with the correct placement of your fabric as you sew. It's not going to be that much different than your normal 1/4 inch seam. But a little bit can make a big difference!

How do I know if my seams are correct?

The best way to know if your seams are correct is to experiment with the project you are working on. I suggest doing a practice block to check the seams with a ruler. I know, I would much rather jump right in and start my project, but checking will cause less frustration and more accurate projects in the long run. 

If you don't want to make a whole test block, then get out your ruler and measure as you sew. After pressing each seam check to make sure that the unit is measuring the correct width and you are on track.

Remember: You will loose 1/2 inch of fabric each seam. 

Example: If you are sewing (2) 2 1/2 in. strips together. After pressing they should measure 4 1/2 inches wide.  Because 2 1/2 + 2 1/2 = 5 - 1/2 (for the seam) = 4 1/2 in. 

Another way to measure: 

You can see in the image below, each strip in this unit measured 1 1/2 inch wide before sewn together. Once sewn together each strip measures 1 inch wide. 

Because my ruler lines up at the 1 inch mark with each seam I can tell my seam allowance is correct. 

Here is the biggest thing... Don't let seam allowance scare you off from quilting! Even if your seam allowance isn't perfect, which mine frequently are not, it's your project and a little imperfection adds to the uniqueness. 


Most of all... have fun!