What is a Scant 1/4 Inch Seam Allowance for Quilting?

And how to sew an accurate scant 1/4 inch seam allowance? This tutorial will show you why you should use a scant quarter-inch seam and how to get it perfect every time!

If you’ve been quilting for a while, I’m sure you’ve heard of it. And if you haven’t you’re bound to come across sooner or later.

The mysterious scant ¼’’ seam allowance. I know it can sound scary, but it actually isn’t. It’s actually super cool and will take your piecing from ok to perfectly accurate. And with some handy tricks, you’ll be getting a perfect scant ¼’’ seam allowance every time.

What Is The Standard Seam Allowance For Quilting

If you’ve ever followed a quilting pattern before, you probably know that the standard seam allowance for quilting is ¼ inch.

Pretty much every quilt pattern out there uses this standard ¼ inch seam allowance, which is added to the cutting dimensions and the construction method to yield the required-sized quilt blocks.

But this is where things get complicated interesting. Because there’s the 1/4 inch seam allowance and there’s the SCANT 1/4 inch seam allowance.

What Is A Scant ¼ Inch Seam Allowance?

In sewing and quilting terminology, “scant” refers to a measurement that is slightly less than the precise measurement. So a “scant 1/4 inch” seam allowance is just a tiny bit less than the regular 1/4 inch seam allowance.

What Is The Difference Between 1/4 And Scant 1/4?

A picture says a thousand words, so I made an example of each of these two different ‘standard’ seam allowances.

The example with the blue squares uses the ‘exact’ ¼ inch seam allowance. The example with the pink squares uses the SCANT ¼ inch seam allowance.

As you can see, the quarter-inch mark on the ruler on the blue square is right on the edge of the fabric. On the pink square it’s a tiny bit to the right. That’s because the SCANT ¼’’ seam allowance is just a hair’s breadth (usually about a thread’s width) less than the ‘full’ ¼’’ seam allowance.

Why Do You Use A 1/4-Inch Seam Allowance For Quilting?

Now the real question is – why would you even bother with the SCANT ¼ inch seam if it’s so much easier measuring and sewing everything with a ¼ inch?

Let me ask you this. Have you ever found yourself making a quilt, following the pattern down to a T, and somehow ending up with blocks that are too small? 

Sometimes, it’s not really a problem (just a curiosity). Other times, it becomes practically impossible to sew different blocks together and you just can’t figure out why.

Well very often, the reason this happens is because you’re not using a SCANT ¼’’ seam allowance (but a ‘regular’ ¼’’ seam allowance). Why?  Let me explain with an example.

Why A scant Quarter Inch Produces More Accurate Blocks

Let’s say you want to make a simple patchwork quilt using 3’’ fabric squares. When you sew two fabric squares together with a ¼’’ seam, you’d think you’ll end up with two adjacent 3’’ x 2 ¾’’ rectangles (because you sewed ¼’’ into the seam allowance).

In reality, if using a true ¼’’ seam allowance, you’ll probably end up with two 3’’ x 2 23/32 ‘’ rectangles (so something like a 1/32’’ less than 2 ¾’’).

Why? Because when you open the seam and press it to one side (which is what we recommend) or press it open, you lose some material. This is because of the thickness of the thread itself and the fabric bulk that occurs around the seam. What this means is that inevitably, your blocks will end up just a tiny bit smaller.

This might feel insignificant when sewing together just two pieces of fabric, but trust me those 1/32-inch mistakes add up.

Here’s an example of what happens when you sew together five 3’’ squares using a ¼’’ vs. a SCANT 1/4 inch seam allowance.

Basic math will tell you that – in theory – five 3’’ squares sewn together with a ¼’’ seam allowance should yield a 13’’ strip. However, as you can see in the picture below, it actually yields a 12 ⅞’’ strip. That’s because, with each additional seam, the tiny bit of extra fabric that gets ‘used up’ by the bulk adds up.

You can also see that the segments aren’t 2 ½’’ wide, but are actually a tiny bit narrower.

On the other hand, if you use a scant 1/4 inch seam allowance, the resulting strip is in fact precisely 13’’. And the segments are 2 ½’’ wide, as expected.

When To Use A Scant ¼ Inch Seam Allowance?

Here at DTQ, we advocate a scant ¼’’ seam allowance at all times. That’s because we find it’s easier to stick to one measurement for all projects, and not worry about which seam allowance to use when etc.

I am pretty sure that after seeing the difference between the scant and the ‘regular’ ¼’’ seam allowance you’ll be more than happy to adjust your seams.

However, there are projects that don’t actually require you to use a scant ¼’’ seam allowance. It’s not wrong to use it (!), but you’ll be okay with a regular ¼’’ as well. 

This is when sewing very simple quilts – like a simple quilt with squares or any other pattern where the seams are evenly distributed across the quilt top. You will end up with a slightly smaller quilt top as a result, but other than that it will turn out fine. 

Another example is when sewing quilt blocks with very few seams – but here it’s mostly because the error doesn’t multiply as often, so the final result is not that different.

I’ll repeat what I said – we stick to a SCANT ¼’’ seam allowance for everything we sew. This way we know we’re always getting accurately pieced blocks that are the size they were supossed to be!

I recommend doing this before every new project. That’s because the perfect scant 1/4 ‘’ seam allowance can be different depending on what materials you use and the weight of the thread you’re sewing with.

Special Tools for a Scant 1/4 ‘’ Seam Allowance

I know I said you don’t need any special tools for achieving a scant ¼’’ seam allowance. But that doesn’t mean they can’t be helpful.

Sewing Machine Foot For ¼″ Seam Allowance

Many quilters (including myself) use a special ¼’’ presser foot for the sewing machine. This is a specialized sewing machine foot designed to guide the fabric at a consistent distance from the needle as you sew.

Keep in mind that even with a ¼’’ presser foot you will need to test the seam allowance and make adjustments first (as I explained in the how-to above). With my Janome, for example, I have to move the needle almost all the way to the right to get the SCANT ¼’’ seam allowance I need (because by default it sews a regular ¼’’ seam allowance).

But once you get the needle position right, the ¼’’ presser foot is super helpful in keeping that perfect distance at all times.

It’s important to note that the compatibility of presser feet can vary based on the sewing machine model, so it’s essential to ensure that the 1/4” presser foot you choose is compatible with your specific sewing machine. If you are unsure, consult your sewing machine’s manual or contact the manufacturer for guidance.

Other Tools for Getting an Accurate Seam Allowance

There are some other handy tools used to achieve the perfect seam allowance.

Quarter Inch Seam Guide

You can buy specialty acrylic seam guides that have the perfect needle position all figured out for you. A popular seam guide is the Perfect Piecing Seam Guide. It’s super easy to use. You just place the seam guide underneath the presser foot and then lower the needle into the hole in the seam guide. Then, lower the presser foot to hold the ruler in place. Mark the edge of the ruler with a piece of washi tape, and that’s your perfect scant ¼’’ distance.

There’s a great video that shows you exactly how it works here.

Magnetic Seam Guide

A magnetic seam guide is a small magnet with a groove that sticks to the metal needle plate of your sewing machine. Similar to a ¼’’ presser foot, it will help you keep your seams straight and on point.

Again, you will have to check the seam allowance distance first!

Washi Tape

Another cheap option is a piece of washi tape taped as a guide to your sewing machine. You can use any kind of tape (that you know you’ll be able to remove later) and tape it down at the measured distance form the needle.

They even make special ¼’’ seam tape, that has the ¼’’ markings printed on the tape, like this Diagonal Seam Tape. Super handy!

That’s it, friend! I think you know everything there is to know about the scant ¼’’ seam allowance. It might sound scary, but it really isn’t. And with these tips, I know you’ll be a piecing pro in no time!

Scant Quarter Inch Seam Allowance FAQ