If there’s ever anything guaranteed to get people’s knickers in a twist in the quilting world, it’s the concept of the 1/4″ seam, scant or otherwise. In all areas of sewing a seam allowance is the bit of fabric between the stitching line and the edge of the fabric. It is not usually seen in the finished article, but is there to stop the thread holding the pieces together pulling through the edge of the fabric and unravelling everything.

In quilting a seemingly innocuous 1/4″ seam is standard for most patterns (unless you live in one of those strange countries that uses metric, but I’m sure they have a 5 mm or 7.5 mm seam problem!), however achieving this causes no end of headaches, to beginners especially.

So what’s the problem?

Well here’s the bit that people forget when measuring, cutting and sewing their pieces:

  • When the dimensions of a piece in a quilt/block are measured, 1/4″ is added onto each side of the required ‘finished’ piece, so a piece finishing at 3″ x 3″ would be cut at 3 1/2″ x 3 1/2″
  • When two pieces are sewn together, in order to get the block/quilt to lie flat, both pieces must be folded away from the stitching line regardless of whether you choose to press your seams open or to the side
  • The stitching line will always take up a thread’s width on each piece
  • The fold will always take up a fraction of an inch whether split equally between both pieces if the seam is pressed open, or being taken up entirely on the piece that the seam allowance is pressed towards if the seam is pressed to the side
  • Since the original measurements require a certain finished size, both the thread width and fold must be taken up within the seam allowance otherwise your finished size will be too small
  • Any inaccuracies will be magnified if you have drawn on a sewing line using a 1/4″ ruler, since the ruler is taking up your 1/4″ and any line will actually be a fraction to the right of where your stitching line should be, so you will not only have the thread width and the fold width to contend with but the width of your marking tool as well (which is why, when using the method to make HSTs using 2 squares at a time with the line drawn on the diagonal, the required square sizes are generally rounded up by 1/8″ to a neat full inch or half inch measurement, as the stitching is normally done either side of a drawn line and the final blocks trimmed to size)

Want to test it out yourself?

Get two scraps cut at 3 1/2″ x 3 1/2″, then on the back of one draw a line 1/4″ in from one side.

Place both squares right sides together and stitch them together along the line you drew, then open them back out again and press.

Measure the width of the two joined pieces – for a quilt block it would need to be 6 1/2″, but I bet you’ll find it’s smaller than that by somewhere between 1/16″ and 1/8″.

Let’s look a little closer at how short that actually is:

Oh dear, nearly 1/8″ off!  On its own that doesn’t seem like a massive amount, but the more you join together, the more you lose, and if you’re piecing complex blocks with many pieces you will soon find yourself coming to grief trying to join different units together, such as adding 2 joined HSTs to a solid rectangle, as your rectangle will be slightly bigger.

How do you combat this?

This is where the concept of a ‘scant’ 1/4″ seam comes about, because in order to accommodate the thread line, fold and possibly drawn line, you can’t start out with your needle 1/4″ away from the edge of the fabric, it needs to be just under the 1/4″.

How you choose to deal with the measuring of the distance between the needle and the edge of the fabric is entirely up to you – there are a variety of 1/4″ feet, some better than others, and some more prone to being knocked off kilter than others (my Brother one with a blade guide attached to the side was measuring about 3/8″ out of the box, so it stayed in the box). There are also ‘standard’ feet for machines that have 1/4″ marked on them, or are 1/4″ to the edge based on the needle being in a certain position. If you don’t fancy trusting either of them, then there are also seam guides, but you will need a narrow foot to be able to use one of them for a 1/4″ seam (seam guides are particularly suited to vintage Singers where the right hand edge of the standard foot is only 1/8″ from the needle)

Whichever option you choose, you will need to carry out some experiments to get things precise – remember also that how you press your seams will make a slight difference, so re-measure if you are switching from one to the other.

Here’s another pair of 3 1/2″ squares that I sewed using my chosen scant 1/4″ method:

A bit closer:

Remember that whatever you choose it has to be repeatable if your setup changes, eg your needle moves when you turn the machine off, or you have to remove the seam guide to make something else, so make notes of whatever you did, and once you hit on a method, repeat a few times to be sure that you’re getting consistent results.

Will it be the end of the world if I just leave it?

That depends on where your sewing is going!  If you only ever make quilts for yourself or others and don’t mind losing points on triangles or things turning out a bit smaller than intended, then that’s perfectly okay. If you’re just doing simple patchwork with squares, no-one will ever even know unless they dig out a ruler, and if they do then you can feel perfectly entitled to give them a smack upside the head for sticking their nose in where it’s not wanted.

However, if you’re contributing pieces to a bee quilt or a charity quilt drive, it becomes much more important.  It’s very difficult if you find yourself faced with a set of blocks that range between, say, 12 1/4″ and 12 3/4″ (because people can also go too big by erring on the side of caution and being a bit too scant), since it’s not a simple matter to join them together, and depending on the pattern it’s usually not simple to just trim to the same size, because then you’re likely to lose important bits.  Think of the poor people assembling those quilts, and try to be as accurate as possible.