How to trim quilt blocks

A perfectly trimmed quilt block
A perfectly trimmed quilt block

The perfect quilt starts with the perfect quilt block, and I’m going to show you how to trim quilt blocks so they join together beautifully. This is the method I used in my Tulip applique quilt, and I recommend it for any quilt blocks, whether you make them by hand, freestyle on your sewing machine or in the hoop on your embroidery machine like I do.

Once you’ve finished your beautiful quilt blocks they are going to need some trimming before you join them together. No matter how carefully you cut your fabric and hooped it, the process of embroidering will distort your piece to some extent. Trimming your blocks means that your quilt will sew together square and true and accurate. Everyone wants that. So I start big and trim down.

  • I stitch my blocks with plenty of spare fabric so I can trim accurately.
  • I decided it’s worth sacrificing the extra for a perfectly trimmed block
  • I wasted more fabric trying to work with skimpy allowances
  • It’s a lot easier to join the blocks with generous seam allowances

I admit it took me a while to get over the idea of wasting all those offcuts. But that’s a lot easier to deal with than the time I embroidered a whole set of blocks with seam allowances pre-cut to the right size….and had to start again once I realised they would be too small after I trimmed them. Those babies will get used in another project, but I won’t be making that mistake again.

If you’ve used one of my in-the-hoop designs you will have made a quilt block that looks something like this when you take it out of the hoop:


Completed block before trimming

We need to get that beauty in shape, ready to join together. Now, when you follow the instructions in one of my quilt block designs, you’ll see I cut my fabric with a generous allowance. This means we can trim each block down to an accurate size with perfectly square corners. It’s extremely important to be accurate when piecing and this method practically guarantees your blocks will join trouble-free.

The basting line on the finished block makes a handy guide for trimming. I design all my blocks to have a 1″ allowance after trimming.

Note: If you have used a fusible batting or foam stabiliser (eg Bonsal), DO NOT press your block until the blocks are sewn together. 

Take your ruler and align the 1″ line with the basting stitch along one side of the block. You can see the green basting lines in this picture:


We’re going to use the basting lines as a guide

When you have the ruler correctly aligned, the stitches should be hidden by the line on the ruler, like this:

Align the 1″ mark on the ruler with the basting stitch.

The basting line might not be perfectly straight, as the embroidery and applique process tends to pull the fabric in towards the centre of the block (which is why we need to trim and square it). If your basting is out of alignment like mine was, line up the ruler with each end of the stitching. The centre of the stitching might show below the line, but don’t worry about that.

You can just see in this picture that the pink basting stitch appears below the 8-9-10 marks on my ruler. This is OK.

Align your ruler with the ends of the line.

Use your rotary cutter to trim along the edge of the ruler. Trim through all layers; top fabric, stabiliser, batting and backing or lining.

You should now have a quilt block with a perfect 1″ seam allowance along one side.

Trim along the edge of the block

Now we are going to use the edge you just trimmed together with the basting stitch to get a perfect 90 degree corner.

Rotate your block 90 degrees, so the trimmed edge is at the side, like this:

Rotate the block so your trimmed edge is at the side

Place the ruler on the quilt block as before, but this time make sure the vertical markings on the ruler align with the trimmed edge of the block. You can see the cut edge lines up with one 1″ mark and the basting stitch lines up with the next.

Line the short side of the ruler with the trimmed side

Now line up the 1″ mark on the horizontal edge of your ruler, matching it to the basting stitch just like before. This time we will keep that vertical alignment too, so that when you trim you have a perfectly square corner.

Line the long edge with the basting stitch as before

Keep turning and trimming, aligning the verticals and horizontals as you go, and you should end up with a perfectly trimmed quilt block that looks like this:

The trimmed block ready for joining

As a final check, make sure that all your blocks are the exact same size. If any of them are a little larger, carefully trim the extra.

Still bothered by those offcuts? You could save the batting scraps to stuff toys or in-the-hoop felties. Little fabric trimmings are ideal for stuffing pincushions. And I join my stabiliser offcuts to reuse.

Ready to join your blocks together? I show you how in the next post: How to join your quilt blocks.

Technique: quilt as you go

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2 thoughts on “How to trim quilt blocks

  1. Dyann says:

    I’m making the tulip quilt blocks
    When do I tear away the stabilizer ?
    You say to use tear away
    Stabilize but wondering if wash away would make more sense

    • Lisa says:

      Hi Dyann, I prefer to use a polymesh stabiliser and leave it in (you can see it in the photos) but if you’re using tear-away you can leave it in until you’ve finished the block and tear it away from the outside edge.
      I tend to hoop the stabiliser, stitch the block and leave the stabiliser in. It gets trimmed off after the blocks are done.
      I guess you could use washaway, but that’s quite an expensive option. Plus it tends to leave your work a bit stiff unless you rinse really well.

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