Those Dreaded Dog Ears!

No matter how many triangles you have sewn, when faced with determining the correct size of a dog ear, are you still unsure how much of an overhang there should be?  I hope to take some of the mystery out of dog ears, and once you know the reasoning behind the mystery, hopefully you will no longer feel confused. 

half square triangles

Dog ears are those little bits of fabric that hang over the edge after sewing triangles.  The most basic comes from sewing 2 half-square triangles together.  You start with two same-sized triangles, sew along the long (bias) edge with a ¼” seam, matching the beginning and ending points.

Half-squareAfter pressing, you get a square with small triangles hanging off 2 sides.  Just trim the overhang off even with the sides of the newly created square.  I use a small pair of scissors which are always sitting to the right of my sewing machine for easy grabbing.

Let me interupt for a moment to clarify – when I say 1/4″ seam allowance, I really mean a scant 1/4″ seam allowance.  This is just 2 or 3 fibers of fabric less than a full quarter.  I’ve also explained this in the introductory pages of the Nature’s Jewels pattern.

The next type of dog ear is created when you sew a triangle onto another piece where the end result is a smooth continuous line.  Here’s one example – when you sew this red triangle onto the blue shape (a trapezoid which started out as a rectangle, with two corners trimmed off on a 45° angle).  These shapes are used in the plum and blue diamond border in Part 7 of Nature’s Jewels.


After they are sewn, the outside edges will form a smooth uninterrupted line.  To achieve this, the size of the dog ear becomes important.  I like to place a straight pin over the two pieces simulating where the ¼” seam allowance will be – as if it was the thread.  The pin should hit just where at the crux of the 2 triangles.

Place pin along seamline

When you sew on the seamline, the thread will also hit right at the crux.  (I used contrasting thread for better visibility.)

Aim for crux

And after you press toward the triangle, trim the dog ears and you will have a straight edge on both sides of the triangle.  This tells you that you estimated the size of the dog ear successfully!

Trim dog ear; get straight edge

Another type of triangle/dogear is when you sew a triangle (or 2) to another triangle, like in a Flying Geese unit.  The important thing here is that when you then sew the Flying Geese unit to the next piece, you don’t cut off the tip of the center triangle.  And that is all dependent on having the correct size of dog ears.  There’s basic geometry involved here but I won’t bore you with the details!

The next set of photos will walk through this process.  These are the 3 triangles that make up one Flying Geese unit (or Flying Goose as my friend likes to say – that is just WRONG!)

 Parts of a Flying Geese unit

Place the right blue triangle over the red, right sides together. 

Right sides togetherBut this is not the way you’ll want to position it for sewing – it’s awkward to start at the crux.  So flip the pieces over so the red triangle is on top.

Position this way

Match the starting triangle points and pin if you prefer.  It’s the ending position that creates the dog ear we are concerned with.  Unlike the situations described above, in this case we want a dog ear that is bigger than you think it should be.  The seam should NOT meet at the crux, but before the crux.  I use a fine straight pin to simulate the 1/4″ seam, and make sure the dog ear is bigger as shown below.

Use pin to simulate seamThen place the pin just before the important crux, taking just a little fabric so it can’t shift over the pin.  You’ll sew almost right up to the pin so the top triangle doesn’t shift.

Pin placement

This is what the seam will look like.

Larger than you think

So you can see that the seam didn’t hit at the crux.  When pressed (toward the smaller triangle), you’ll see that the dog ear extends beyond the red triangle.  Do not trim the dog ear as you will use it as a reference for the next step.

A little extra

Next, place the 2nd blue triangle on top (rights sides together), aiming to have the same size dog ear as the first (think German shepherd).

Same size dog ear

This time, you will sew to the crux.  I could have done a teeny bit better job in my sample, but it is close enough to not fret about.  Hear’s how it looks sewn:

Aim for the crux.

The dog ears look to be about the same size.  That will give you a smooth edge across the top when pressed.

Flat across top

Having this extra-big dog ear will ensure that when you sew the Flying Geese to the next piece, you can take a 1/4″ seam allowance and not cut off the peak of the red triangle.  There’s nothing more obvious than blunt-tipped triangles!

Quarter inch for next seam

Quarter inch without cutting off tip of triangle

Then when you’re done, trim the dog ears even with the sides of the newly formed rectangle.  In certain cases I like to leave the double-dog ear until I’ve sewn the next seam, as a reminder that I need to pay attention at that exact point to not cut off the tip of the triangle.  After I sew the seam, then I trim the dog ear.

Trim the Dog earss.

This is the exact same size dog ear you would use when making a square-in-a-square unit.

Parts of square-in-a-square unit

First sew the red triangles to opposite sides of the square, keeping the non-bias square on top while sewing.  The dog ears should be of the extra big type as shown in the Flying Geese unit.

Sew 2 triangles

Press toward the triangle – do not trim the dog ears!  Next place, pin and sew the 2 blue triangles to the unit, making the dog ears the same size as the red ones.  Stitch aiming for the crux.

Double dog ears

Press toward the triangles and you should have a smooth, straight edge on each side of the new square.  Trim the dog ears even with the edges of the square.

Straight line when pressed

There may be other instances where dog ear size varies, but these are the most common.  Do take the time to use the straight pin to simulate the 1/4″ seam.  After doing that a few dozen times, you’ll be able to judge by sight without the pin.


About laurieshifrin

I am a quilt designer, author, quilting teacher and lecturer.
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