Half Rectangle Triangles - Easiest Tutorial to Make Them

Learn how to make half rectangle triangles for your quilting projects. A quilt that needs rectangular shapes in its design, made up of contrasting triangles, will need you to master these quilt blocks. Half rectangle triangle is usually written as HRT in quilting jargon. It is an elongated version of a half-square triangle.

Half Rectangle Triangles Tutorial

When making half rectangle triangles, it is easy to think that they are almost the same as half square triangles, but they are not. They have to be made up differently since they don't have equal sides.

One of the most important differences is that the orientation of the rectangle is very important. This is because they are not symmetrical, so are not interchangeable. The direction of your diagonal cut is very important here.

Half Rectangle Triangles - Supplies

If you are trying to make these for the first time, it is a good idea to have a practice run with some scraps first so you can get the feeling of making them. You don’t want to waste your best quilting fabric on experimental blocks!

• Fabric - Quilting fabric or tightly woven cotton fabric in colors of your choice.
• Thread - Strong thread suitable for quilting
• Pen - Removable marking pen.
• Quilting Ruler- Preferably one with ¼” markings on the corners.
• Sewing Machine
• Cutting Mat and Rotary Cutter- Be sure your rotary cutter is sharp. Replacement blades are available.
• Optional- Acrylic ruler/stencil made, especially for half-square rectangles.

How To Make Half Rectangle Triangles

If your chosen quilt design contains these shapes, here are the best ways to make them:

Method 1 - One at a Time

The first method sews one half rectangle triangle at a time however, you will get 2 half rectangle triangles from two rectangles of fabric.

Cut two rectangles of the size you require (plus seam allowance) in contrasting fabrics.

Draw a diagonal line from corner to corner on each rectangle. Notice how the diagonal lines in both of my fabrics are facing the same direction.

Cut along your diagonal lines.

Arrange your triangles so they are with their contrasting fabric.

Put the triangle pieces right sides together and sew your seam with a ¼” (6mm) seam allowance. You will see that the direction of your diagonal line makes a big difference in the orientation of your final rectangle. You will need to calculate beforehand which orientation you need to suit the pattern you want on your quilt top.

Be sure to place the triangles as pictured (see the triangles are not matching on the edges). If you line them up incorrectly, you will end up with kite shapes instead of rectangles!

Press the seam allowance towards the darker fabric and trim. There is a separate section lower down in this tutorial on how to trim the half rectangle triangles.

Although this method takes a bit more time, as you are only creating one rectangle at a time, you have more control over the direction of your triangles. You can then lay them out to make up your quilt top as you make them. Mix and match each rectangle as you need them! It is a bit more fussy, but you have less chance of making mistakes!

Method 2 - Two at a TIme

This method of making half rectangle triangles is more similar to the way you make half square triangles. It will make two rectangles at a time.

Cut two rectangles from contrasting fabrics.

Line up your contrasting rectangles on top of each other with right sides together. Now rotate the top rectangle as shown. The corners must match up, as shown in the picture.

Draw your diagonal line with a removable marker.

Sew ¼” (6mm) seam on both sides of the line.

Cut along the line, open out and press, with your seam towards the darker side.

You will now have two half rectangle triangles. Trim according to the section below.

Their orientation will be in opposite directions, so you can only use this method if that will work with your quilt top.

Method 3 - Using Templates

The last way to make half rectangle triangles is to use a pre-purchased acrylic ruler, specifically made for this purpose. It is a triangle-shaped stencil, with all the ratios and angles already worked out for you.

This takes most of the calculation work out of creating these shapes. You simply use the stencil to draw the shape onto your fabric, then cut each triangle out separately before joining them to form the rectangle. This definitely takes more time than the other methods, but it can be more accurate, and you have much less chance of making mistakes with orientation.

Trimming your Half Rectangle Triangles

Trimming is essential for this shape for two reasons: They distort easily because of the bias of the triangle, and it is easy to ‘lose’ that little extra along your diagonal seam to give you the seam allowance to sew your rectangles together. When your rectangles are joined, you want to have perfect points at the corners!

For this, it is helpful to have a quilting ruler which shows a ¼” (6mm) square in the corners. If your ruler does not have this, either place some tape ¼”(6mm) away from the edges in the corners, in a right angle shape. Or alternatively, draw a dot where the ¼” (6mm) lines would intersect, with a permanent marker.

Now line up your ruler on top of your rectangle so that the ¼” by ¼” intersection is exactly over your diagonal seam line, or your marked dot.

Trim the long side of your rectangle first. Make sure your fabric is completely straight, not at all angled. Do this by lining it up with the lines on your cutting mat. After the side is trimmed, you can trim the top.

Now rotate the rectangle by 180 degrees and do exactly the same with the other corner.

You will see that the seam line does not reach the exact corner of your rectangle. This is correct. You will need that little extra ¼” to form the seam allowance for sewing the rectangles together.

When you have completed these trims, check if you still have any dog ears, and trim them off too.

Sizing of Half Rectangle Triangles

The easiest formula for working out the size of your half rectangle triangles is to be sure the measurements are in a 2:1 ratio. This means that the length is twice as long as the width. If you have longer, thinner rectangles, they will be more difficult to trim. 

Here is a table to help you work out the cutting sizes for your quilt.

Cut Rectangles	Trim Size	Finished Size
2”x 4” (5 x10cm)	1-½”x 2-½”(3.8 x6.3 cm)	1”x2”(2.5x 5 cm)
2-½”x 5”(3.8x 13cm)	2”x 3-½”(2.5x 9cm)	1-½”x 3”(3.8 x7.6 cm)
3”x 6”(7.6x 15 cm)	2-½”x 4-½”(3.8x 11.4 cm)	2” x 4”(5 x10cm)
3 ½” x7”(9 x18 cm)	3”x 5-½”(7.6x 15 cm)	2-½” x 5”(3.8x 13cm)
4” x 8”(10 x20 cm)	3-½” x 6-½”(9x 16.5 cm)	3”x 6”(7.6 x15 cm)
4-½” x 9”(11.4 x23 cm)	4” x 7-½”(10x 19 cm)	3-½” x 7”(9 x18 cm)
5” x 10”(13x25cm)	4-½” x 8-½”(11.4x 21.6cm)	4” x 8 “(10 x20cm)

Please note that cm conversions have been rounded off, and are not as accurate as the inch measurements!

If you require different sizes to those mentioned here, the formula for cutting size is this: Length= finished size + 2” and Width= finished size +1”

If you decide that you absolutely must have long, thin rectangles for your particular design, (not in the 1:2 ratio), the best plan is to still use the 1:2 ratio, but make a test rectangle first. You will see that you have to trim quite a bit off it. If your block is too long when you trim it, make it shorter and try again.

What Can I Do With These Half Rectangle Triangles?

Once all your half rectangle triangles are trimmed, you can arrange them to make up your quilt top. Experiment with various designs while they are still separate so that you can find the most visually pleasing arrangement.

If you have constructed and trimmed your HRT’s carefully, they will join together beautifully, with perfect points. Once you combine your rectangles in different orientations, you can make many different patterns. If you combine them with a few squares and half square triangles, you can make even more! Here are some examples:

Half Rectangle Triangles - In Conclusion

Now that you have mastered the art of sewing half rectangle triangles, you can generate a whole lot of new quilt designs using them as your basic units! They are not quite as versatile as half square triangles, but they can make some interesting designs!