Pinwheel Block

A Pinwheel block is made up of 4 Half-Square Triangle units laid out in order where all of the “blades” of the pinwheel seem to be twirling in the same direction.

Notice the two pinwheels below. The one on top appears to be “twirling” towards the right.

The one on the bottom appears to be twirling to the left.

It doesn’t matter which direction they are twirling. Just know that it can make a difference in the overall design, so you might want to make one block and keep it by your sewing machine so that your blocks will be consistent.

In order to make a pinwheel block, you need four Half-Square Triangle (HST) units. If you don’t know how to make them, check out my Half-Square Triangle Unit tutorial.

Once you’ve made four HST’s, lay them out as in the photo below. Two on top. Two below.

For this tutorial, I’ll refer to them as A and B (on top). And, C and D (on bottom).

Lay unit B, right-side down onto unit A. Just fold it over, right to left.

In the same way, lay unit D onto unit C.

Place a pin or two in the right side of each pair. This will help you to not get them turned around on the way to the sewing machine. In fact, I put a pin in the right side before I ever pick a pair up to align the raw edges to be pinned. I have sewn the wrong edges together and had to pick them out later. I have other things to do besides pick out stitches!

I usually just put one pin in the right side then stack them and take the stack to my sewing machine. When I pick up the top pair, the pin tells me which two edges to align and pin before putting them under the presser foot.


You can have several pinwheels stacked to take to the sewing machine. Just remember to always stack them “top-on-top”. The top pair in the pinwheel should be stacked on top of the bottom pair so that as you feed the pairs into the sewing machine, one after the other, they will always be in the correct order for final assembly.

Sew the top pair together, but DO NOT cut the thread.  Feed the bottom pair in and sew to the end.

Cut only the thread AFTER the bottom pair.  Leave the threads holding the two pairs together. This will ensure that your pinwheel does not get sewn wrong. Done that, too! I hate picking out stitches!

Take the pairs to the ironing board and press the seams to relax the stitches.

Open up the pairs and press the seam for pair A/B towards A. Press the seam for pair C/D towards D.

Fold A/B down over C/D.

Pressing the seams in opposite directions will let them snuggle right together.


Pinch them together firmly. You can feel when they lock together just right.


I place a pin to the left and to the right of the intersecting seam. Then, I align the ends and pin them and add another pin or two along the edge just to keep everything in place.

Take the block to the sewing machine and sew the pinned seam. I sew up to the pin, then hand-walk the needle over the pin to the seam before I remove the first intersection pin.

Before pressing your block, take a seam ripper and pick out the two or three stitches in the seam allowance.

Do this on both sides of the seam allowance.

Take the block to the ironing board, open it up, and lay it flat, wrong-side down on the board.

Push the seam allowances in opposite directions to open up the center seam. Press the center down with your finger.

Press the seams in the direction that you pushed them.

Then, press the center. It makes a tiny pinwheel.

Turn the pinwheel over and press it on the right-side of the block.

Now, on to the next one! 🙂