How to Make a Pinwheel Quilt Block, and a Free Pinwheel Quilt Pattern

Four half square triangles. That is the entire Pinwheel quilt block.

Quilters write that unit as HST, and this tutorial uses both names, because every pattern you meet will use one or the other.

No plain squares, no templates, no set in seams, and nothing to line up except four seams that meet in the middle. It is the block to make the day after you learn half square triangles, and it is the reason so many quilters learn them in the first place.

What follows is the whole thing. What the block is, what to cut for six sizes, the one trick that makes the center lie flat, what happens when the blocks sit side by side, and how many you need for a pinwheel quilt. There is a free pinwheel quilt pattern sheet near the end, and you do not have to hand over an email address to get it.

What the Pinwheel quilt block is

Four HSTs in a two by two grid. Every one of them is a half square triangle, and every one is turned a quarter turn from the one before it. That rotation is the whole design. Place the four of them symmetrically instead and you get bars or a large triangle; turn each one a quarter turn and the block spins.

In the language of quilt blocks this is a four patch. Four patch blocks are made of four units in a two by two grid, and along with nine patch blocks they are the backbone of an enormous number of quilt designs. Each unit here finishes at exactly half the block, so a 12 inch Pinwheel is four 6 inch units and an 8 inch Pinwheel is four 4 inch units. Any even number works, which is why this block scales so easily.

The HST is the only unit in it. You will also see that unit called a pieced triangle square, a two triangle square, a split square or a bias square, all names for the same thing: a square made of two triangles meeting on the diagonal. Four HSTs, arranged so they spin, is the traditional Pinwheel block in full.

The name has a date. Barbara Brackman records that the block was given the name Pinwheel by Ruth Finley in 1929. You will also meet the same arrangement called a Windmill, which is the name a good many shops and patterns use for it, and the Windmill block you find under that name is usually this one. Like most old block names, Pinwheel has been attached to more than one arrangement over the years, so if a pattern calls something a Pinwheel and the picture does not match this one, trust the picture.

The Pinwheel cutting chart: the common Pinwheel block sizes

The fabric requirements could not be smaller. Two fabrics, one light and one dark, and four squares in total.

A is the four squares you start with for the two at a time method, two light and two dark, which yields all four HSTs. The next column is the alternative: one light square and one dark square at that size give four units at once by the four at a time method. Every number in the cutting chart is in inches.

The formula behind the pinwheel quilt block size chart is short enough to keep in your head. Each HST finishes at half the finished Pinwheel block. Add 7/8 inch to that for the squares you cut, and trim each finished unit to the unit size plus 1/2 inch. The four at a time column is the trimmed unit size multiplied by 1.6, rounded up to the next quarter inch.

Cutting from precuts and yardage

A charm pack makes this block without a ruler doing any real work. Four 5 inch charm squares, two light and two dark, give an 8 inch finished Pinwheel: pair them, make the units two at a time, and trim to 4 1/2 inches. That is one block from four squares with nothing left over worth keeping.

A layer cake handles the 12 inch block. Cut one 6 7/8 inch square from each of four 10 inch squares, two light and two dark, and you have a 12 inch Pinwheel with a useful strip left from each.

Two fabrics is the traditional block, and a crisp white background behind a single strong print is the version that turns up most often. A white background is not the only choice, though: three colors work just as well here, one for the background and two that alternate as the dark half from block to block, and the quilt gains a rhythm without gaining a single extra seam.

Precuts suit the dark half of the block, where every pinwheel can happily take a different fabric. The background is the opposite case. It repeats across the whole quilt and it is what the pinwheels are read against, so it wants to come off one bolt from the first block to the last. That is a job for fabric by the yard rather than a bundle, and solids are what keep the shape crisp.

Fat quarters sit between the two, and they are the practical cut for a scrappy pinwheel quilt where every block gets its own fabric.

Making the four HSTs, step by step

Step one. Take two light and two dark squares at the A size, and pair one light square with one dark, right sides together. Draw a diagonal line on the wrong side of the light square, from one corner to the opposite corner.

Step two. Sew 1/4 inch either side of that drawn line, then cut on the drawn line. Two HSTs.

Step three. Set the seam, then press towards the darker fabric, opening the unit with your fingers first and moving the iron up the straight grain rather than along the diagonal, because that seam is on the bias and will stretch if you push it.

Repeat with the second pair, right sides together again, and you have all four HSTs. The books call this sandwich piecing, and it is the quickest honest route to a small number of them.

A word on pressing them. Towards the dark is the usual instruction, and it is what makes the seams nest later. Pressing the seams open is the other option, and it is worth knowing: seams open gives the flattest unit and the least bulk where four points meet, at the cost of the nesting that helps the rows line up. On a Pinwheel, where the middle is the whole problem, some quilters press every one of those seams open for exactly that reason. Either works, as long as you do the same thing to all four.

Step four is to trim. Every HST comes off the sewing machine a little oversized on purpose, and every one gets trimmed to the size in the last column before it goes anywhere near the block. Lay the 45 degree line of a square ruler along the diagonal seam, cut two sides, then rotate the ruler, realign it and cut the other two, and trim off the dog ears. Trim before assembly, never after. Squaring up a finished block does not rescue units that were never square, it just cuts the points off.

All three methods, and a printable size chart that covers every size in the table above, are in our guide to making half square triangles.

It is worth knowing the unit next door while you are here. Quarter square triangles are the other classic unit, one square split on both diagonals instead of once, and they have a size chart and three methods of their own. Flying geese are the other workhorse triangle unit, built from rectangles rather than squares, and they combine with these in a great many blocks. If you want them, we have flying geese four at a time written up as well.

One warning about the four at a time method here

Four at a time is tempting for this block, because four is exactly what it needs. It has a real cost, though. Fabric is woven with lengthwise warp threads and crosswise weft threads, and both of those are firm; at 45 degrees to them lies the bias, which has the least strength and the most stretch. Two at a time and the Magic Eight leave that bias inside the seam, so all four outer edges of the finished HST are on the straight grain. Four at a time puts the bias on all four outer edges instead.

In a Pinwheel every one of those bias edges ends up on the outside of the block, where nothing is holding it steady and where the next block will be sewn to it. The old rule is that when in doubt you want the straight grain on the edges, because bias edges distort and stretch with handling and pressing. On small HSTs four at a time is a fair trade for the speed. Above five or six inches it is a long run of bias to trust, and it is exactly the argument some quilters make against the method. If you use it for a large Pinwheel, handle them as little as possible and sew them into blocks as soon as they are trimmed.

Sewing the Pinwheel block together

Arrange the four HSTs before you sew anything, in a two by two grid with each one turned a quarter turn from the last, so the dark triangles chase each other around the middle. Then look at the layout rather than at the pieces. One unit turned the wrong way is the only real mistake this block makes, and it is obvious on the table and invisible under the presser foot.

Sew the top pair together and the bottom pair together with a 1/4 inch seam allowance, right sides together as always. Press the top seam one way and the bottom seam the other, so the two nest when the rows meet, or press both open if that is what you did to the HSTs. Then assemble the block: join the two rows, nesting that junction and pinning through the exact point where the seams cross, on both layers, so the needle passes through it.

The finished Pinwheel block should measure its finished size plus 1/2 inch, so a 12 inch Pinwheel comes off the machine at 12 1/2 inches square.

Spinning the center seam

This is the one thing that separates a flat Pinwheel from a lumpy one, and it takes about ten seconds.

Four seams meet in the middle of this block. Press that last long seam to one side in the ordinary way and all of those layers stack in the same place, so the center of the block sits up in a small hard knot. Quilting over it later is unpleasant, and the block will not lie flat next to its neighbours.

Instead, spin the seam. Turn the block over, find the two or three stitches that run through the seam allowance itself at the very center, and unpick them as far as the stitching line and no further. The seam allowances are then free to turn. Press so they fan around the center, each one lying in the opposite direction to the one across from it, and a tiny four patch of allowances appears in the middle. The center flattens out, and the bulk is shared between four places instead of piled in one.

It is the same trick that flattens a four patch or a nine patch, and it is worth learning here where the result is so easy to see. Our guide to getting quilt points to match covers it alongside the pinning that goes with it.

Where Pinwheel points go wrong

The tip of each triangle sits exactly 1/4 inch in from the raw edge, and a Pinwheel has four of them meeting at one spot. There is no margin in that number.

Trim every HST to size before assembly, not the block afterwards. An HST an eighth of an inch small has nowhere to hide next to three that are not.

Keep one seam allowance for the whole block. Most teachers of patchwork ask for a scant 1/4 inch rather than an exact one, to allow for the thickness of the thread and the small amount the fabric takes up when the seam is pressed to one side. A consistent scant 1/4 inch beats an inconsistent exact one every time.

Pin through the seam junction itself, through both layers, rather than beside it. The pin holds the point where it needs to be while the feed dogs try to move it.

And look at the blade before a stack of them. A blade that has gone dull stops slicing and starts dragging, and the layers shift a fraction under the ruler without you feeling it happen. A fresh rotary blade costs less than the fabric you lose recutting pieces that were never square. A square ruler in your unit size is the other thing worth owning, because trimming four of them in four single cuts is a different job from trimming them in eight.

What happens when the pinwheel blocks sit side by side

A single Pinwheel is a pleasant thing. A field of pinwheel blocks is a different one, because the corners of four of them meet and the eye starts joining triangles across the seams.

Set every block spinning the same way and the quilt reads as a regular field of turning shapes, calm and even, the pinwheel effect repeating evenly across the top. Alternate the direction, one clockwise and the next counter clockwise, and new shapes appear at each junction where four Pinwheel blocks meet, shapes that are in none of the blocks themselves. Neither takes any extra piecing. It is the same easy block, arranged differently.

This is the reason to arrange the whole quilt top before joining any of it, on a design wall or on the floor, and to look at it from across the room rather than up close.

Pinwheel quilt block variations

The half square triangle is the most rearrangeable unit in patchwork, and the Pinwheel is where that becomes obvious. Take the same four units and put them down differently and the block changes name: the simple Pinwheel block, once rearranged, becomes Broken Dishes, Barn Raising, Streak o' Lightning and many more. Nothing about the cutting changes.

Beyond the rearrangements, a few pinwheel quilt block variations that need no new technique and no change to the instructions above:

Scrappy pinwheels. The same background in every one of the pinwheel blocks, a different dark in each. This is the friendliest way to use a scrap basket, and holding the background steady is what makes a scrappy quilt hang together rather than look like a jumble. Scraps as small as a charm square are enough.

Two colour pinwheels. The same light and the same dark across the whole quilt. Severe, graphic, and very hard to beat in solids.

Double pinwheel. Replace each half square triangle with a unit made of two triangles of different value, and the block reads as two pinwheels turning inside each other. Designers publish more than one thing under the name Double Pinwheel, so check the diagram before you cut.

Pinwheel star. Put the pinwheel in the center of a larger star block instead of a plain square, so the star points frame a spinning middle. The Friendship Star and the Ohio Star both have a plain center square that a small pinwheel will drop straight into, as long as it finishes at the same size.

Disappearing pinwheel. Sew the block, then cut it apart and rearrange the pieces into something that no longer looks like a pinwheel at all. It is a whole family of blocks built on this one, and the block you start with is exactly the block above.

Turning it into a pinwheel quilt

The math is friendly because the block sizes are even numbers.

Thirty 8 inch pinwheel blocks set five across and six down give a pinwheel quilt top of 40 by 48 inches, a good baby quilt or a small lap quilt, and thirty blocks is only one hundred and twenty HSTs. Twenty 12 inch blocks set four by five give 48 by 60 inches, a proper throw. Twelve 8 inch blocks, three by four, make a 24 by 32 inch panel or a small pinwheel baby quilt. If you would rather work back from a bed, our quilt size chart has the sizes to aim at.

Add a border and every one of those numbers grows by twice the border width, so it is worth deciding on the border before you decide how many blocks to make rather than after. A 4 inch border turns that 48 by 60 throw into 56 by 68.

Sashing between the pinwheel blocks separates them so each one is read on its own, and it adds finished size for every strip you put in. Sashing is also called lattice or setting strips, and adding a small setting square where the strips cross turns the sashing itself into part of the design. Leaving the sashing out is the opposite choice and the more interesting one, because it is the blocks touching that makes the secondary shapes appear.

Turning the pinwheel blocks 45 degrees gives an on point setting, which changes the quilt completely without changing a single block. It needs corner triangles and side triangles to bring the edges back to a straight line, and those are cut to a formula rather than guessed at: our guide to setting a quilt on point has both.

One quilting note. A block that spins asks to be quilted in a way that agrees with it. A linear pattern will accentuate the shape of the block, while curved lines and spirals suggest movement in a way that straight lines do not. And the space created by the junction of four blocks allows for further quilting, which is where a small motif of its own usually belongs.

The free pinwheel quilt pattern sheet

Everything above fits on one page, and we have put it there so you can keep it next to the machine instead of scrolling on a phone with pins in your hand.

The sheet has the block diagram, the cutting chart for all six sizes, the two at a time method step by step, the layout and pressing instructions, how to spin the center seam, and the quilt sizes. It prints on letter or A4 and nothing on it needs to print at actual size, because this block has no templates.

Everything in this tutorial is on it. The downloadable PDF is here: the Pinwheel quilt block pattern sheet. It is free to print, use and teach.

Pinwheel questions we are asked most

What size squares do I need for a 12 inch Pinwheel quilt block?

Four squares at 6 7/8 inches, two light and two dark. Pair them right sides together, make the four HSTs two at a time, trim each to 6 1/2 inches, and the block comes together at 12 1/2 inches square.

How many half square triangles are in a Pinwheel block?

Four HSTs, and nothing else. That is the whole block, which is why it is the fastest classic block there is.

Is there a free printable pinwheel quilt pattern?

There is one in the section above, a downloadable PDF, and the pattern costs nothing. What it will not contain is templates to cut around, because there are none in this block. Every piece is a square cut with a rotary cutter, so what you actually need is the cutting chart, and that prints at any scale you like.

Why does the center of my Pinwheel block stick up?

Because four seams are stacked in one place. Spin the center seam: unpick the two or three stitches through the seam allowance at the very center, then press the allowances so they fan around the middle instead of piling on one side. The section above shows the back of the block both ways.

Is the Pinwheel good for a beginner?

It is one of the best first blocks with triangles in it, and one of the easiest. No curves, no set in seams, no templates, no plain squares to keep track of, and only one skill to learn, which is the HST. If that unit is new, start with how to make half square triangles and come straight back. If quilting itself is new, our complete beginner guide to making a quilt starts at cutting and carries on to binding.

What is the difference between a Pinwheel and a Friendship Star?

Size of grid, mostly. A Pinwheel is a four patch, two by two, made only of half square triangle units. A Friendship Star is a nine patch, three by three, with four HSTs on the sides, four background squares in the corners and a plain center square. The Pinwheel is the simpler of the two and a sensible block to make first.

Can I make a Pinwheel from a charm pack?

Yes. Four 5 inch charm squares, two light and two dark, give one 8 inch finished Pinwheel. Trim the units to 4 1/2 inches before you sew them together.

Where does the name come from?

Barbara Brackman records that the name Pinwheel was given to the block by Ruth Finley in 1929. The arrangement itself is far older than the name, as spinning four triangles is about the first thing anyone does with a pile of them.

What to have ready

• A light and a dark quilting cotton, or four squares from a charm pack for an 8 inch block. Solids keep the shape crisp.
• A rotary cutter with a sharp blade, a mat, and a square ruler in your unit size for trimming.
• Something that keeps the 1/4 inch honest on every seam, such as our seam guide ruler.
• A marking pen or pencil for the diagonal line, pins, and a seam ripper for spinning the center seam, all in notions.
• An iron, and the patience to press rather than push.
• The pattern sheet above, printed.

Where to start with your first Pinwheel block

Do not plan the next quilt yet. Cut four squares at 4 7/8 inches, two light and two dark, and create one 8 inch Pinwheel quilt block. Make them two at a time, trim to 4 1/2 inches, sew the two pairs, assemble the block, and spin the center seam. It is a half hour project, start to finish.

Then put it on the table and turn it on the table until you can see why the direction matters. Then make three more and set the four pinwheel blocks together, first all spinning the same way, then alternating. You will decide what your quilt looks like in about a minute, and you will have learned this tutorial by heart by then.

Marbelia Fernandes
The Fabric Hut Co-Founder

P.S. If the center of your first one sticks up, do not unpick the whole block. Unpick three stitches at the middle and press again. It is nearly always that.