How to Knit a Mitered Square Blanket – Free Tutorial

There is something deeply satisfying about a mitered square blanket. Each square is its own small accomplishment, worked from the outside edges toward a center point, and when you sew them all together, the diagonal lines create a geometric rhythm that looks far more complicated than it actually is. This is one of those projects that travels well, works up quickly once you get the rhythm, and uses up yarn from your stash in the most gratifying way possible. Whether you are a confident beginner or an experienced knitter looking for a meditative, manageable project, this tutorial will walk you through every step of making your own mitered square blanket from scratch.

Let’s get into it.

What Is a Mitered Square?

Before we dive into the how-to, it helps to understand what makes a mitered square different from a regular knitted square. In standard square knitting, you cast on a number of stitches and work straight rows until the piece is as long as it is wide. Simple enough.

A mitered square works differently. You cast on stitches along two sides of the square — essentially casting on twice the number you’d normally use — and then you decrease at the center on every right-side row. Those decreases pull the fabric inward toward a diagonal center line, creating a square that sits on point, like a diamond. The decreases are the “miter,” and they give the fabric its characteristic folded, geometric look.

When you join multiple mitered squares together, those diagonal lines align in endlessly satisfying ways. You can arrange the squares so the center lines all run in the same direction, or alternate them for a pinwheel or chevron effect. The blanket becomes a puzzle, and you get to decide how it comes together.

Materials You Will Need

One of the best things about this project is its flexibility. You can use almost any yarn weight and corresponding needle size, which makes it ideal for stash-busting. That said, here are some general guidelines.

Yarn: A worsted weight yarn (approximately 200 yards per 100g) is the most beginner-friendly choice because it works up quickly and the stitches are easy to see. You will need roughly 800–1,200 yards total for a baby blanket, and anywhere from 2,500–4,000 yards for a generous throw. The exact amount depends on how large you make your individual squares and how many you join together.

For a classic look, choose two or three complementary colors and alternate them across your squares. For a scrappy, eclectic blanket, use up every partial skein you own — this is a perfect stash project.

Needles: For worsted weight yarn, US size 7 (4.5mm) or US size 8 (5.0mm) needles work beautifully. Use whatever needle size gives you a fabric you like. Gauge is flexible here — you are not fitting a garment, so a slightly tighter or looser swatch is perfectly fine.

Other supplies you will need: a tapestry needle for weaving in ends and seaming squares together, scissors, stitch markers (optional but helpful), and a tape measure.

Understanding the Pattern Logic

Before you cast on, it helps to understand the underlying structure of the mitered square so you can adjust the size to suit your project.

Every mitered square starts with a cast-on that is always an odd number. This is because the central decrease happens at the exact center stitch, which means you need a stitch to sit precisely in the middle. The formula looks like this:

Cast on = (desired stitches per side × 2) − 1

So if you want a square with 21 stitches along each side before decreasing, you cast on 41 stitches: (21 × 2) − 1 = 41.

The number of rows you knit equals the number of stitches you cast on along one side. So for a 41-stitch cast-on, you will work 21 rows to complete the square, ending with 1 stitch remaining, which you either bind off or pick up to start the next square.

This tutorial uses a cast-on of 41 stitches (giving you approximately a 4-inch square in worsted weight on a US 7 needle), but you can easily scale up or down using this formula.

The Mitered Square Pattern

Abbreviations

Before we begin, here are the abbreviations used throughout this pattern.

CO: cast on
K: knit
P: purl
RS: right side
WS: wrong side
sl: slip
k2tog: knit two together
psso: pass slipped stitch over
BO: bind off

Stitch Pattern: Garter Stitch

This tutorial uses garter stitch (knit every row) for the body of the square. Garter stitch lies flat without curling, requires no blocking to look tidy, and shows off the diagonal decrease line beautifully. Once you are comfortable with the basic mitered square, you can experiment with seed stitch, moss stitch, or even stripes.

The Center Double Decrease

The key decrease in mitered square knitting is the center double decrease (also called a CDD). Here is how to work it.

Slip 2 stitches together knitwise (as if to k2tog), knit 1, pass the 2 slipped stitches over the knitted stitch. This removes 2 stitches at once and leaves a clean, centered vertical line.

You can also use a sl1-k2tog-psso decrease, which achieves the same result: slip 1 stitch knitwise, knit the next 2 stitches together, then pass the slipped stitch over. Both methods work well — choose whichever feels more natural in your hands.

Step-by-Step Instructions for One Mitered Square

Cast on 41 stitches using your preferred cast-on method. The long-tail cast-on works beautifully here because it gives a tidy, elastic edge.

Mark the center stitch. Place a stitch marker on either side of stitch 21 (the center stitch). This makes it easy to find your decrease point on every right-side row.

Row 1 (RS): Knit to 1 stitch before the first marker, work the center double decrease (removing the marked stitch and the stitch on either side), knit to end. (2 stitches decreased; 39 stitches remain.)

Row 2 (WS): Knit across.

Repeat Rows 1 and 2 until 3 stitches remain.

Final decrease row: Work the center double decrease over the remaining 3 stitches. 1 stitch remains.

Cut yarn, leaving a 6-inch tail, and pull the tail through the remaining stitch to secure it.

That is your first mitered square! Take a moment to appreciate it. The diagonal line running from one corner to the opposite corner is crisp and clean, and the edges form a perfect square.

Making a Striped Mitered Square

One of the most popular variations of the mitered square blanket uses two-row stripes. This is an excellent way to use up partial skeins and create a colorful, dynamic blanket without any complicated color work.

Simply change colors every 2 rows (i.e., every time you complete one RS row and one WS row). Because garter stitch stripes appear as single ridges, alternating two colors every 2 rows creates a clean, classic stripe pattern.

To switch colors, drop the old color at the end of a WS row and pick up the new color to begin the next RS row. You don’t need to cut the yarn every time — if you’re alternating between just two colors, you can carry the unused color up the side of the work loosely and pick it up when you need it again.

How Many Squares Do You Need?

The answer depends entirely on how large you want your blanket to be and how large each individual square is. Here is a general reference guide based on squares that finish at approximately 4 inches each (using worsted weight yarn and a 41-stitch cast-on).

For a baby blanket measuring roughly 28 × 32 inches, you will need approximately 56 squares arranged in a 7 × 8 grid.

For a lap blanket measuring roughly 36 × 48 inches, you will need approximately 108 squares in a 9 × 12 grid.

For a generous throw measuring roughly 48 × 60 inches, you will need approximately 180 squares in a 12 × 15 grid.

These are approximate guides. The finished size of each square can vary with yarn weight, needle size, and individual tension, so always swatch at least a few squares before calculating your final total.

Knitting the Squares Efficiently

Once you have knitted a handful of squares, you will find that you settle into a comfortable rhythm. Here are a few tips for working through a large batch of squares without losing your mind.

Knit in batches by color. Rather than knitting one square at a time and weaving in ends constantly, knit all of one color together, or at least knit five or ten squares in a row before stopping to weave in ends. This keeps you in a flow state and makes the process feel faster.

Leave long tails. When you cast on, leave a tail that is at least 12 inches long. This gives you enough length to later use for seaming, which reduces the number of extra ends you need to manage.

Use a yarn bowl or bag for each color. If you’re working with multiple colors, keeping each skein in its own small bag prevents tangling and makes it easy to grab the color you need without hunting through a pile of yarn.

Count your decreases. If you lose count of your rows, just count the ridges along one edge of the square. Each ridge equals 2 rows.

Joining the Squares

Once you have knitted all your squares, it is time to join them into a blanket. There are several methods for seaming knitted squares, and the best choice depends on the look you want.

The Mattress Stitch

Mattress stitch creates an invisible seam on the right side of the fabric and is the most popular method for joining knitted pieces. Lay two squares side by side with their right sides facing up. Thread a tapestry needle with a length of matching yarn (or a contrast color if you want the seam to be decorative). Insert the needle under the horizontal bar between the first and second stitches on one side, then under the corresponding bar on the other side. Pull the yarn through gently and continue along the seam, pulling the yarn snug every few stitches to close the join. This creates a seamless join that disappears into the fabric.

The Crochet Slip Stitch Join

If you know basic crochet, a slip stitch join works very well for mitered squares and gives a slightly raised, decorative seam on the right side of the blanket. Hold two squares with right sides together. Insert a crochet hook through both edge stitches, draw up a loop of yarn, and pull it through. Continue along the seam. When you turn the work to the right side, you’ll see a neat chain running along the join.

The Three-Needle Bind-Off

This method joins two live-stitch edges together and works best if you’ve planned ahead and left your final stitch live (rather than binding off) on each square. It creates a very clean, flat seam. Place both needles parallel with right sides facing each other, then use a third needle to knit through the first stitch of each needle simultaneously and bind off as you go.

For most blankets, arranging the squares on a flat surface first — a bed or a large piece of foam — and pinning them in place before seaming is enormously helpful. This lets you preview the final layout and make any color adjustments before you commit.

Adding a Border

A simple border transforms a blanket from a collection of squares into a finished object. For a mitered square blanket, a garter stitch border is a natural choice because it matches the texture of the squares themselves.

Pick up stitches along the entire outer edge of the joined blanket at a ratio of approximately 3 stitches for every 4 rows, or 1 stitch for every cast-on stitch along the cast-on and bound-off edges. Work in garter stitch (knit every row) for 6 to 10 rows, or however wide you’d like the border to be. Bind off loosely on the right side for a tidy finish.

At the corners, you’ll need to increase on right-side rows to turn the corner neatly. Work a yarn-over or a knit-front-and-back in the corner stitch to add 2 stitches at each corner on every other row. This keeps the corner flat and square rather than pulling inward.

Blocking Your Blanket

Blocking is the finishing step that transforms hand-knitted fabric from “nice” to “polished.” For a mitered square blanket, wet blocking works beautifully.

Soak the finished blanket in cool water for 20 to 30 minutes, gently pressing the water into the fabric without wringing or twisting. Lift the blanket carefully out of the water and press it between two towels to remove excess moisture. Then lay it flat on a blocking mat or a clean carpet and ease it gently into its final shape. Use rust-proof pins to hold the edges in position if needed. Let it dry completely, which can take 24 to 48 hours depending on the fiber content and room temperature.

Wool and wool-blend yarns respond most dramatically to blocking. Acrylic and acrylic-blend yarns can be steam blocked — hold a steam iron a few inches above the fabric and let the steam relax the fibers without pressing down directly.

Design Inspiration: Arranging Your Squares

Here is where the real fun begins. Because each mitered square has a strong diagonal line through its center, the way you orient individual squares dramatically changes the look of the finished blanket.

If you arrange all the squares so their diagonal lines run in the same direction, the overall blanket has a uniform, graphic quality — like a field of arrows or falling rain.

If you alternate the orientation of adjacent squares (rotating each one 90 degrees from its neighbor), the diagonal lines form a series of V-shapes or chevrons across the blanket.

If you arrange groups of four squares with their center points meeting in the middle, the lines create pinwheel or windmill shapes that repeat across the surface.

Sketch out your arrangement on paper before you begin seaming, or lay your squares out on the floor and take a photograph to help you plan. It is much easier to pivot at this stage than after everything is sewn together.

Troubleshooting Common Issues

My square isn’t square. This is almost always a tension issue. If your square is too tall and narrow, try going up a needle size. If it’s too wide and short, try going down a needle size. Gauge in garter stitch can vary significantly from knitter to knitter.

My center decrease line looks uneven. Make sure you’re working the double decrease consistently on every right-side row and not occasionally working it on wrong-side rows. Also check that your stitch marker is in the right place — it should mark the center stitch, not the gap between stitches.

My edges are curling. Garter stitch doesn’t curl, so if your edges are curling, you may have accidentally switched to stockinette on some rows. Double-check that you’re knitting every row, not alternating knit and purl rows.

My squares look different sizes. If you’re working from a stash of different yarn types, tension differences between yarn weights can make squares look inconsistent. This is perfectly normal and charming in a scrappy blanket. If you want more uniformity, work all squares in the same yarn weight.

A Note on Yarn Substitutions

This pattern is wonderfully yarn-agnostic. You can make a luxurious blanket from 100% merino wool, a practical everyday throw from a machine-washable acrylic blend, or a rustic, textured version from a linen-cotton blend. Just keep in mind that natural fibers like wool and cotton block beautifully, while pure acrylics will need steam blocking and may never fully even out their texture.

If you’re shopping for yarn specifically for this project, look for something with good stitch definition so the decrease lines pop. Heathered or speckled yarns create a subtle, interesting effect in mitered squares. Variegated yarns can be lovely but can also obscure the geometric lines of the miter — worth sampling a few squares before committing to a full blanket’s worth.

Final Thoughts

A mitered square blanket is one of those knitting projects that rewards you long after it’s finished. Every time you unfold it or watch someone snuggle under it, you’ll see all those little squares clicking together into something warm and substantial. The project teaches you to work methodically, to embrace repetition, and to trust that all those individual pieces will eventually add up to something beautiful.

Start with a small swatch square to check your gauge and get comfortable with the center double decrease