How to Knit a Mitered Square Blanket – Free Tutorial

There is something deeply satisfying about a mitered square blanket. Each little square is its own small victory — a perfect, self-contained shape that grows from a pile of cast-on stitches into a neat, diagonal-striped block of fabric. String dozens of them together and you have something truly beautiful: a blanket with movement and structure, a patchwork feel without the patchwork complexity, and an endlessly customizable canvas for your yarn stash.

This tutorial will walk you through everything you need to know to knit your own mitered square blanket from start to finish. Whether you are a confident beginner who has mastered the knit stitch and is ready for a new challenge, or an experienced knitter looking for a rhythmic, satisfying stash-buster project, this is the blanket for you. We will cover materials, gauge, how to knit a single mitered square, how to join squares as you go, and how to plan your color arrangement. By the end, you will have all the tools you need to make a blanket that looks like it came from a boutique shop — because it did. Your boutique. Your shop.

Let’s get into it.

What Is a Mitered Square?

Before we talk yarn and needles, it helps to understand what makes a mitered square different from a regular knitted square.

A mitered square is worked from the outside edges inward, with a central decrease running diagonally from two corners to the center of the square. This decrease is usually a double decrease (a slip-slip-knit decrease or a centered double decrease) that pulls the fabric toward the middle on every other row. The result is a square with a visible diagonal line running through it — which is part of the charm. When you hold it up to the light, the fabric has a subtle bias and a beautiful texture that looks intentional and polished.

Because each square is worked flat in rows, you can easily knit them back and forth on straight needles or circular needles held flat. No special equipment required. And because the construction is self-contained, you can pick up and put down the project between squares, making this a perfect companion for busy people who knit in small windows of time.

Materials You Will Need

Yarn: This pattern works beautifully with any worsted weight yarn, which is the most widely available and beginner-friendly weight. You can also use DK or bulky yarn — just adjust your needle size accordingly and expect a slightly different finished size. The beauty of a stash-buster blanket is that you do not need a specific amount of any single colorway. You just need a general total yardage. For a lap blanket (roughly 36 by 36 inches), plan on approximately 1,200 to 1,500 yards of worsted weight yarn. For a full throw (roughly 48 by 60 inches), aim for 2,500 to 3,500 yards.

Needles: US size 7 (4.5mm) or US size 8 (5.0mm) straight or circular needles work well for most worsted weight yarns. Adjust to get your preferred gauge and fabric density.

Additional supplies: Scissors, a yarn needle for weaving in ends, stitch markers (optional but helpful), and a measuring tape.

Optional: A blocking mat and rust-proof pins if you want to block your finished blanket for a more polished look.

A Note on Gauge

Gauge matters for this project in a practical but forgiving way. Because you are joining a series of squares together, the exact finished size of your blanket will depend on how large each individual square knits up, and that depends on your personal gauge. A tighter knitter will produce smaller squares; a looser knitter will produce larger ones.

To check your gauge before diving in, knit a single test square following the instructions below, then measure it. If you want larger squares, go up a needle size. If you want smaller squares, go down a needle size. The pattern is infinitely adjustable — no math required beyond deciding how many squares to make in each direction.

For this tutorial, our working gauge produces a square that is approximately 5 inches by 5 inches using worsted weight yarn on US size 8 needles.

How to Knit a Single Mitered Square

Each square in this blanket is knitted the same way. Once you have made one, you will find that the rhythm becomes almost meditative — knit across, turn, knit the decrease, knit across, turn again. Your hands will know what to do before your brain does.

Cast on 41 stitches using your preferred cast-on method. The long-tail cast on gives a neat, elastic edge and is highly recommended here.

If you want to knit in two colors (which creates those gorgeous diagonal stripes), cast on using Color A. The total stitch count will always be an odd number, which ensures that the center decrease falls exactly in the middle.

Row 1 (Right Side): Knit across all 41 stitches. This is your first row, worked from one edge to the other.

Row 2 (Wrong Side): Knit across all stitches. Yes, you are knitting on the wrong side too. This blanket is worked in garter stitch (knit every row), which gives it beautiful ridges and lies flat without curling. No seaming out edges, no blocking every single square to stop it from rolling — garter stitch is a gift.

Row 3 (Right Side — Decrease Row): Knit 19 stitches, then work a centered double decrease. To do this: slip 2 stitches together as if to knit them together (inserting your needle into both stitches at once from left to right), knit 1, then pass the 2 slipped stitches over the knitted stitch. You have just decreased by 2 stitches and the decrease leans nicely toward the center. Knit the remaining 19 stitches to the end of the row. You now have 39 stitches.

Row 4 (Wrong Side): Knit across all stitches.

Continue in this pattern — knit one plain row, work a decrease row — until you have 3 stitches remaining on your needle.

Final Decrease: Work a centered double decrease over those final 3 stitches. You will be left with 1 stitch. Break your yarn, pull the tail through the last stitch, and pull snug. Your square is complete.

If you are working in two colors, switch colors every two rows (after completing a wrong-side row, change to the next color at the beginning of the next right-side row). This creates clean, even stripes. Carry the yarn not in use loosely up the side of your work rather than cutting and rejoining each time — this saves you from an enormous number of ends to weave in later.

Joining Squares as You Go

One of the most efficient methods for making a mitered square blanket is the join-as-you-go technique, which eliminates the need to seam individual squares together at the end. Instead, you pick up stitches along the edge of a finished square and incorporate them into the cast-on of your next square, connecting the two as you knit.

Here is how it works once you have your first square complete.

For the second square in a row: With your finished square lying flat in front of you, use a needle and your yarn to pick up and knit stitches along the right edge of the finished square. You will pick up approximately 1 stitch for every 2 rows of garter stitch. Since your square has 20 decrease rows (decreasing from 41 stitches to 1), the edge has 40 ridges of garter stitch, giving you approximately 20 stitches to pick up along the vertical edge.

Then use a cable cast-on or backward loop cast-on to add the remaining stitches you need to reach your full 41-stitch cast-on count. The joining edge accounts for half of your stitches, and the cast-on provides the other half (plus your center stitch). This is why your cast-on must always be an odd number: the center stitch is the pivot point for the whole square.

Once you have 41 stitches on your needle (20 picked up, 1 center stitch from your pick-up row, 20 cast on), knit your square as normal. When you work the decrease row, the center decrease will fall right at the junction between the two squares, and as the square grows, it will naturally knit itself to its neighbor.

For additional squares within the blanket’s interior (squares that must join to both a horizontal neighbor and a vertical neighbor), you will pick up stitches from two finished squares simultaneously. This sounds complicated but is actually very logical once you have done it once. Pick up stitches from the right edge of one finished square, use your center stitch marker to mark the halfway point, then pick up stitches from the top edge of the square below. The two sets of pick-up stitches account for almost all of your stitch count, with just a center stitch needed to tie everything together.

Work through your first few squares slowly. Mark the center stitch with a stitch marker so you always know exactly where your decrease falls. After four or five squares, you will stop needing the marker because the rhythm will be deeply familiar.

Planning Your Color Layout

Here is where the real creative fun begins. A mitered square blanket is one of the best vehicles for using up leftover yarn, and the color arrangement you choose will define the whole character of the piece.

Scrappy and random: Simply grab whatever yarn is on top of your stash basket and knit. Do not overthink it. Alternate colors every two rows within each square, or make each square a single solid color. The variation and surprise of a scrappy blanket has an energy that a carefully planned palette cannot replicate.

Gradient: Arrange your yarn colors from light to dark, or choose three or four colors from the same color family (for example, pale blush, dusty rose, deep mauve, and burgundy) and cycle through them across the blanket. This creates a sophisticated, cohesive look that is especially beautiful in neutrals.

High contrast stripes: Choose two strongly contrasting colors — navy and cream, forest green and mustard, charcoal and white — and alternate them in two-row stripes within every square. The diagonal decrease line will pop dramatically against the striping, making the whole blanket look graphic and geometric.

Block color sections: Assign different sections of the blanket to different colorways. Make a cluster of warm-toned squares in one corner, cool-toned squares in another, and let them blend and meet in the middle. This works especially well for larger blankets where you have more real estate to play with.

Before you commit to a layout, lay your finished squares out on a flat surface and rearrange them until you find an arrangement that pleases you. Taking a photo with your phone helps — it collapses everything into a flat, two-dimensional view that makes color relationships easier to evaluate than viewing the actual textured knitting does.

Finishing the Blanket

Once all of your squares are joined, your blanket will be almost complete. You will have a perimeter of raw edges — the outer sides and top and bottom of the squares around the border — that need a finishing treatment.

The easiest finish is a simple garter stitch border. Pick up stitches evenly around the entire perimeter of the blanket, placing a marker at each corner. Knit every row, and on right-side rows, work a paired increase (such as a make-1 left and make-1 right on either side of each corner marker) to keep the border flat. Knit 10 to 20 rows, then bind off loosely. A loose bind-off is important: if the bind-off is too tight, the edge will pull inward and the blanket will not lie flat.

Alternatively, you can work a simple single crochet border if you are comfortable holding a crochet hook. This gives a clean, stable edge and is particularly effective if your blanket has a lot of color variation — a single solid crochet border in a neutral color ties everything together.

Weave in all your ends securely. If you have been carrying yarn up the sides of your squares rather than cutting between color changes, you will have significantly fewer ends to deal with. Any ends that remain should be woven in along the seam lines between squares, where they will be hidden naturally by the construction.

Blocking Your Finished Blanket

Blocking is the step that transforms a handknit project from something that looks handmade into something that looks handcrafted — and there is a meaningful difference between those two things.

To wet block your blanket, submerge it in cool water with a small amount of wool wash or gentle dish soap. Allow it to soak for 20 to 30 minutes until the fibers are fully saturated. Do not wring or twist the blanket. Gently press the water out, then roll the blanket in a clean towel and press again to remove as much moisture as possible.

Lay the blanket flat on a blocking mat or clean floor covered with towels. Smooth it into shape with your hands, making sure the squares are aligned and the edges are straight. Pin the corners and edges if needed. Allow the blanket to dry completely — which may take 24 to 48 hours depending on the yarn weight and humidity in your home.

The difference after blocking is remarkable. Stitches even out, the fabric relaxes, and the blanket grows slightly in size. Garter stitch in particular benefits enormously from blocking.

Tips for Success

Knit your squares in batches. Making ten or fifteen squares before you join them keeps the project feeling fresh, and you can spend an evening doing nothing but the satisfying work of joining everything together.

Keep a loose tension throughout. Mitered squares can become slightly stiff if knitted very tightly, especially around the decrease line. A slightly looser hand produces a more drapey, comfortable finished fabric.

Label your yarn. If you are working from your stash, tape a small piece of yarn to an index card and note the weight and yardage so you can track how much you are using. Stash-busting without records can lead to surprise shortages when you are three squares from finished.

Embrace imperfection. Handknitting is not machine knitting, and slight variations in tension between squares are part of the charm. Blocking will even out many inconsistencies, and the mitered structure naturally hides a multitude of small variations.

Final Thoughts

A mitered square blanket is one of those projects that rewards patience without demanding it. You can knit a square in an evening. You can join a row of squares on a Sunday afternoon. The blanket grows incrementally, visibly, satisfyingly — and at every stage it is already beautiful, already worth the effort you have put in.

It is also, quietly, an excellent teacher. By the time you finish, you will have worked a double decrease hundreds of times without even thinking about it. You will have picked up stitches, joined seams, managed multiple colors, and made something entirely your own from yarn that might otherwise have stayed in a drawer forever.

Cast on those first 41 stitches. Knit across. Turn. Knit the decrease. Watch the square take shape beneath your hands.

That is how it begins. The rest takes care of itself.

Happy knitting from A Bee In The Bonnet — where every stitch is worth making.