How to Knit 2-Color Mitered Square Half Triangles

Here’s how to knit 2-color mitered square half triangles with a CDD spine seam. With two different yarn colors of your choice, this shape is formed by decreasing stitches to that meet in the middle. Start knitting your duotone squares with these detailed photo instructions, cast on cheat sheet, and free printable written pattern.

Mitered square half triangle knitted with white and orange colored yarn.

A Closer Look

  • Colorwork Designs: Use any two yarn colors to create unique designs.
  • Easy to Memorize: After knitting a few squares, you’ll be able to easily remember the pattern without needing to refer to the instructions.
  • Lays Flat: Because this square is comprised of all knit stitches, it easily lays flat.
  • Are CDD Mitered Squares Reversible? At first look, this seems to be a reversible pattern. However, with this CDD technique and knitting with two yarn colors, the right side of the work displays the ridged seam while the wrong side has a flatter texture.
Four half-triangle knitted mitered squares arranged in a pinwheel design.

2-Color Mitered Square Construction

These Mitered squares are created by decreasing stitches as you knit, forming a two-toned square with lines that converge in the center. The decreases draw the edges inward, creating the distinct mitered look.

Unlike a basic Garter Stitch square, which can stretch lengthwise and lose its shape over time, mitered squares maintain their shape thanks to their opposing stitch directions. This structural integrity makes them perfect for projects like blankets and scarves that receive a lot of use.

For this type of construction, you begin with two yarn colors and an odd number of stitches, working from the outer edges toward the center. The center double decrease (CDD) technique is used to form the square’s symmetrical, neat appearance.

2-color mitered squares with white, yellow, and green yarn colors.

Watch Video Tutorial

Knitting Tutorial for Half Triangle Mitered Squares Coming Soon!

How to Knit 2-Colored Half-Triangle Mitered Squares

Casting On

Your cast on edge will be length of two sides of your square. Therefore, decide how many total stitches to cast on based on your yarn gauge and square size desired.

Begin by casting on an odd number of stitches. The number of stitches determines the total length of two edges of your square.

IMPORTANT: Cast On Color B first, then Color A.
In this photo example below, Color A is blue and Color B is white. Therefore, I am casting on Color B (white) first, then Color A (blue) onto my needle in preparation to knit.

Hands casting on two different yarn colors onto a knitting needle.

Calculate Number of Stitches of Each Color to Cast On

  • Color B Cast On Stitches = (Total Stitches – 1) / 2
  • Color A Cast On Stitches = Color B Cast On + 1

Example: Casting on a total of 13 stitches

  • Color B Cast On Stitches = (13 – 1) / 2 = 6 Stitches
  • Color A Cast On Stitches = 6 + 1 = 7 Stitches

Your yarn and needle size will determine the number of stitches required for your desired square size. I have created this helpful guide to determine the number of stitches to cast on for each color.

Yarn DK #3 • Needle 6 US (4.0 mm)

Square Size (inches)345678
Cast On Total Stitches273745556373
Color A Cast On141923283237
Color B Cast On131822273136
Yarn per Square (yards)192531374349

Yarn Worsted #4 • Needle 8 US (4.5 mm)

Square Size (inches)345678
Cast On Total Stitches253341495765
Color A Cast On131721252933
Color B Cast On121620242832
Yarn per Square (yards)192532384451

Yarn Bulky #5 • Needle 10 US (6.0 mm)

Square Size (inches)345678
Cast On Total Stitches192531374349
Color A Cast On101316192225
Color B Cast On91215182124
Yarn per Square (yards)101417212428

Yarn Super Bulky #6 • Needle 13 US (9.0 mm)

Square Size (inches)345678
Cast On Total Stitches131721252933
Color A Cast On7911131517
Color B Cast On6810121416
Yarn per Square (yards)7912141719

About the Slip Stitch Edge

To help sew our squares together, we are going to create uniform edges on all 4 sides of our square. To do so, we will slip the first stitch of every row. This will become incredibly helpful when it is time to seam our squares together.

Sl1P WYIF: Slip One Stitch Purlwise with Yarn in Front.

Right Side of Work (odd numbered rows)

Again, it is important to first Cast On Color B onto your needle, then Color A.

After casting on, begin knitting with Color A. After slipping your first stitch with the yarn in front, bring the yarn between the first and second stitches to the back of your work. Then knit until you have 2 stitches of Color A remaining on your needle.

Hands knitting a center double decrease with needles and yarn.

Once you have those last 2 stitches of Color A on your needle, then knit your Center Double Decrease (CDD):

  • With Color A Sl1P WYIB (Slip one stitch purlwise with the yarn in back);
  • Colors A & B K2TOG (Knit the next two stitches together);
  • Color A PSSO: Pass the first stitch over (2 Sts Decreased).
  • Twist Yarns: Place Color B Over Color A, then Bring Color A to Front;

Once you have decreased three center stitches into one, continue knitting with Color B all the way down the row.

Hands decreasing knitting stitches with a k2tog and psso technique.
Twisting yarn demonstration to knit two colors together.

Wrong Side of Work (even numbered rows)

  • On the wrong side of your work, with Color B Sl1P WYIF, bring the yarn to the back, and knit to the end of Color B. and knit all stitches to the end of the row.
  • Twisting Yarns: Before switching to Color A, Place Color A Over Color B, then Bring Color B to Front;
  • Knit the end of the row with Color A.

Continue knitting rows 1 & 2

Your knitted rows become increasingly smaller (and faster to knit) as each right-sided row is decreased by two stitches. Continue the above pattern until you have five stitches remaining on your needle.

  • With Color A: Sl1P WYIF, Bring Yarn to Back, Sl1P WYIB;
  • Colors A & B: K2TOG
  • Color B: PSSO (2 Sts Decreased);
  • Color B: K1.
Finishing knitting a mitered square.

Finishing

  • With the 3 stitches remaining on your needle, cut both yarn colors;
  • Thread tapestry needle with Color A;
  • Thread yarn tail through the front of the 3 open stitches and cinch;
  • Slip knitting needle out of 3 rem sts;
  • Finally, weave in all yarn tails.

Action Items

  • Design Your Own: Feel free to get creative with your squares—experiment with different colors and patterns to craft something that’s uniquely yours!
  • Blocking: Before sewing your squares together, wet-blocking is highly recommended to create uniformed sized squares.
  • Join your squares – Sew squares together with the mattress stitch.
A half-triangle knitted mitered squares in white and yellow yarn colors.

Assembling Design Patterns

I’ve had so much fun experimenting with different color combinations and coming up with new blanket designs using a mix of solid and two-color mitered squares.

As an Amazon Associate, I earn from qualifying purchases.

One of my favorite tools for planning designs is the Half-Square Triangle Quilt Block Design Deck. Though originally made for quilters, this set of cards features a variety of half-square triangles and solid squares, making it easy and fun to explore countless color block possibilities.

Hands working with the Half-Square Triangle Quilt Block Design Deck.

Mitered Square Knitting Collection

In addition to this two-color half triangle square, get printable written instructions for these differently constructed mitered patterns, as well.

Printable Knitting Instructions

Mitered Half Square Triangle Knitted in white and dark orange yarn colors.

Printable Knitting Pattern

Knitting pattern instructions of a 2-Colored Mitered Half Square Triangle with a CDD Spine Seam.

Makes: Knitted 2-Color Mitered Half Square Triangle
Prep Time: 5 minutes
Active Time: 30 minutes
Additional Time: 5 minutes
Total Time: 5 minutes
Difficulty: Intermediate

Materials

  • Yarn - Any Gauge

Tools

  • Knitting Needles - Appropriate Size for Yarn
  • Tapestry Needle
  • Scissors

Instructions

Cast On an Odd Number of Stitches

Your cast on edge will be length of two sides of your square. Therefore, decide how many total stitches to cast on based on your yarn gauge and square size desired. See Cast On Cheat Sheet in the post above.

Calculate Number of Stitches of Each Color to Cast On:

  • Color B Cast On Stitches = (Total Stitches - 1) / 2
  • Color A Cast On Stitches = Color B Cast On + 1

Example: Casting on a total of 11 stitches

  • Color B Cast On Stitches = (11 - 1) / 2 = 5 Stitches
  • Color A Cast On Stitches = 5 + 1 = 6 Stitches

Cast On Color B, then Color A.

Knitting Pattern

Row 1 (Right Side):

  • Color A: Sl1P WYIF, K to Last 2 Color A Sts, Sl1P WYIB;
  • Colors A & B: K2TOG, PSSO (2 Sts Decreased);
  • Twist Yarns: Place Color B Over Color A, then Bring Color A to Front;
  • Color B: K to end.

Row 2 (Wrong Side):

  • Color B: Sl1P WYIF, Bring Yarn to Back, K end of Color B;
  • Twist Yarns: Place Color A Over Color B, then Bring Color B to Front;
  • Color A: K to end.

Continue knitting rows 1 & 2 until 5 Sts Rem on the right side

5 Sts (Right Side):

  • Color A: Sl1P WYIF, Bring Yarn to Back, Sl1P WYIB;
  • Colors A & B: K2TOG, PSSO (2 Sts Decreased);
  • Color B: K1.

Finishing:

  • 3 Sts Rem
  • Cut both yarn colors
  • Thread tapestry needle with Color A
  • Slip knitting needle out of 3 rem sts,
  • Thread yarn tail through the front of the 3 open sts and cinch,
  • Weave in all yarn tails.

Notes

KNITTING TECHNIQUES & ABBREVIATIONS

Love collecting free knitting patterns?

Follow Studio Knit on Pinterest by clicking the logo.

Kristen McDonnell
Author & Designer

After publishing her first knitting tutorial video, Kristen founded StudioKnit LLC. Enamored with teaching online, she films knitting lessons and designs from her vibrant production studio on Half Moon Bay’s California coast.

Kristen McDonnell is the author of the highly acclaimed book Knit Stitch: 50 Knit + Purl Patterns featuring vintage and unique designs.

Subscribe

Studio Knitโ€™s exclusive patterns straight to your inbox.