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Impossible Triangle Foundation Paper Piecing Pattern

Free to print · Beginner · 12 pieces · 3 sections · 12″ block

Open and print this pattern
Pattern diagram in the suggested fabrics. Every line is a seam.

The Penrose impossible triangle built from cubes in true isometric view: three square bars meet at 120 degrees, and the end of one bar is drawn over the start of the next, so every corner looks right and the whole cannot exist. Three blues do the shading: light tops, medium sides, dark fronts.

Opens in the free FPP tool. Pick your fabrics and block size, then print or download the PDF. No account needed.

Finished size
12″ × 12″
Prints at
4 to 18″
Pieces
12
Sections
3
Smallest piece
about 1.2 sq in at 12″
Fabrics
4
Skill level
Beginner
Price
Free, no sign-up
Using it
Use it for anything you sew, including quilts you sell. Please don't resell or repost the pattern itself; share a link to this page instead.

About this pattern

The Impossible Triangle is a free foundation paper piecing (FPP) pattern from NiftyFifty: a 12-inch square block of 12 pieces sewn in 3 sections, using 4 fabrics, at a beginner skill level. It opens in NiftyFifty's free browser-based FPP tool, which prints mirrored foundations with 1/4-inch seam allowance at 4 to 18 inches. Every seam is a straight line, so the whole block is sewn with the flip-and-sew method.

Piece map

Letters are sections, numbers are sewing order. Dashed lines outline each section's foundation.

C1A4A3A1A2B1B2B3B4B5B7B6

How to sew it

  1. Open and printOpen the pattern in the free FPP tool, pick your fabrics and a block size (4 to 18 inches), and print or download the PDF. Print at 100% and check the 1-inch test square.
  2. Cut the foundations apartCut each section's foundation apart just outside its dashed line. The dashed line is the 1/4-inch seam allowance.
  3. Sew each section in number orderSew all 3 sections on the foundation, piece 1 first, then 2, 3 and on. Flip, press and trim the seam to 1/4 inch after each one. When a section is done, trim it on its dashed line.
  4. Join the sections
    • Join section A to section B along their shared straight seam.
    • Sew section C to the A+B assembly along their shared straight seam.
  5. Finish the blockPress, check that the block measures 12.5 inches square with seam allowance (12 inches finished), then tear the paper away.

Fabrics

  • Snow White71% of the block, 5 pieces
  • Navy11% of the block, 3 pieces
  • Cornflower10% of the block, 2 pieces
  • Sky Blue9% of the block, 2 pieces

Suggested colors. The printed pattern lists rough-cut sizes for whatever fabrics you choose.

Choosing a block size

Smaller blocks mean smaller pieces. Under about half a square inch, pieces get fiddly, so this one is most comfortable at 8″ and up.

Finished blockSmallest piece
6″ × 6″about 0.3 sq in
8″ × 8″about 0.5 sq in
10″ × 10″about 0.8 sq in
12″ × 12″ (as drafted)about 1.2 sq in
16″ × 16″about 2.1 sq in

A sewing tip for this block

The illusion depends on value, not hue. Lay your three fabrics out before you cut and make sure light, medium and dark are clearly different, even in a black-and-white phone photo.

What to make with it

The impossible triangle is a fun conversation piece for a math lover, a modern wall hanging or a striking pillow.

Try it in other colors

Try three greens, or three grays for a sleek modern look. Every fabric can be swapped in the FPP tool before you print.

Make it yours: every pattern is a starting point

These patterns are free and open to change. Think of each one as a starting point, not a finished rule: remix it into your colors, your size, your idea.

  1. 1Open itEvery pattern opens in the free FPP tool, no account needed.
  2. 2Change anythingSwap fabrics, change the size, move or add seams. The sewing order and sections update on their own.
  3. 3Save it as yoursSave your version to a free account and share it. Other quilters can then remix yours, credited to you.
Open and remix this pattern

Questions

What can I make with the Impossible Triangle block?

The impossible triangle is a fun conversation piece for a math lover, a modern wall hanging or a striking pillow.

Is this impossible triangle FPP pattern free?

Yes. The Impossible Triangle pattern is free to open, recolor and print, and you don't need an account. It opens in NiftyFifty's free FPP tool, which prints the foundations or downloads them as a PDF.

Is the Impossible Triangle block good for beginners?

Yes. It has 12 pieces in 3 sections, which makes it one of the gentler blocks to start paper piecing with.

How many pieces and sections does the Impossible Triangle block have?

12 pieces in 3 sections, using 4 fabrics. Each section is sewn on its own foundation, then the sections are joined along straight seams. The printed pattern numbers every piece in sewing order.

What size does it print?

It's drafted as a 12-inch finished block, and you can print it at 4 to 18 inches. At 12 inches the smallest piece is about 1.2 square inches; at 6 inches it's about 0.3 square inches.

Can I sell quilts I make from the Impossible Triangle pattern?

Yes. Use it for anything you sew, including quilts you sell. Please don't resell or repost the pattern itself; share a link to this page instead.

Is there a PDF of the impossible triangle pattern?

Yes. The FPP tool downloads a PDF with a 1-inch test square, a color key, an assembly map, the sewing order and every foundation drawn at exact size with 1/4-inch seam allowance. Print it at 100%.

Can I change the colors?

Yes. Open it in the FPP tool, click a piece, then click a fabric: over 600 real Kona and Bella solids plus thousands of prints. You can also move seams or add new ones before you print.

More like this

Part of: Free 3D and Optical Illusion FPP Patterns, Easy Foundation Paper Piecing Patterns for Beginners. Or browse all free FPP patterns.

Want to draw your own? The free FPP pattern maker turns any drawing into a printable pattern, and the Pattern Designer builds pieced blocks on a grid.