Some designs simply refuse to start from a square. A flower with three petals, a calyx with three sepals, and a good portion of modular work all want an equilateral triangle, and trying to eyeball one usually ends with three very different angles.

This method removes the guesswork with a single reference: the horizontal half-line. One fold, one slanted valley-fold that lands the corner's diamond point on that line, and the same move mirrored on the other side — the triangle's edges are marked before you even reach for scissors. Seven short steps, every crease photographed, and one clean cut. Let's fold the triangle.

This page is for those who want the instruction to make an equilateral triangle out of square paper.

If you want to make a flower with three petals or a calyx with three sepals, you need paper in an equilateral triangle shape instead of a square. This page shows how to make an origami equilateral triangle from a square sheet.

In this instruction, I used 15cm x 15cm origami paper. Of course, the folding method is independent of paper size.

This is the front side of an origami paper.

This is the back side of an origami paper.

STEP 1.

Let us start with the front side facing up. Prepare to mountain-fold in half horizontally and then unfold.

STEP 2.

Mountain-fold in half horizontally and then unfold. Prepare to apply a slanted valley-fold. Make sure the upper-left corner (diamond) merges onto the horizontal half line after applying the valley-fold.

STEP 3.

Apply the slanted valley-fold of step 2. The diamond point should merge onto the horizontal half line. Prepare to unfold the valley-fold you have just applied.

STEP 4.

Unfold the valley-fold of step 3. Prepare to apply another slanted valley-fold. Make sure the upper-right corner (diamond) merges onto the horizontal half line after applying the valley-fold.

STEP 5.

Apply the slanted valley-fold of step 4. The diamond point should merge onto the horizontal half line after applying the valley-fold. Prepare to unfold the valley-fold you have just applied.

STEP 6.

Unfold the valley-fold of step 5. Prepare to cut the paper along the dotted lines with a knife or scissors.

STEP 7.

Cut the paper off along the dotted line of step 6. You can get the best result if you use a utility knife with a ruler. Congratulations! You have completed making an equilateral triangle.