When inserting an isosceles triangle as a default shape in PowerPoint, it is not an equilateral triangle!

Hi, Comatine

The isosceles triangle in PowerPoint is not always a geometry-accurate equilateral triangle when inserted with a normal single selection or drag. So for drawings where exact side length and height matter, it is better to create the triangle in a constrained way instead of relying on the default inserted size.

Besides the solutions provided by the Q&A Assist, here are some suggestions you can try:

It is recommended that you select Insert > Shapes > Isosceles Triangle, then hold Shift while drawing the shape. This usually forces PowerPoint to keep the triangle’s proportions more regular instead of freely stretching it.

Another option is to select the triangle from the Shapes menu, then hold Ctrl and select on the slide instead of dragging. This inserts the shape at PowerPoint’s default regular proportion, which may be closer than manually drawing it.

If the triangle needs to be reused often, create one accurate triangle once, then copy it into a blank slide or template and reuse that version instead of inserting a new default triangle each time.

Thank you for your patience in reading, I hope this information has been helpful to you. 

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PowerPoint’s built‑in Isosceles Triangle shape is not defined as a mathematically perfect equilateral triangle. It is an adjustable isosceles triangle whose proportions are determined by the shape’s internal geometry and adjustment handle, not by enforcing the exact √3/2 height‑to‑width ratio.

Because of this, when the default isosceles triangle is drawn with a width of 30 cm, its height will not match the theoretical 25.9807 cm of a true equilateral triangle. This is expected behavior for the current shape implementation.

To obtain a precise equilateral triangle today, use one of these approaches instead of the default click‑to‑insert isosceles triangle:

1. Draw and convert from ink (Microsoft 365 / Office 2019):
   • On the Draw tab, turn on Ink to Shape.
   • Draw an equilateral triangle by hand.
   • PowerPoint converts the ink into an Equilateral triangle Office shape, which is distinct from the generic isosceles triangle and is intended to match the drawn equilateral proportions.
2. Use a macro or programmatic creation (as already done):
   • Create the triangle via VBA or Office Scripts, explicitly setting the coordinates so that side length and height follow the equilateral formula.
3. Manually adjust an isosceles triangle:
   • Insert an Isosceles Triangle.
   • Set its width to the desired side length.
   • Use the adjustment handle or the Size & Position dialog to tweak the height numerically until it matches the required equilateral height.

For future changes to make the default isosceles triangle equilateral, submit feedback through the PowerPoint feedback channels so the product team can consider it in later updates.

References:

• Convert ink to shapes in Office
• Draw and write with ink in Office