Lines of Symmetry
A line of symmetry divides a shape into two halves that are mirror images of each other. Regular polygons have as many lines of symmetry as they have sides.
If you can fold a shape along a line and both halves match exactly, that line is a line of symmetry (also called a mirror line).
Key facts to remember:
- An equilateral triangle has 3 lines of symmetry.
- A square has 4 lines of symmetry.
- A regular pentagon has 5 lines of symmetry.
- A rectangle (non-square) has 2 lines of symmetry.
- An isosceles triangle has 1 line of symmetry.
- A parallelogram (non-rectangle) has 0 lines of symmetry.
- A circle has infinitely many lines of symmetry.
In general, a regular polygon with sides has lines of symmetry.
Explore: lines of symmetry
Use Next and Prev to cycle through shapes, and Show lines to reveal their lines of symmetry.
Watch it work
Question: How many lines of symmetry does a regular hexagon have? Describe where they go.
Step 1: A regular hexagon has 6 sides, so it has lines of symmetry.
Step 2: Three lines pass through opposite vertices (corner to corner).
Step 3: Three lines pass through the midpoints of opposite sides (side to side).
Have a go
Q1. How many lines of symmetry does a scalene triangle have?
0 — no sides or angles are equal, so there is no line of symmetry.
Q2. How many lines of symmetry does a rhombus have?
2 — one along each diagonal.
Q3. A regular octagon has how many lines of symmetry?
8 — it has 8 sides, so 8 lines of symmetry.
Q4. Draw or describe the line of symmetry of the letter A.
A vertical line down the middle of the letter.
Q5. Does a kite have any lines of symmetry? If so, how many?
Yes, 1 line of symmetry, along the diagonal that joins the two vertices where different pairs of equal sides meet.