# Types of Triangles

## Types of Triangles

There are different types of triangles.

Triangles can be classified by:

## Type of Triangle by Lengths of Sides

Triangles are a different type depending on how many sides are the same length (which is also how many angles are equal).

Triangles are equilateral, isosceles or scalene depending on whether 3, 2 or 0 side lengths and angles are equal.

### Equilateral Triangles

Equilateral triangles have 3 equal side lengths and angles. 3 sides are equal lengths. 3 angles are equal (60°).

### Isosceles Triangles

Isosceles triangles have 2 equal side lengths and angles. 2 sides are equal lengths. 2 angles are equal.

### Scalene Triangles

Scalene triangles have 0 equal side lengths and angles. 0 sides are equal lengths. 0 angles are equal.

## Type of Triangle by Angles

Triangles are a different type depending on the size of the angles inside the triangle.

Triangles are acute, obtuse or right triangles depending on whether all angles are acute (less than 90°), one angle is obtuse (more than 90°) or one angle is a right angle (90°).

### Acute Triangles

Acute triangles have all acute angles (less than 90°). 3 angles are less than 90°.

### Obtuse Triangles

Obtuse triangles have one angle that is obtuse (more than 90°, less than 180°). 1 angle is more than 90°. 2 angles are less than 90°.

Right triangles have one right angle (90°). 1 angle is 90°. 2 angles are less than 90°.

## Slider

Triangles can be classified by both lengths of sides and by angles. This means a triangle can be both acute and isosceles, or obtuse and scalene.

The slider below shows more real examples of the types of triangles.

Open the slider in a new tab

What is a triangle? What is an angle? What is an acute angle? What is an obtuse angle? What is a right angle? What are the interior angles of a triangle? Learn more about the types of triangles ( interactive widget)