Naming Angles Worksheet – Angles, Types and Letter Names

Angle facts behind every answer key

Show the table

The key of a sheet is worked out from these facts, never typed in, and every figure is drawn to its true size: lay a protractor on a printed angle and it agrees with the key to the degree.

Name	Rule
Acute angle	less than 90°
Right angle	exactly 90°, marked with a small square
Obtuse angle	more than 90° and less than 180°
Straight angle	exactly 180°
Reflex angle	more than 180° and less than 360°
Complementary angles	two angles that add up to 90°
Supplementary angles	two angles that add up to 180°
Angles on a straight line	add up to 180°
Angles around a point	add up to 360°
Vertical (vertically opposite) angles	are equal
Angles in a triangle	add up to 180°
Angles in a quadrilateral	add up to 360°
Corresponding and alternate angles on parallel lines	are equal
Same-side interior (co-interior) angles on parallel lines	add up to 180°

Every sheet has a short code, printed at the foot of the sheet and of its answer key. A share link brings the same sheet back, figure for figure, so a key printed later still fits the copies you handed out.

How it works

This naming angles worksheet opens with 12 angles on one page. Students circle acute, right, obtuse, straight or reflex under the first 6, then name the last 6 with three letters. Press Print or PDF for the sheet and its key, or New sheet for 12 others.

Read the full guide

Types first, then letters

Acute, right, obtuse draws an angle with no size on it and prints the choices underneath. A right angle carries a small square; every other angle carries an arc. Name with three letters puts a lettered point on each ray and one at the vertex, and students write the three letters after a printed ∠. Under On the sheet, pick either task for a page of that one alone.

Reflex angles and sheet length

Reflex angles too is ticked at first, so angles past 180°, such as 320°, appear and reflex is a fifth choice. Untick it and four choices remain: acute, right, obtuse and straight. Problems sets 12, 16 or 24. The opening 12 fit one page; 16 or 24 take 2.

No protractor is needed. Acute angles stop at 80° and obtuse ones run from 100° to 165°, so none sits close to 90°.
Point letters never include I or O, which look like 1 and 0.
With only Name with three letters on the sheet, Reflex angles too is hidden, because that task draws angles from 25° to 160° only.

Questions and answers

How do you name an angle with three letters?

Write a point on one ray, then the vertex, then a point on the other ray. The vertex always goes in the middle, so ∠DCE and ∠ECD are the same angle. Where there is no risk of confusion, the vertex letter alone, ∠C, will do.

What are the types of angles?

An acute angle is less than 90°. A right angle is exactly 90°. An obtuse angle is between 90° and 180°, a straight angle is 180°, and a reflex angle is between 180° and 360°.

Does the worksheet have an answer key?

Yes. It prints after the sheet on a separate page. For types it gives the name and the size behind it, as in reflex (320°). For names it gives both orders and the vertex, as in ∠RQP or ∠PQR (vertex Q).

Which grade is it for?

Common Core standard 4.G.1 has grade 4 students draw right, acute and obtuse angles and identify them in two-dimensional figures. For that grade, untick Reflex angles too; straight angles stay on the sheet. The standard does not mention three-letter names.

Naming Angles Worksheets