Online Protractor: Measure Angles in Degrees

Measure angles on screen with an online protractor. Place the vertex, align both arms, and read the angle in degrees.

Protractor Active

Angle

Angle in degrees

Quick Usage

01. PLACE VERTEX

Place the vertex

Drag the center handle to the corner where the two sides of the angle meet.

02. ALIGN ARMS

Align both arms

Move the two endpoint handles until each arm follows one side of the angle. Longer arm spans can make visual alignment easier.

03. READ DEGREES

Read the angle

The tool reports the interior angle in degrees and updates the value as you adjust the arms.

Why Calibration Is Not Needed

The protractor calculates the angle from the positions of its arms in the tool's coordinate system. It does not need the physical-size calibration used to convert screen distances into cm, mm, or inches.

Acute, Right, and Obtuse

An acute angle is less than 90°, a right angle is 90°, and an obtuse angle is greater than 90° but less than 180°.

Place the Vertex Carefully

The center handle should sit exactly where the two sides of the angle meet. A small vertex error can change the reading, especially when the arms are short.

Align the Arms Clearly

Follow the visible edges you are measuring rather than estimating from nearby empty space. When the two sides are close together, zooming in on the page can make positioning easier.

Frequently Asked Questions

Common questions about degrees, vertices, angle calculation, and on-screen protractors.

How is the angle calculated on screen?▼

The tool calculates the angle between the two measurement arms from their positions in the browser's coordinate system.

Do I need to calibrate the screen to measure an angle?▼

No. Physical-size calibration is not required for the angle calculation because the result is expressed in degrees.

How do I measure an acute, right, or obtuse angle?▼

Place the vertex on the corner, align one arm with the first side and the other arm with the second side, then read the displayed degree value. Acute angles are below 90°, right angles are 90°, and obtuse angles are between 90° and 180°.

How can I make the angle easier to align?▼

Place the vertex carefully and move the endpoint handles farther along the two visible sides. A longer arm span can make small alignment differences easier to see.

Can this protractor measure an angle larger than 180°?▼

The current protractor measures the interior angle from 0° to 180°. It does not provide a separate reflex-angle measurement.

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