📐 Protractor Tool

Interactive protractor to measure and set angles on screen. Supports drag, snap, and 360° mode.

0°

angle

Snap 360° Mode

📷 Set Background Image

📋 Common angles reference

angle	Name	Radians	Examples & Uses
0°	Zero Angle	0	Reference Line
30°	-	π/6	Half of an equilateral triangle, one hour on a clock
45°	-	π/4	Half of a right angle, optimal projectile launch angle
60°	-	π/3	Interior angle of an equilateral triangle
90°	Right Angle	π/2	Perpendicular, interior angle of squares and rectangles
120°	-	2π/3	Interior angle of a regular hexagon
135°	-	3π/4	Interior angle of a regular octagon
180°	Straight angle	π	Lines and triangle interior angles
270°	-	3π/2	3/4 rotation
360°	Full angle	2π	1 full rotation, complete angle of a circle

🔷 Interior angles of regular polygons

Shape	Sides	Interior Angle	Sum of Interior Angles
Equilateral triangle	3	60°	180°
Square	4	90°	360°
Regular pentagon	5	108°	540°
Regular hexagon	6	120°	720°
Regular octagon	8	135°	1080°
Regular decagon	10	144°	1440°
Regular dodecagon	12	150°	1800°

Interior angle formula: (n-2) × 180° / n (n = number of sides)

📐 Types of angles

Acute angle (0° < θ < 90°): An angle smaller than a right angle. Every triangle always contains at least one acute angle.

Right angle (θ = 90°): The angle formed by two perpendicular lines. Fundamental in architecture and engineering.

Obtuse angle (90° < θ < 180°): An angle greater than a right angle but smaller than a straight angle.

Straight angle (θ = 180°): The angle that forms a straight line. The sum of supplementary angles is 180°.

Reflex angle (180° < θ < 360°): An angle greater than a straight angle but smaller than a full angle. Also called a reflex angle.

Full angle (θ = 360°): The angle of one complete rotation.

Usage and Application Examples

Drag the blue handle to freely adjust the angle
The red handle sets the baseline angle
Enable snap to automatically lock to specified increments (1°/5°/15°)
Preset buttons to set common angles with one click
Upload a photo and overlay the protractor to measure real-world angles
360° mode supports measuring angles around a full circle
Useful for checking angles in math homework and technical drawings
Also useful for verifying angles in DIY and furniture assembly
For checking roof pitch angles in architectural design
As a reference for perspective angles in art and design
To visually understand the relationship between angles and sides when learning trigonometry
For verifying bend angles in plumbing and electrical work

What is Protractor?

The Protractor Tool is a digital angle measurement instrument that lets you measure angles directly on your screen. Instead of using a physical protractor, you can drag and position an SVG overlay to measure any angle you need. This tool is perfect for designers, architects, educators, and anyone working with visual content who needs accurate angle measurements without leaving their browser.

How to Use

Open the tool and you'll see a circular protractor overlay on your screen. Drag the center point to position it where you need to measure. The two arms of the protractor can be rotated independently to align with the angle you're measuring. Most versions include a snap feature that helps align to common angles like 15°, 30°, 45°, and 90°. The current angle reading displays prominently on screen. Switch to 360° mode if you need to track full rotations, which is useful for circular designs and rotational measurements.

Use Cases

Graphic designers use this tool to verify angles in logos and design elements. Architects and engineers measure angles in floor plans and technical drawings. Students learning geometry can measure angles in diagrams without physical tools. Web designers align UI elements by checking the precise angles of rotated components. Photographers use it to measure angles in composition guides and rule-of-thirds overlays. The tool is invaluable for anyone needing to document or verify angular measurements in digital images.

Tips & Insights

The snap feature is a major time-saver when aligning to standard angles. For precise measurements, zoom in on your content before measuring. The 360° mode is helpful for tracking rotational values in animations and design systems. Keep in mind that on curved surfaces, the protractor shows the angle relative to the screen plane, not the actual 3D angle. For architectural work, always cross-check digital measurements with actual dimensions when precision is critical.

Frequently Asked Questions

How do I use this protractor tool?

Drag the two handles (blue circles) to set the angle. The angle displays large in the center. Use preset buttons to quickly set common angles.

What is the snap feature?

When snap is enabled, handles automatically align to 5° or 15° increments. Useful when you need precise angles.

What is 360° mode?

By default, it's a semicircle protractor measuring 0°–180°. With 360° mode enabled, you can measure full circle angles from 0°–360°.

Can I measure angles in photos?

Yes, click the "Set background image" button to load a photo and overlay the protractor to measure angles.

What is the measurement accuracy of this tool?

The protractor provides precision to 0.1 degrees, suitable for most practical applications. For professional engineering or scientific work requiring greater precision, external instruments are recommended.

What do the preset angle buttons do?

Preset buttons include common angles like 30°, 45°, 60°, 90°, and 180° for quick reference. Click any preset to instantly align the protractor to that exact angle, making it fast to verify specific angle requirements.

Can I save or export my angle measurements?

Angle measurements cannot currently be exported as files, but you can take a screenshot to save your work. You can also manually record the displayed angle value for reference.

Does snap precision work in 360° mode?

Yes, the snap feature remains active in 360° mode and snaps to nearby angle increments. This ensures precise measurement even when working with full rotations around a circle.

Which image formats work best with the protractor?

PNG, JPG, and WebP formats work best, especially with clear, high-contrast images. Low-contrast images may reduce measurement accuracy, and animated GIFs will display only the first frame.

Can I measure angles on a blank canvas?

Yes, you can use the protractor on the blank white background without uploading an image. This is useful for learning the tool or for general angle reference needs.