The fastest and easiest online protractor
Measure angles online.
Open the tool, drag the arms, and get the accurate live angle immediately. Upload custom diagrams, paste screenshots from clipboard, or calibrate your screen. Fully offline-capable and privacy-friendly.
Drag & Drop or Paste an Image
Paste directly using Ctrl+V / Cmd+V, drop a file, or click 'Upload Image' above. Measuring works immediately!
Geometry & Education Mode
Angle Classification
An angle is formed when two straight lines or rays meet at a shared endpoint called the **vertex**. Here, the protractor center is placed on the vertex to measure the angular rotation from the base line.
Related Trigonometry
Trigonometry outputs are computed relative to the base line. Complementary angles sum up to 90°, and supplementary sum up to 180°.
Live Measured Angle
Screen Calibration96 DPI
We query your system's hardware configurations and device pixel ratios to auto-estimate screen size.
Enter your screen's physical diagonal size in inches to calculate exact pixels-per-inch (PPI).
Formula: DPI = √(width² + height²) / diagonal
Hold a physical credit card against your screen and adjust the slider until the on-screen card matches the physical card.
Standard card size: 3.37 inches (85.6mm) wide.
Protractor Options
Load Demo Worksheet
Measurement History
No saved measurements yet.
Geometry Calculators
Solve triangle dimensions based on the active measured angle $\theta$.
How to measure angles using an online protractor.
An **online protractor** is a digital instrument designed to measure angles directly in your web browser. Unlike a physical tool made of plastic or metal, a virtual protractor works dynamically on images, PDF diagrams, architectural drawings, or geometric shapes.
Set your Vertex
Align the central origin target of the protractor (the vertex) directly over the corner or intersection where your two lines meet. Drag the center crosshair handle to position it.
Align the Baseline
Drag the **Base Arm (A)** along the first line of your angle. The protractor circle automatically rotates and locks its zero-degree mark ($0^\circ$) to this starting direction.
Measure the Angle
Drag the **Measuring Arm (B)** along the second line. The live angle displays instantly in degrees and radians in the dashboard, alongside slope pitch and trigonometry.
Key features of this tool
Frequently Asked Questions
How do I paste an image directly from my clipboard?
Simply select this browser page tab, copy any image screenshot (using e.g. Snipping tool or print-screen) to your clipboard, and press **Ctrl + V** (or **Cmd + V** on Mac). The image will load instantly.
Why calibrate with a credit card?
Every screen has a different physical density (DPI). By adjusting the on-screen box to match a standard physical object like a credit card (which is exactly 3.37 inches wide), we establish an exact pixels-per-inch scale factor.
Can I measure complementary and supplementary angles?
Yes. The control panel automatically displays supplementary angles ($180^\circ - \theta$) and complementary angles ($90^\circ - \theta$) in real-time, making it useful for geometry homework and engineering reports.
Does this online protractor support 360 degrees?
Yes. You can toggle between 180° (semicircle) and 360° (full circle) mode inside the **Protractor Options** menu in the sidebar.
Online Protractor: The Free, Accurate Angle Measurement Tool
Our online protractor is the most accurate online protractor available today. Designed as a comprehensive online protractor tool, it helps students, teachers, engineers, and architects measure angles directly in their web browser without downloading any software. Whether you need an online protractor for kids or a professional-grade online protractor angle finder, our tool delivers precision and ease of use.
Why Choose Our Free Online Protractor?
Finding a reliable free online protractor can be challenging. Many tools are inaccurate, cluttered with ads, or require installation. Our online protractor interactive tool solves these problems by providing a clean, fast, and accurate online protractor experience. Here is why thousands of users trust our online protractor free tool:
Precision Angle Measurement
Our online protractor tool displays angles in real-time with decimal-point accuracy. Measure acute, obtuse, right, straight, and reflex angles instantly. The online protractor 360 mode allows you to measure full rotations, making it perfect for geometry, trigonometry, and engineering applications.
Interactive Online Protractor Experience
This is not just a static image. Our interactive online protractor lets you drag measurement arms, rotate the protractor, and adjust its size. The online protractor overlay feature lets you place the tool over any image for seamless angle measurement on diagrams, blueprints, and photographs.
Online Protractor for Students and Education
Our online protractor tool for students is designed with education in mind. Teachers use it for classroom demonstrations, while students rely on it for online protractor practice sessions. The online protractor app works perfectly on tablets and laptops, making it ideal for remote learning and homework help.
The built-in online protractor drawing tool feature lets you visualize geometric concepts. Students can practice measuring angles on uploaded images, learn about complementary and supplementary angles, and understand trigonometric relationships through our interactive online protractor angle finder.
Advanced Features of Our Online Protractor Tool
How to Use This Free Online Protractor
Getting started with our free online protractor tool for students and professionals is simple. Follow these three easy steps:
Upload or Paste Image
Upload a photo, paste from clipboard, or use our online protractor camera to capture an image. You can also load the built-in blueprint grid.
Position the Protractor
Drag the vertex point to your angle's corner. Align the baseline arm along one side of the angle. Use keyboard shortcuts for precision.
Measure the Angle
Drag the measuring arm to the second line. The online protractor angle finder displays the angle in degrees and radians instantly.
Who Uses Our Online Protractor?
Our online protractor interactive tool serves diverse users across multiple fields:
- Students & Teachers: Perfect for online protractor practice, geometry lessons, and homework assignments
- Engineers & Architects: Measure angles on blueprints, floor plans, and technical drawings
- Woodworkers & Craftsmen: Use the online protractor and angle maker for precise cuts and joints
- Photographers: Analyze composition angles in images using the online protractor overlay
- DIY Enthusiasts: Quick angle measurements for home improvement projects
Start Measuring Angles Online Now
Experience the most accurate online protractor available. Our free online protractor works on all devices - desktop, tablet, and mobile. No registration required. No data collected. Simply open the tool and start measuring angles with confidence.
Try the Online Protractor Free