About TheProtractor.com
Precision Digital Angle Measurement for Modern Web Browsers
The Protractor (TheProtractor.com) is a free, engineering-grade online angle measurement utility built to replace clunky, low-resolution virtual protractors with a responsive, mathematically rigorous browser instrument.
Our Mission
Whether you are a geometry student checking homework diagrams, an architect verifying roof pitch on a floor plan, a mechanical engineer inspecting CAD screenshots, or a woodworker measuring a physical miter joint against your phone screen, measuring an angle should take seconds—not a software installation.
We designed TheProtractor.com to work immediately on any desktop, tablet, or smartphone with zero registration, zero watermarks, and complete respect for your privacy.
What Sets The Protractor Apart
64-Bit Vector Angle Engine
Unlike static image-overlay protractors, our engine computes exact vector angles using double-precision floating-point trigonometry with configurable precision up to 4 decimal places in Degrees (°), Radians (rad), and Gradians (gon).
Full-Screen Mobile Edge Measurement
Snap the 180° protractor flush to the Bottom, Top, Left, or Right edge of your screen in Full-Screen mode. Place your smartphone edge directly against a physical surface or slope and swing Ray B to read the real-world angle.
Independent Image Upload & Scaling
Upload photos, blueprints, or worksheets in JPG, PNG, or WEBP format. Images automatically scale to fit your workspace and can be dragged, resized from any corner, rotated, or locked independently of the protractor.
100% Client-Side Privacy
Your images and measurements never leave your device. Every calculation, canvas render, and PNG/JPG export happens locally inside your web browser with zero server uploads and zero third-party tracking scripts.
Built for Classrooms, Studios & Workshops
- Students & Educators: Teach and verify acute, right, obtuse, straight, and reflex angles, along with complementary, supplementary, and explementary angle relationships on interactive whiteboards or tablets.
- Engineers, Architects & Designers: Measure angles on technical drawings, elevation diagrams, typography specimens, and UI layouts with multi-angle annotations and high-resolution image export.
- DIY Makers, Carpenters & Craftsmen: Use full-screen edge docking on a mobile phone as a quick pocket bevel gauge or reference protractor on the workbench.
- Biomechanics & Physical Therapy: Measure joint angles and posture alignment directly on locally loaded photographs without uploading sensitive client photos to the cloud.
Open Standards & Accessibility Commitment
TheProtractor.com is engineered to meet WCAG AA contrast guidelines in both Light and Dark themes, supports full keyboard navigation (arrow-key nudging, zoom shortcuts, undo/redo), and provides live ARIA screen-reader announcements for measured angles.