Comprehensive Screen Protractor Guide
Master high-precision angle measurement, pixel calibration, trigonometric modes, and CAD blueprint analysis.
How to Measure Angles Online
Upload or Choose Sample Image
Drag & drop your blueprint, diagram, or photo into the canvas. You can also pick from pre-loaded architectural and geometric samples.
Select Protractor Mode
Choose 360° Circle for full rotation, 180° Semi for standard baseline angles, 90° Quadrant for corners, or Roof Pitch for rise:run ratios.
Align Vertex & Ray Handles
Drag the central red Vertex handle (V) to the angle vertex. Align Ray A and Ray B along the two bounding lines using the 4x Loupe magnifier.
Read & Log Real-Time Values
Instantly view angles in Degrees, Radians, Gradians, Slope %, and Roof Pitch. Click "Save Angle" to build your exported measurement log.
Smart Features for Engineering, Math & Construction
Full Circle 360°
Semi-Circle 180°
Quadrant 90°
Roof Pitch Converter
In-depth tutorials, geometry guides, construction tips, and sub-pixel mathematics explained.
Sub-Pixel Vector Mathematics & Screen Loupe Precision
Discover how sub-pixel canvas rendering and 4x Loupe scope magnification eliminate human error when measuring fine technical lines.
Blueprint Reading & CAD Geometry Measurement Guide
Step-by-step techniques for architectural blueprints, floor plans, and civil engineering CAD PDF exports.
Understanding Roof Pitch vs. Slope Grade Percentage
A complete handbook for roofers and carpenters converting rise-to-run pitch ratios (e.g. 6:12) to incline degrees.