Angle Finder & Virtual Protractor
Accurately measure angles on screen, over photos, or live through your camera stream.
Angle Properties & Complementary
Keyboard Shortcuts:
How to Use Angle Finder Protractor
Learn how to use angle finder protractor on screen, over uploaded images, or live through your mobile camera stream with sub-pixel vector accuracy.
1. On-Screen Virtual Protractor
Overlay a semi-transparent 180° or 360° digital protractor directly over any web page, document, or diagram. Drag the center vertex V and rotate rays A and B to measure any corner or angle.
2. Upload Photo or Blueprint
Upload architectural blueprints, geometric homework diagrams, or construction photos (PNG/JPG). Pan and pinch-to-zoom images under the protractor to calculate precise structural angles.
3. Live Mobile Camera (WebRTC)
Stream live video directly from your smartphone or laptop camera. Superimpose digital measuring lines over physical objects (woodwork, roof pitches, tiles, pipes) and freeze frame for easy reading.
How to Read a Protractor Angle Finder
Understanding how to read a protractor angle finder requires aligning the center origin (vertex V) with the vertex point of the angle you wish to measure.
- • Align Base Ray A: Drag Ray A along the baseline of your geometric shape or horizontal reference.: Drag Ray A along the baseline of your geometric shape or horizontal reference.
- • Rotate Angle Ray B: Drag Ray B to line up with the intersecting edge or slope line.: Drag Ray B to line up with the intersecting edge or slope line.
- • Read Multi-Unit Readout: The tool instantly displays the measured angle in Degrees (°), Radians (rad), and Slope Percentage (%).: The tool instantly displays the measured angle in Degrees (°), Radians (rad), and Slope Percentage (%).
Trigonometric Conversion Formulas
Example: 45° × (3.14159 / 180) = 0.7854 rad
Example: tan(45°) × 100 = 100% slope (1:1 rise over run)
Where to Use an Online Angle Finder
Carpentry & Woodworking
Check miter cut angles, bevel joint angles, and frame squareness by overlaying the digital protractor on wood blueprints or live camera feeds.
Roof Pitch & Architecture
Calculate roof slope percentage (%) and pitch angles from elevation photos or PDF site plans without climbing onto roofs.
Solar Panel Alignment
Determine optimal tilt angles for solar photovoltaic panel mounting racks based on latitude and seasonal sun positions.
Geometry & Engineering
Verify triangle interior angles, vector angles, and CAD drawing dimensions for physics homework or engineering validation.
Angle Reference & Conversion Table
Quick conversion between standard geometric angles, radians, and slope percentages.
| Degrees (°) | Radians (rad) | Slope Percentage (%) | Classification |
|---|---|---|---|
| 0° | 0.000 rad | 0.0% | Zero Angle |
| 30° | 0.524 rad (π/6) | 57.7% | Acute |
| 45° | 0.785 rad (π/4) | 100.0% (1:1) | Acute |
| 60° | 1.047 rad (π/3) | 173.2% | Acute |
| 90° | 1.571 rad (π/2) | Undefined (Vertical) | Right Angle |
| 120° | 2.094 rad (2π/3) | -173.2% | Obtuse |
| 180° | 3.142 rad (π) | 0.0% | Straight Angle |
| 270° | 4.712 rad (3π/2) | Undefined | Reflex Angle |
| 360° | 6.283 rad (2π) | 0.0% | Full Rotation |
Frequently Asked Questions
Everything you need to know about measuring angles online with high precision.