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Measured AngleAcute
45.00°(Outer: 135.00°)
Ready: Drag angle arm handle or vertex to measure. Output updates continuously.
Photo & Blueprint Overlay
Image Protractor Tool
Upload or paste any image (Ctrl+V) to measure interior and exterior angles directly over photos.
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STEP 1
Move center circle to angle corner, then rotate arm to match edge.
Angle45.0°
Angle45.0°
✨Detected dominant edge at ~45.0°
1. Upload Image→2. Drag Center to Corner→3. Align Arm with Edge→4. Read Angle
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Comprehensive Geometry & Engineering Handbook
Online Free Protractor & Screen Ruler · onlinefreeprotractor.com
✓ 100% Client-Side Private · Local RAM
⠿📏 Screen Ruler
Dist: 0.00 cm📸
Measure Angles on Any Image or PDF
Drag and drop an image or blueprint here, press Ctrl+V to paste, or browse your files.
100% Client-Side Privacy: No images are uploaded to any server.
Drag Blue Center to vertex · Drag Arm Handle to rotate
⠿💳 Card
85.60 × 53.98 mmScale: 100 px = 10.0 cm
Bubble Level
MEASURED ANGLE OUTPUT
45.00°
ACUTE
Outer: 135.00° · 0.7854 rad
Supplementary
135.00°
Complementary
45.00°
Trigonometric Ratios
sin: 0.7071 · cos: 0.7071
Device Calibration
113.0 PPI · 1:1 Scale
RECORDED ANGLE PINS
| # | Angle (Deg) | Radians | Type |
|---|
Primary ScaleInner Scale
45.00°Acute
Outer Scale135.00°
Angle Relationships
Supplementary (180°-θ):135.00°
Complementary (90°-θ):45.00°
Reflex (360°-θ):315.00°
Trigonometric Values
sin(θ):0.7071
cos(θ):0.7071
tan(θ) (Slope):1.0000
Circle Geometry
Arm Radius:200 px
Arc Length:157.08 px
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Recorded Measurements0 Pins
| # | Label | Degrees | Radians | Class | Action |
|---|---|---|---|---|---|
| No pinned angles yet. Click canvas to place ray pins or click "+ Save Reading". | |||||
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How-To Guide
How to Measure Angles on Any Photo
Follow these 3 simple steps to load an image, align vertices, and calibrate real-world dimensions.
01
Load Your Photo or Diagram
Click Upload Image or press Ctrl+V to paste a screenshot directly from clipboard.
Supports JPG, PNG, WebP, SVG
02
Calibrate Real Dimensions
Click Calibrate Scale, click two points of a known length (e.g. 10 cm ruler mark), and enter the real value to get instant millimeter/inch readouts.
Units: cm, mm, in, m, px
03
Measure Angles & Radii
Drag the protractor center to the vertex and align the ray arms. Read degrees, radians, and arc lengths instantly.
Instant On-Screen Readout
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Image Protractor Help
Image & Photo Protractor FAQs
Common questions about measuring angles in photos, pasting images, scale calibration, and blueprint analysis.
How do I paste a screenshot or image directly without saving to disk?↓
Simply take a screenshot using your operating system shortcut (Win+Shift+S or Cmd+Shift+4), click anywhere on this webpage, and press Ctrl+V (or Cmd+V). The image will instantly appear on the canvas stage.
Are my uploaded images or blueprints uploaded to an external server?↓
No. All image processing, opacity adjustments, and coordinate calculations are performed 100% locally in your browser's RAM using the HTML5 Canvas API. Your pictures and proprietary blueprints never leave your device.
How does the 2-point real-world length calibration work?↓
Click Calibrate Scale and pick two points on an object of known length in your photo. Type the physical dimension. The tool calculates the exact pixel-to-unit ratio, allowing ray lengths to display in true centimeters, millimeters, or inches.
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Can I adjust photo opacity or rotate the picture?↓
Yes. The toolbar includes an Opacity Slider (10% to 100%), 90° Clockwise Rotation, Horizontal Flip, Fit Screen, and Fill Width buttons to position your reference image comfortably behind the protractor.
What image formats are supported?↓
The image protractor supports all standard web raster and vector formats, including PNG, JPG/JPEG, WebP, SVG, GIF, and BMP.