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How to Use the Online Protractor Tool

Follow this simple step-by-step guide to measure angles accurately on any image or directly on your screen.

📹

Watch Quick Start Guide (2 min)

New to the tool? Watch this quick video to get started instantly.

▶ Watch Video Tutorial
1

Upload Your Image

Start by uploading the image you want to measure angles on. The tool supports all common image formats.

  • Click the "Choose File" or "Upload Image" button on the tool
  • Select your image file (JPG, PNG, GIF, WEBP, SVG supported)
  • You can also drag and drop your image directly onto the canvas
  • For best results, use high-resolution images with clear lines
💡 Pro Tip: No image? You can measure directly on the blank canvas using the protractor overlay.
2

Position the Protractor

Move the protractor so its center point is exactly at the vertex (corner) of the angle you want to measure.

  • Use the Center X and Center Y sliders to position the protractor
  • Or click and drag the protractor directly on the canvas
  • Adjust the Radius slider to make the protractor larger or smaller
  • The red crosshair marks the exact center point
💡 Pro Tip: Zoom in on your image for more precise positioning of the center point.
3

Rotate & Align

Rotate the protractor to align its baseline with one side of your angle.

  • Use the Rotation slider to rotate the protractor clockwise or counter-clockwise
  • Watch the 0° mark on the protractor - this is your baseline
  • Align the baseline perfectly with one side of the angle you're measuring
  • Use the Quick Angle buttons (30°, 45°, 90°, 120°, 180°) for common angles
💡 Pro Tip: The degree marks on the protractor help you visually align with the angle sides.
4

Measure the Angle

Click on the canvas to place measurement points and get instant angle readings.

  • Click anywhere on the canvas to place a measurement point
  • The tool automatically draws a line from the center to your point
  • The angle measurement appears above the point and in the top badge
  • Add multiple points to measure different angles on the same image
💡 Pro Tip: Click multiple points to compare different angles or verify measurements.
5

Save & Export

Save your measurements or export the canvas for documentation.

  • Click "Export Canvas" to save your measurement as a PNG image
  • The exported image includes all points, lines, and angle labels
  • Clear all points with the "Clear Points" button to start fresh
  • Reset the protractor position with "Reset Protractor" button
💡 Pro Tip: Export your measurements to share with team members or include in reports.

Understanding the Display

📐 Live Angle Display

The top badge shows your current angle measurement in real-time. It updates as you add or remove measurement points.

📊 Complementary & Supplementary

Below the canvas, you'll see auto-calculated complementary (90° - angle) and supplementary (180° - angle) values.

📈 Slope Percentage

The tool automatically converts your angle measurement to slope percentage, useful for construction and engineering work.

📍 Points List

The sidebar shows all your measurement points with their angles. Click the ✖ button to remove any point.

Customization Options

🎨 Colors

Customize the protractor appearance with color pickers for lines, outer circle, inner circle, and measurement points.

📏 Size & Position

Adjust the protractor radius and center position using the sliders for perfect alignment with your image.

🔄 Rotation

Fine-tune rotation using the slider or use quick angle buttons for common measurements.

Keyboard Shortcuts

Reset Position
Click "Reset Protractor" button
Clear All Points
Click "Clear Points" button
Export Canvas
Click "Export Canvas" button
Quick Angles
Use the preset buttons (30°, 45°, 90°, etc.)

Still Have Questions?

Check our detailed tutorial or contact our support team for assistance.

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