Online Protractor
Measure angles on your screen from 0° to 360° with draggable arms and 0.1° resolution.
How to Use the Online Protractor
Align the center pivot crosshair of the protractor with the vertex (corner) of the angle you wish to measure.
Keep the dashed baseline aligned with your reference edge or drag its handle to match your drawing orientation.
Drag the orange measurement arm to the second ray. Read the live angle in degrees, radians, and supplementary values.
Looking for linear measurement or coordinate distances? Explore our Online Ruler, use the 3-Point Angle Tool, or measure lengths on photos with our Image Ruler.
Frequently Asked Questions About the Online Protractor
Answers on angle measurement precision, mobile goniometers, and drafting accuracy.
What is an online protractor?▼
An online protractor is an interactive web-based drafting instrument that allows you to measure and plot angles directly on your screen. It features full 0–360° and 180° half-circle modes with dual inner and outer scales, draggable measurement arms, and high-precision 0.1° readouts.
How do I measure an angle on screen?▼
Place your physical object or diagram against your screen, align the central pivot crosshair with the vertex of the angle, position the base arm along the baseline, and drag the orange indicator arm until it aligns with the second ray. The digital readout immediately displays the interior angle, supplementary angle, reflex angle, and radians.
Can I adjust the angle using arrow keys?▼
Yes. Click or tap into the protractor to focus it, then use the Left and Right Arrow keys for fine 0.1° increments. Hold Shift while pressing Arrow keys for 1.0° steps, or use Alt for 5.0° steps.
Does the online protractor work on mobile phones?▼
Yes. The protractor uses touch-action optimization and pointer events, allowing smooth rotation and drag gestures on iPhone, iPad, and Android screens without unwanted page scrolling.