Online Protractor

Measure angles on screen or from uploaded images and camera photos with an interactive 180° / 360° transparent digital protractor. Typical uses include geometry and trigonometry homework and classroom lessons, measuring slope angles on blueprints, CAD drawings, and architectural plans, and analyzing joint angles in sports biomechanics and physical therapy photos. The focused Online Protractor workflow is intended for people who need a dependable result without opening a larger desktop application or creating an account for a one-off task.

Calculates vector trigonometry angles using Math.atan2(dy, dx) across drag handles and renders SVG protractor overlays. Its controls cover interactive 360-degree digital transparent protractor overlay, dual angle readouts: Acute/Obtuse angle and Reflex angle in degrees and radians, upload reference images and drawings for direct angle inspection, and snap to 15°, 30°, 45°, and 90° increments option. The tool accepts ray Arm Points, and Background Image. It produces measured Angle (°) that can be reviewed before it is saved.

Image angle measurement accuracy depends on the resolution and flatness (perspective distortion) of the uploaded photo. When Online Protractor is marked as in-browser, its work remains on the current device; available memory, processor speed, browser support, permissions, and source quality can still affect the result. Keep the original material supplied to Online Protractor until its measured Angle (°) has been checked for the intended use.