Find the angle in your photo.
Choose a photo, put V on the corner, then place A and B along its two edges. The reading is the smaller angle between the two lines, from 0° to 180°. You can also use the starting diagram without a photo.
Place each point precisely
Drag a handle, then use the arrow buttons to move the selected point one screen pixel at a time. With a keyboard, Tab to a handle and use the arrow keys; hold Shift to move ten pixels. Reset restores the handles while keeping your photo. Remove photo returns to the diagram.
A photo angle, not a 3D measurement
This measures the angle in the flat image. Perspective, lens distortion, and how you position the handles can change the result. Photograph a flat object straight on for a closer estimate. The decimal is for fine adjustment, not a guarantee of physical accuracy.
Your photo stays here
Photos are processed in this browser and are not uploaded. Choose a JPEG, PNG, or WebP under 20 MB and 48 megapixels. Large photos are reduced to a maximum edge of 2,400 pixels for responsive editing. HEIC files need conversion to JPEG first.
Save image downloads a PNG with the displayed photo or diagram, the three labeled points, and the measured angle. Your original file is unchanged. Leaving this page clears the photo; switching to another app stops an active drag.
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