How to measure an angle in a picture
- Open your photo. Tap Choose a photo (on a phone you can take a new picture right away), drag a file onto the box, or paste a screenshot.
- Tap three points: the end of the first line, the corner where the lines meet (the vertex), then the end of the second line.
- Fine-tune. Drag any point to adjust it. A magnifier appears above your finger so you can see exactly where the point is. Pinch or scroll to zoom in for pixel-level precision.
- Read the result. The angle appears on the photo and in the list below it, together with the reflex angle. Add more measurements if you need them.
- Save it. Download PNG saves the photo with all measurements drawn on it, ready to share or print.
Lines that do not meet? Switch to 2 lines mode and tap two points on each line. The tool extends the lines and measures the angle where they would cross.
Tips for accurate photo measurements
- Shoot square-on. Hold the camera parallel to the surface you are measuring. Photographing at a slant (perspective) makes angles look bigger or smaller than they are.
- Back up and zoom. Wide-angle lenses bend straight lines near the edges of the frame. Stand farther away and use 2× zoom, keeping the angle near the center of the picture.
- Use long arms. Place the end points as far from the vertex as possible. A one-pixel error matters much less on a long line.
- Check against a known angle. If there is a door frame or tile corner in the shot, measure it first. It should read close to 90°.
What people measure with this tool
Posture, fitness and sports form
Coaches, physical therapists and athletes use side-on photos to check knee angle at the bottom of a squat, hip hinge in a deadlift, elbow angle in a push-up, bike-fit knee extension (often around 140°–150°) or a golfer's spine angle at address. Put the vertex on the joint and the arms along the limbs.
Woodworking and home improvement
Snap a photo of an out-of-square corner, a crown molding joint or a stair stringer, then measure it on the couch instead of on the ladder. Pair it with the miter angle calculator to work out your saw settings, or check a roof in a photo and convert it with the roof pitch calculator.
Geometry homework
Photograph a worksheet or textbook diagram and check your protractor readings. It is also handy for finding angles in real-world objects for math projects: bridges, roofs, ramps and road signs.
Science and engineering
Measure contact angles of droplets, the angle of repose of a sand pile, the launch angle of a projectile from a video frame, or the tilt of a structure in an inspection photo.
Frequently asked questions
Is my photo uploaded anywhere?
No. The photo is opened directly by your browser and drawn on your screen. It is never uploaded to a server, and it disappears when you close the page.
How accurate is measuring an angle from a photo?
The math is exact for the points you place, and the magnifier lets you place points to within a pixel. The real limit is the photo itself: lens distortion and perspective change angles. Shoot straight on (camera square to the surface), step back and zoom in rather than getting close with a wide-angle lens, and keep the object in the middle of the frame.
What is the difference between 3-point and 2-line mode?
Use 3-point mode when the two lines meet at a visible corner: tap the end of one line, the corner, then the end of the other line. Use 2-line mode when the lines do not touch in the picture (for example two edges of a road or the tilt of a pole against the horizon): tap two points on each line and the tool extends them to find the angle between them.
Can I measure posture or joint angles?
Yes. Put the vertex on the joint (for example the knee) and the two end points on the hip and ankle to read the knee angle. For best results, take the photo from the side at hip height with the camera level. This is great for checking squat depth, bike fit or running form, but it is not a medical device.
Can I measure more than one angle on the same photo?
Yes. Keep tapping to add as many measurements as you like. Each one gets its own color and number, is listed below the photo, and is included when you download the annotated PNG.
Which image formats work?
Any image your browser can open: JPG, PNG, WebP, GIF and, in Safari, HEIC photos from an iPhone. You can also paste a screenshot straight from the clipboard.