Choose overlay mode to drag a virtual dial onto your screen, or point mode to click three points and get an instant reading. This online protractor gives you two ways to measure an angle. In overlay mode, drag a full 360° protractor onto your image or canvas, rotate it to line up with the edge you're measuring, and read the angle straight off the dial. In point mode, click a vertex and then two points along each ray, and the angle is calculated for you automatically — no aligning a dial required. Both modes work directly in your browser, on desktop or mobile, with no download needed.

Line up the protractor's center point with the vertex of the angle, align one ray with the 0° line, then read the degree mark where the second ray crosses the scale. That's the classic method with a physical protractor, and it's exactly what overlay mode replicates on-screen: the center of the dial is your vertex, and rotating it aligns the 0° edge with your reference line. If you'd rather skip manual alignment altogether, point mode does the same measurement for you automatically — just click the vertex and the two rays, and the angle is calculated instantly. It's a good way to learn the concept and get a precise reading at the same time.

Most protractors print two scales — one running 0–180° clockwise, the other counter-clockwise — and you always read the scale that starts at 0° on the ray you're measuring from. This is the single most common source of confusion when learning to use a protractor: since both scales appear on the same dial, it's easy to read the wrong number and get an angle that's off by several degrees or reversed entirely (e.g. reading 40° instead of 140°). The rule is simple — find which scale has "0" sitting on your first ray, and follow that same scale around to your second ray. This online protractor sidesteps the problem entirely: in point mode, the angle is calculated from your clicked points automatically, so there's no dual-scale reading to get wrong in the first place.

A protractor can measure any angle from 0° to 360°, which are grouped into acute, right, obtuse, straight, and reflex angles. An acute angle is less than 90°, a right angle is exactly 90°, an obtuse angle is between 90° and 180°, and a straight angle is exactly 180°. Anything greater than 180° is a reflex angle — the angle measured on the outside of two rays rather than the inside. This tool identifies and labels the angle type automatically as you measure, and includes a dedicated reflex option so you can read the outside angle with one click instead of subtracting it from 360° by hand.

The most common protractor errors are misreading the inner vs. outer scale, not lining the center point up exactly with the vertex, and letting the protractor shift slightly while reading the angle. Any small misalignment at the vertex gets magnified into a noticeably wrong reading, especially on smaller angles. A digital protractor online removes two of these error sources by design: there's no dual scale to misread, since the angle is calculated for you, and nothing can physically slip while you're reading it — the measurement stays locked to the points or dial position you set.

Use it the same way as a physical protractor — line up the vertex and read the degree — but with automatic, error-free readings, which makes it well suited to checking homework and classroom demonstrations. This online protractor tool for students works for identifying angle types, measuring diagrams straight out of a textbook or worksheet photo, and verifying answers before handing in homework. Teachers can project it for a live demonstration, and students can use it independently to self-check geometry exercises without needing a physical protractor on hand.

Draw a straight baseline, place the protractor's center on one end of it, find your target degree mark on the scale, mark a point there, then draw a line connecting the baseline's endpoint to that mark. This method works for any angle you need — 50°, 75°, 100°, 320°, or anything in between; for angles over 180°, measure the reflex angle on the outside instead of the interior. If you're working digitally rather than on paper, you can use this tool's overlay mode to line the dial up with an angle you've already drawn and confirm it's accurate, or use point mode to place your intended angle precisely and read back the exact degree as you adjust it.

Yes — this online protractor works fully in your phone's browser, so you don't need a dedicated app to measure angles on the go. It's fully responsive, meaning the same overlay and point-mode measuring tools work whether you're on a phone, tablet, or desktop, with no install required. This makes it a practical stand-in for a physical protractor when you're away from your pencil case — measure an angle on a photo, a worksheet, or anything else your camera can capture.

Yes — protractors remain a core part of geometry curricula, and measuring and constructing angles by hand is still a standard skill taught in schools. What's changed is the format: many students and teachers now use a digital protractor online alongside, or instead of, a physical one, especially for homework done on a computer or tablet, or for checking work quickly without digging one out of a pencil case. The underlying skill — reading and constructing angles accurately — hasn't gone anywhere.

A right angle is exactly 90°, not 180°. 180° is a straight angle — a straight line, with no bend at all. A right angle is the angle you see at the corner of a square or a piece of paper, and it's the halfway point of a straight angle. This tool labels the angle type automatically as "right" whenever a measurement lands at (or very close to) 90°, so you don't need to remember the exact cutoffs yourself.

No — measuring an angle with a protractor is a simple three-step process once you know to line up the center point and read the correct scale, and most of the difficulty people run into is the dual-scale reading mistake, not the concept itself. This online protractor makes it even easier for beginners, since point mode removes the scale-reading step entirely — just click the vertex and two rays, and the exact angle is calculated and displayed for you.