Online Protractor – Measure Angles in Degrees
Free virtual protractor for measuring angles on your screen. Drag the vertex and both arms, read the angle in degrees and radians, and place the protractor over your own photo — no download, no sign-up.
Measured angle
60.0°
Reflex angle
300.0°
Radians
1.0475
Angle type: Acute (less than 90°) · Drag the red vertex or the A and B handles to measure.
Protractor Settings
DialSnap toFine-tune arm BMeasure Angles on a Photo
Upload a photo, screenshot, drawing, or blueprint, then drag the vertex and arms onto the corner you want to measure. Useful for roof pitches, joinery, physics diagrams, posture checks, and geometry homework.
Your image never leaves your device. It is drawn straight onto the canvas in your browser and is never uploaded to a server.
How to Use the Online Protractor
- Place the vertex — Drag the red centre point onto the corner of the angle you want to measure. The whole protractor dial moves with it.
- Line up arm A — Drag the blue A handle along the first line of your angle. Arm A becomes the zero line of the dial, exactly like the baseline of a physical protractor.
- Line up arm B — Drag the green B handle along the second line. The shaded wedge and the large number show the angle between the two arms in degrees.
- Choose precision — Snap to 5°, 1°, or 0.5° for clean values, or pick Free to measure without snapping. The ±1° and ±0.1° buttons nudge arm B for fine adjustments.
- Switch dial or add a photo — Use the 360° full dial for reflex angles, or upload an image and lay the protractor over a real photo, drawing, or diagram.
About the Online Protractor
The Online Protractor by ToolGenie is a free virtual protractor for measuring angles directly in your browser. Instead of hunting for a plastic protractor in a drawer, you drag a movable vertex and two arms onto any corner and read the angle instantly in degrees and radians.
The dial rotates with arm A, so arm A always sits on zero and arm B lands straight on the answer. That removes the classic mistake of reading the wrong scale on a physical protractor. A shaded wedge marks the angle you are measuring, the reflex angle is shown alongside it, and the tool labels the result as acute, right, obtuse, straight, or reflex.
You can also upload a photo, screenshot, technical drawing, or blueprint and place the protractor over it — handy for roof pitch, furniture joints, camera framing, physiotherapy range of motion, physics vector diagrams, and geometry homework. Everything runs client-side: no login, no install, and your image is never uploaded to a server.
Types of Angles and How to Measure Them
Angles are named by size. The online protractor labels each measurement for you, but here is the quick reference:
- Acute angle (0° – 90°) — Smaller than a right angle. Common in triangles, roof pitches, and letter A shapes. Use the 180° half dial and snap 0.5° for these.
- Right angle (exactly 90°) — A perfect square corner. Snap to 1° and nudge with the fine-tune buttons to confirm a corner is truly square.
- Obtuse angle (90° – 180°) — Wider than a right angle but not a straight line. Think of a reclining chair back or an open laptop lid.
- Straight angle (exactly 180°) — The two arms form a single straight line. Useful for checking that a joint or hinge is fully flat.
- Reflex angle (180° – 360°) — Bigger than a straight line. Switch to the 360° full dial, or simply read the Reflex angle value shown next to the main measurement.
Frequently Asked Questions (FAQ)
How do I measure an angle with this online protractor?
Drag the red vertex onto the corner of your angle, drag the blue A handle along the first line, then drag the green B handle along the second line. The measured angle appears in degrees in the middle of the shaded wedge and in the readout panel below the protractor, along with the value in radians.
Is an online protractor accurate?
Yes. This virtual protractor measures the true geometric angle between the two arms, so it is exact to the pixel and reports one decimal place. Unlike a physical protractor there is no parallax error from viewing the scale at an angle. Use Free snapping plus the ±0.1° buttons when you need the finest reading.
How do I read the inner and outer scale on a protractor?
A physical protractor has two scales, one running 0–180 left to right and one running 0–180 right to left. You read the scale that starts at zero on the arm you lined up with the baseline. This online protractor removes the confusion entirely: the dial rotates so arm A always sits on 0°, and arm B lands directly on the correct reading.
Can I measure angles on a photo or screenshot?
Yes. Use the 'Measure Angles on a Photo' panel to upload an image, then drag the vertex and both arms onto the corner in the picture. It works for roof pitch, furniture and joinery angles, blueprints, X-ray or posture photos, camera framing, and physics diagrams. The image is drawn in your browser and never uploaded to a server.
What is the difference between acute, obtuse, and reflex angles?
An acute angle is less than 90°, a right angle is exactly 90°, an obtuse angle is between 90° and 180°, a straight angle is exactly 180°, and a reflex angle is more than 180° but less than 360°. The tool names the type for you under the readout so you do not have to remember.
How do I convert degrees to radians?
Multiply the degrees by π and divide by 180. For example, 90° × π ÷ 180 = 1.5708 radians. This online protractor shows the radian value next to the degree value automatically, so you never need to do the conversion by hand.
How do I measure a reflex angle over 180 degrees?
Switch the dial to 360° so the full circle of degree marks is drawn, then swing arm B past the straight line. You can also simply read the 'Reflex angle' box, which always shows 360° minus the main measurement. Use the Swap arms button if the wedge is highlighting the wrong side of the angle.
Does this virtual protractor work on a phone or tablet?
Yes. The protractor is fully touch-enabled and responsive, so you can drag the vertex and arm handles with your finger on a phone or tablet. The canvas resizes to fit your screen, and the snap settings make small touch targets easy to place precisely.
Do I need to install an app or create an account?
No. The ToolGenie Online Protractor is completely free, runs entirely in your web browser, and requires no download, no plugin, no sign-up, and no permissions. Nothing you measure or upload is sent to a server.
What is the difference between an online protractor and an online ruler?
A protractor measures angles in degrees; a ruler measures length in millimetres, centimetres, and inches. Use this protractor for corners, slopes, and rotations, and use the ToolGenie Online Ruler when you need actual-size length measurements on your screen. The two tools are often used together on the same drawing.
Tips for Accurate Angle Measurements
- Set the vertex first: Place the red centre point on the exact corner before you touch either arm. Everything is measured from that point.
- Make the arms long: Drag the handles far from the vertex. Longer arms make small pointing errors much less significant.
- Snap for clean values: Use 1° or 5° snapping when you expect a round answer, and Free snapping when you are measuring something real.
- Zoom the photo before uploading: Crop tightly around the corner you care about so it fills more of the canvas and is easier to trace.
- Use Swap arms for the other side: If the shaded wedge covers the wrong side of the angle, tap Swap arms instead of re-dragging both handles.