Online Protractor
Measure angles precisely with our free online protractor. Interactive digital protractor for geometry, math, and design work.
Digital Protractor
Controls
About Angle Measurement
What is a Protractor?
A protractor is a measuring instrument used to measure angles. Our digital protractor provides the same functionality as a physical protractor but with enhanced precision and convenience for online use.
Angle Units
Angles can be measured in different units. Degrees are most common, with a full circle being 360°. Radians are used in advanced mathematics, with a full circle being 2π radians. Gradians divide a circle into 400 parts.
Types of Angles
- Acute Angle: Less than 90° (0° < angle < 90°)
- Right Angle: Exactly 90°
- Obtuse Angle: Greater than 90° but less than 180° (90° < angle < 180°)
- Straight Angle: Exactly 180°
- Reflex Angle: Greater than 180° but less than 360° (180° < angle < 360°)
- Full Angle: Exactly 360°
Common Angle Conversions
| Degrees | Radians | Gradians | Description |
|---|---|---|---|
| 0° | 0 rad | 0 gon | No rotation |
| 30° | π/6 rad | 33.33 gon | One-twelfth circle |
| 45° | π/4 rad | 50 gon | One-eighth circle |
| 60° | π/3 rad | 66.67 gon | One-sixth circle |
| 90° | π/2 rad | 100 gon | Quarter circle (right angle) |
| 120° | 2π/3 rad | 133.33 gon | One-third circle |
| 180° | π rad | 200 gon | Half circle (straight angle) |
| 270° | 3π/2 rad | 300 gon | Three-quarter circle |
| 360° | 2π rad | 400 gon | Full circle |
Frequently Asked Questions
How accurate is the online protractor?
Our digital protractor provides measurements accurate to 0.01 degrees, which is more precise than most physical protractors. You can adjust the precision display in the controls.
Can I measure reflex angles (greater than 180°)?
Yes, our protractor can measure angles up to 360°. Simply position your angle lines to measure any angle including reflex angles.
What's the difference between degrees and radians?
Degrees divide a circle into 360 equal parts, while radians are based on the radius of the circle. One radian equals approximately 57.3 degrees. Radians are commonly used in advanced mathematics and physics.