Reference Angle Calculator (with Coterminal Angles)
Use this free reference angle calculator to find the reference angle of any angle, along with its quadrant and its positive and negative coterminal angles. Works in degrees or radians, with a diagram and steps.
What is a reference angle?
The reference angle is the acute angle between the terminal side and the x-axis. By quadrant: Q1 → θ, Q2 → 180° − θ, Q3 → θ − 180°, Q4 → 360° − θ.
Original price was: $109.99.$54.99Current price is: $54.99.
How to use it
- Choose degrees or radians.
- Enter any angle (positive or negative).
- Press Solve.
Related: the Unit Circle Calculator and more free math calculators.
Frequently asked questions
What are coterminal angles?
Angles that share the same terminal side, differing by full turns: θ + 360°·n (or θ + 2πn).
Original price was: $109.99.$54.99Current price is: $54.99.
Does it work for negative angles?
Yes — it first adds full turns to bring the angle into 0°–360°.
Original price was: $109.99.$54.99Current price is: $54.99.
Degrees or radians?
Both — switch with the unit selector.
Original price was: $27.99.$17.99Current price is: $17.99.
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