Degree to Radian Converter

Convert degrees to radians instantly with interactive unit circle visualization, step-by-step formulas, common angle references, and bidirectional conversion support.

Free to useNo sign-up requiredUpdated Jan 2026

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Common Angles

Angle in Degrees

Decimal Precision

Output Format

Embed Degree to Radian Converter Widget

About Degree to Radian Converter

Welcome to the Degree to Radian Converter, a precision tool for converting angle measurements between degrees and radians. Featuring an interactive unit circle visualization, step-by-step formula breakdowns, and support for both decimal and pi-fraction output formats, this converter is designed for students, engineers, scientists, and anyone working with angular measurements.

Understanding Degrees and Radians

Degrees and radians are two different units for measuring angles. While degrees divide a full circle into 360 equal parts, radians measure angles based on the relationship between an arc length and the radius of a circle.

The fundamental relationship between these units is:

Fundamental Relationship

$$180° = \pi \text{ radians}$$

This means a complete circle (360°) equals 2π radians, and a right angle (90°) equals π/2 radians.

Degree to Radian Conversion Formula

To convert an angle from degrees to radians, use the following formula:

Conversion Formula

$$\text{radians} = \text{degrees} \times \frac{\pi}{180}$$

Why Use Radians?

Radians are the preferred unit in mathematics and physics because they simplify many calculations:

Calculus: The derivative of sin(x) equals cos(x) only when x is in radians
Arc Length: s = rθ (arc length equals radius times angle in radians)
Angular Velocity: ω = θ/t works directly with radians
Taylor Series: Trigonometric expansions use radians

Common Angle Conversions

Here are the most frequently used degree to radian conversions:

Degrees	Radians (π form)	Radians (decimal)
0°	0	0
30°	π/6	0.5236
45°	π/4	0.7854
60°	π/3	1.0472
90°	π/2	1.5708
120°	2π/3	2.0944
135°	3π/4	2.3562
150°	5π/6	2.6180
180°	π	3.1416
270°	3π/2	4.7124
360°	2π	6.2832

How to Use This Converter

Enter your angle: Type the degree value in the input field, or click one of the common angle buttons for quick access.
Select precision: Choose how many decimal places you want in the result (2-15).
Choose output format: Select decimal, pi fraction, or both representations.
View results: See the converted value along with the interactive unit circle showing the angle position, quadrant, and trigonometric values.

Understanding the Unit Circle

The unit circle is a circle with radius 1 centered at the origin. It provides a visual way to understand angles and trigonometric functions:

Angle measurement: Angles start from the positive x-axis (0°) and increase counterclockwise
Coordinates: For any angle θ, the point on the unit circle has coordinates (cos θ, sin θ)
Quadrants: The circle is divided into four quadrants, each with different sign combinations for sine and cosine

Quadrant Reference

Quadrant I (0°-90°): Both sine and cosine are positive
Quadrant II (90°-180°): Sine positive, cosine negative
Quadrant III (180°-270°): Both sine and cosine are negative
Quadrant IV (270°-360°): Sine negative, cosine positive

Applications

Mathematics and Calculus

Radians are essential for calculus operations involving trigonometric functions. The limit identities and derivatives only work correctly with radian measure.

Physics and Engineering

Angular velocity, rotational motion, wave functions, and oscillations all use radians. Converting between degrees (often used in measurements) and radians (used in formulas) is a common task.

Computer Graphics

Most programming languages and graphics libraries use radians for rotation functions. Converting user-friendly degree inputs to radians is essential for 2D and 3D transformations.

Navigation and Geography

Calculating distances on Earth using latitude and longitude requires converting degrees to radians for spherical trigonometry formulas.

Frequently Asked Questions

What is the formula to convert degrees to radians?

To convert degrees to radians, multiply the angle in degrees by π/180. The formula is: radians = degrees × (π/180). For example, 90° = 90 × (π/180) = π/2 radians ≈ 1.5708 radians.

Why do we use radians instead of degrees?

Radians are used in mathematics and physics because they simplify many formulas. When using radians, the derivative of sin(x) is simply cos(x), arc length equals radius times angle (s = rθ), and many calculus formulas become cleaner. Radians represent the ratio of arc length to radius on a unit circle.

What is 180 degrees in radians?

180 degrees equals π radians (approximately 3.14159 radians). This is the fundamental relationship between degrees and radians: a straight angle of 180° corresponds to exactly π radians, which represents half a circle.

What are the most common angle conversions from degrees to radians?

Common conversions: 30° = π/6 rad, 45° = π/4 rad, 60° = π/3 rad, 90° = π/2 rad, 120° = 2π/3 rad, 180° = π rad, 270° = 3π/2 rad, 360° = 2π rad. These angles appear frequently in trigonometry and geometry.

How many radians are in a full circle?

A full circle contains 2π radians (approximately 6.28318 radians). This is equivalent to 360 degrees. The circumference of a unit circle is 2π, which is why one complete rotation equals 2π radians.

Related Conversions

Radian to Degree Converter - Convert radians back to degrees

Additional Resources

Reference this content, page, or tool as:

"Degree to Radian Converter" at https://MiniWebtool.com/degree-to-radian-converter/ from MiniWebtool, https://MiniWebtool.com/

by miniwebtool team. Updated: Jan 27, 2026

Developer API available: Run this tool from your app, automation, or agent with one JSON HTTP request. View API docs

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