ラジアン度変換

What does this tool do

The Radian Degree Converter converts between radians and degrees instantly. Enter an angle value in either unit; the tool displays the equivalent in the other. You can choose the number of decimal places (0–10) for the result. Essential for trigonometry, math, physics, and engineering when working with angles in different representations. All computation runs entirely in your browser.

How to use it

1. Select mode — Choose "Degrees → Radians" to convert from degrees to radians, or "Radians → Degrees" for the reverse.
2. Set decimal places — Select how many decimal places you want in the result (0–10). Default is 6.
3. Enter input — Type a numeric angle. Examples: for degrees use 180 or 90; for radians use 3.14159 or 1.5708.
4. View output — The converted value appears instantly. Copy with one click.
5. Sample or clear — Use Load sample to try an example (180° or π rad), or Clear to reset.

How it works

Degrees to radians: radians = degrees × (π / 180). One full rotation (360°) equals 2π radians. Radians to degrees: degrees = radians × (180 / π). The tool uses JavaScript's Math.PI (≈3.141592653589793) for the conversion. Input is validated: empty, non-numeric, and infinite values are rejected. Maximum input length is 100 characters.

All computation runs entirely in your browser. No data is sent to any server.

Use cases & examples

• Trigonometry — Convert angles between degrees (e.g. 30°, 45°, 90°) and radians for use with Math.sin, Math.cos, etc., which expect radians.
• Physics — Angular velocity, phase angles, and wave equations often mix degrees and radians.
• Education — Teach or learn the relationship between degrees and radians; understand that π rad = 180°.
• Programming — Many APIs use radians; convert user input in degrees to radians before calling trig functions.

Examples

Degrees → Radians:

• 180 → 3.141592653589793 (π)
• 90 → 1.5707963267948966 (π/2)
• 360 → 6.283185307179586 (2π)
• 57.2958 → ~1 radian

Radians → Degrees:

• 3.14159 → ~180
• 1.5708 → ~90
• 6.28319 → ~360
• 1 → ~57.2958°

Limitations & known constraints

• Number precision — JavaScript's Number type has about 15–17 significant digits. Very long decimal strings may lose precision.
• Input length — Maximum 100 characters to avoid performance issues.
• Infinity & NaN — Not supported; the tool rejects non-finite values.
• Symbol π — The placeholder shows "π" as an example; actual input must be numeric (e.g. 3.14159). The tool does not parse the Greek letter π.