How many radians is 180 degrees?

π radians, approximately 3.14159 radians.

Where are gradians used?

In surveying and civil engineering, where a right angle is divided into 100 units.

They are the natural unit for trigonometry and calculus: 180° = π rad, so 90° = π/2 and 360° = 2π rad.

Where are gradians used?

They split a right angle into 100 decimal parts and appear in European surveying. 100 grad = 90°.

📐 Angle Converter

Convert degrees, radians, gradians and more instantly.

How it works

Type a value in the left field.
Pick the units to convert from and to.
The result updates instantly, with a full reference table below.

Key units & conversion basis

Angle units are converted through degrees (°). Math and physics use radians, some European standards use gradians, and surveying or military optics use mils.

Unit	Symbol	In degrees	Common use
Degree	°	1°	general
Radian	rad	57.2958°	math, physics
Gradian	grad	0.9°	right angle = 100 grad
Turn	turn	360°	full rotation
Arcminute	′	1/60°	geodesy, astronomy
Arcsecond	″	1/3,600°	precision
Mil (NATO)	mil	0.05625°	military optics

🧮 How the conversion is calculated

A radian is the angle where arc length equals radius, so 180° = π rad. Example: 45° to radians → 45 × π/180 = 0.7854 rad.

🎯 When to use this

Convert degrees to radians for trigonometry and engineering
Check angle units on CAD or design drawings
Convert arcminutes/arcseconds for astronomy and navigation
Convert radian values used in math and programming back to degrees

📖 Guide: Converting Degrees to Radians — Avoiding Trig & Coding Mistakes →

Frequently Asked Questions

How many radians is 180 degrees?: π radians, approximately 3.14159 radians.
Where are gradians used?: In surveying and civil engineering, where a right angle is divided into 100 units.
Why use radians?: They are the natural unit for trigonometry and calculus: 180° = π rad, so 90° = π/2 and 360° = 2π rad.
Where are gradians used?: They split a right angle into 100 decimal parts and appear in European surveying. 100 grad = 90°.