Use a half turn as your reference
180° is π radians. This gives the conversion factor π/180 radians per degree.
Simplify before using a decimal
60° × π/180 = π/3 radians. 270° × π/180 = 3π/2 radians. Exact multiples of π are often clearer than rounded decimals.
Reverse the conversion
To go from radians to degrees, multiply by 180/π. For example, π/4 radians × 180/π = 45°. Check your calculator’s angle mode before using trigonometric functions.