Exact
1/2
Sin 30 Degrees
Answer
sin 30° equals 1/2, which is 0.5 as a decimal.
Decimal
0.5
Formula
sin 30° = 1/2 = 0.5
Worked steps
1
Right-triangle definition
In a right triangle, sin(angle) = opposite side ÷ hypotenuse. For a 30°–60°–90° triangle with sides 1 : √3 : 2, the side opposite the 30° angle gives sin 30° = 1/2.
2
Calculator method (DEG mode)
Set the calculator to DEG. Press sin, type 30, press =. Result: 0.5.
3
Calculator method (RAD mode)
Convert 30° to radians first: 30 × π / 180 = 0.523599 rad. Then sin of that gives 0.5.
About this value
Sin 30° is one of the standard angle values memorised in trigonometry. The exact form is 1/2, and the decimal 0.5 is what a scientific calculator returns. This is the smallest standard angle in the 30–60–90 triangle and the easiest sine value to remember.
Frequently asked questions
What is sin 30 degrees?
Sin 30 Degrees equals 1/2 as an exact value, or 0.5 as a decimal. The exact form is what you'd typically write in exam working; the decimal is what your calculator displays.
How do I enter this on a calculator?
Set the angle mode to DEG. Press sin, type the angle, press =. If your calculator is in RAD mode by mistake, you will get a different answer — always check the mode pill before pressing a trig function.
Why memorise the standard angle values?
The values for 30°, 45°, 60°, and 90° appear in almost every trigonometry problem at school level. Knowing the exact form (with surds) lets you produce surd-form answers expected in exams, instead of decimal approximations.
What is this in radians?
To convert the angle to radians, multiply by π/180. The function value is the same regardless of mode — the answer for 30° is 0.5 in DEG or sin(angle_in_rad) of the equivalent radian measure.