Cosine Calculator

This cosine calculator works out the cosine of any angle you enter, in either degrees or radians, and shows the angle in both units so you can double-check your input. Cosine is one of the six trigonometric functions: in a right triangle it is the ratio of the side adjacent to the angle over the hypotenuse, and on the unit circle it is the x-coordinate reached by rotating through that angle. Type your angle into the single input field, choose degrees or radians from the dropdown, and the result updates instantly as you type. The main result box shows the cosine value rounded to six decimal places, with the angle repeated in radians and in degrees underneath so you can see exactly what was calculated. Internally the calculator always converts your angle to radians before evaluating cosine, since that is the unit the underlying maths uses, then rounds the answer for display. Because cosine is periodic, angles that differ by a full 360 degrees, or 2 pi radians, always return the same value, so different-looking angles can give identical results. Use this tool for trigonometry and geometry homework, physics and engineering work, surveying, navigation, or any time you need an accurate trig value without hunting for a scientific calculator. A worked example, the formula and the assumptions behind the calculation are set out further down the page.

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Angle

Angle unit

Angle (radians)

Angle (degrees)

The formula

Cosine is the ratio of the side adjacent to the angle to the hypotenuse in a right triangle, and the x coordinate on the unit circle. The calculator computes cos of the angle in radians.

Worked example

Cosine of 60 degrees is 0.5. Enter 60 with degrees selected to confirm, then try 0 degrees to get 1.

Frequently asked questions

How do I find the cosine of an angle?

Enter the angle and pick degrees or radians. The calculator converts to radians and evaluates the cosine.

Degrees or radians?

Either. Choose the unit in the dropdown. The angle is shown in both units beside the result so you can check.

Why is the result the same every 360 degrees?

The trig functions are periodic. Sine and cosine repeat every 360 degrees (2 pi radians), so equivalent angles give the same value.

Who this calculator is for

This calculator is for students, engineers, surveyors and anyone who needs the cosine of an angle.

What this calculator assumes

You enter a single angle in the chosen unit.
The angle is converted to radians for the calculation.
Results are rounded for display.

Formula and sources

Related calculators

Trig Calculator: all six trig functions at once.
Degrees to Radians Calculator: convert angle units.
Right Angle Triangle Calculator: solve a right triangle.

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