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.

Calculate.co.nz is proud to be partnered with Premium Homes, a recognised leader in eco-friendly, sustainable, and energy-efficient homebuilding. With a dedicated team and award-winning experience, they create homes that prioritise health, comfort, and long-term performance. Their founders, Andrew and Kelly, set out to raise the standard of residential construction in New Zealand by combining practical building expertise with a clear commitment to doing things better for homeowners.