# Hemisphere

## Hemisphere

One half of a sphere.

Any plane that passes through the centre of a sphere divides the sphere into two hemispheres.

### Formula

The formula to calculate the total area $$A$$ of a hemisphere of radius $$r$$ is:

$$A=\pi r^{2}+\frac{4\pi r^{2}}{2}=3\pi r^{2}$$.

### Geographic note

In geography, a hemisphere is one half of the Earth. The globe can be divided into two hemispheres, north and south, each of which is centred at a point called a pole and separated from the other by a great circle.

Similarly, the Earth can be divided into the Eastern Hemisphere and the Western Hemisphere, which are east and west of the Greenwich meridian.