How many rectangles are there in a standard chessboard?

A standard chessboard consists of an $8\times 8$ grid of squares, which means it has $9$ horizontal lines and $9$ vertical lines.
To form any rectangle, we need to choose $2$ horizontal lines out of $9$ and $2$ vertical lines out of $9$.

The number of ways to choose $2$ horizontal lines is given by:

$${}^9{C}_2=\frac{9\times 8}{2\times 1}=36$$

Similarly, the number of ways to choose $2$ vertical lines is given by:

$${}^9{C}_2=\frac{9\times 8}{2\times 1}=36$$

Therefore, the total number of rectangles is:

$$\text{Total Rectangles}=36\times 36=1296$$