The scale factor can be determined by comparing the dimensions of the original rectangle to the scaled copy.
If the side that corresponds to 1 unit in the original rectangle is 5 units in the scaled copy, the scale factor is calculated as follows:
\[ \text{Scale Factor} = \frac{\text{Dimension of Scaled Copy}}{\text{Dimension of Original Rectangle}} = \frac{5}{1} = 5 \]
Therefore, the scale factor is 5.