The formula to calculate the Open Rate (OR) is:
\[ \text{OR} = \frac{\text{O}}{\text{I}} \times 100 \]
Where:
Let's say the number of opens (O) is 500 and the number of impressions (I) is 2000. Using the formula:
\[ \text{OR} = \frac{500}{2000} \times 100 = 25\% \]
So, the open rate is 25%.