CTR, or Click-Through Rate, is a metric used in digital advertising that measures the percentage of clicks a link or ad receives relative to the number of times it was viewed or displayed. The formula for calculating CTR is as follows:

CTR = (Total Clicks on Ad) / (Total Impressions)

For example, if an ad was displayed 10,000 times and received 500 clicks, the CTR would be:

CTR = 500 / 10,000 = 0.05 or 5%

This means that for every 100 times the ad was displayed, it received 5 clicks.

CTR is a key metric used to measure the effectiveness of an ad campaign. A higher CTR indicates that the ad is resonating with the target audience and generating more clicks, while a lower CTR may indicate that the ad is not well-targeted or not engaging enough to drive clicks.