Click through rate, frequently abbreviated as “CTR”, is a metric usually used to describe the ability of an ad to generate clicks. CTR is calculated by dividing the number of clicks by the number of impressions. An ad shown 1000 times with 10 clicks would have a 1% click through rate. Click through rate can also be used to describe more general situations where you’re trying to measure the ratio of people who take a certain action when presented with a certain scenario.