CTR Calculator

Click-through rate is clicks divided by impressions, and this works it three ways. The first takes impressions and clicks, with spend and conversions optional, and returns CTR, cost per click, CPM, conversion rate and cost per conversion. The second turns a target CTR into the number of clicks it needs on the impressions you have. The third compares two versions with a two-proportion z test, so a lift you can see in the numbers is checked against the chance of it being noise before you act on it.