Click-through rate = (Clicks / Impressions) × 100. If 1,000 people see your ad and 30 click it, your CTR is 3%. Simple, but context determines whether that's good or terrible.
For Google Ads: Average search ad CTR is 3-6%. Top performers hit 10%+. Display ads average 0.5-1%. A CTR below average means your ad copy or targeting needs work.
For email: Average email CTR is 2-5%. Triggered emails (welcome, abandoned cart) often hit 10%+. Newsletters average 1-3%.
Why CTR is misleading for landing pages
A high-CTR ad that sends visitors to a page they immediately bounce from is worse than a lower-CTR ad that sends qualified traffic. CTR measures interest, not intent. Clickbait headlines have incredible CTR and terrible conversion rates.
For landing pages, conversion rate is almost always the better metric. A CTA with 15% CTR that leads to a form with 10% completion gives you 1.5% end-to-end conversion. A CTA with 8% CTR leading to a form with 30% completion gives you 2.4% — better outcome despite lower CTR.