What Is Click-Through Rate (CTR)? Definition, Formula, and What It Hides

Short answer: click-through rate is the number of clicks divided by the number of times something was shown, expressed as a percentage. It measures how well a headline, ad, link, or button earns a click. It says nothing about what happened afterwards, so always read it next to conversion.

Table of Contents

1. The Formula
2. Where CTR Is Used
3. What Counts as an Impression
4. What CTR Hides
5. On-Page CTR
6. Key Takeaways

The Formula

CTR = clicks ÷ impressions × 100

200 clicks from 10,000 impressions is a CTR of 2%.

Where CTR Is Used

Be careful with email. "Click rate" usually divides by emails delivered. "Click-to-open rate" divides by emails opened. They are different numbers, and open tracking itself has become unreliable because mail clients preload images.

What Counts as an Impression

The denominator is where CTR goes wrong.

• Search: an impression is counted when your result is on the page the searcher loaded, whether or not they scrolled to it. A result in position nine gets impressions that few people saw.
• Display ads: served is not the same as viewed. An ad below the fold may never be seen.
• On-page buttons: if you divide clicks by page views, a button at the bottom of a long page looks weak even if everyone who reached it clicked.

For on-page elements, the fairer denominator is the number of sessions that scrolled far enough to see the element (scroll depth).

What CTR Hides

A high CTR is not the goal. The goal is what comes after.

An ad that states the price will filter out people who would not buy. Its CTR falls and its cost per sale often improves. Optimising for CTR alone pushes you towards the first and third rows (vanity metrics).

There is no universal "good" CTR. It varies with position, intent, channel, and brand recognition. Compare each item with its own history and with similar items in the same position, not with an industry figure.

Search CTR is also changing for reasons outside your control. When an AI summary answers the question on the results page, fewer people click any result (zero-click searches).

On-Page CTR

For buttons and links on your own site, clicks are easy to count and easy to misread.

1. Use a click heatmap to see what share of clicks each element receives, by device (click heatmaps).
2. Check how many sessions saw it with a scroll heatmap.
3. Follow the click. Build a funnel from the click to the outcome (funnels).
4. Look for clicks that do nothing. An element that draws clicks and is not a link is a dead click, and a sign visitors expected something there (dead clicks).

To measure a specific button precisely, send an event:

deepsync("track", "hero_cta_clicked", { variant: "start_free" });

Key Takeaways

• CTR is clicks divided by impressions.
• The definition of an impression changes the number a great deal.
• A high CTR can mean a misleading message.
• Read CTR together with what happens after the click.

Conclusion

CTR tells you whether a message earned attention. Whether that attention was worth having is answered further down the funnel.

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