CTR formula and clickthrough rate definition

Clickthrough rate definition

Clickthrough rate (CTR) is the number of clicks divided by the number of impressions, written as a percentage. Google Ads’ definition is the clicks an ad receives divided by the times it is shown;^[1] Microsoft Advertising describes CTR as the number of times an ad was clicked divided by its impressions.^[2]

A CTR answers one question: of the people who had the chance to click, how many did? It says nothing about what happened after the click; that is the job of the conversion rate. Marketing courses treat CTR as an engagement measure that sits between reach (impressions) and outcomes (conversions, revenue).^[7]

Worked CTR examples

The same formula works for any channel, but the denominator must be the number of chances to click. For email that is usually delivered (or opened) messages; for search results it is the number of times your result appeared. Google Search Console defines its CTR as click count divided by impression count.^[6] The CTR report page explains how to read those reports.

Which clicks count: link CTR vs CTR (all)

CTR depends on which clicks are in the numerator, and Meta reports two versions side by side. CTR (link click-through rate) is link clicks ÷ impressions;^[3] CTR (all) is clicks (all) ÷ impressions,^[4] where clicks (all) covers clicks, taps or swipes on the ad of any kind.^[5] If you compare a Meta CTR (all) with a Google Ads CTR, you are comparing different things.

CTR formula in Excel or Google Sheets

With clicks in column B and impressions in column C, enter =B2/C2 and format the cell as a percentage, or =ROUND(B2/C2*100,2) for a plain number. Wrap it as =IF(C2=0,"",B2/C2) so rows with no impressions stay blank instead of showing an error. To get a campaign total, divide the sum of clicks by the sum of impressions: =SUM(B2:B20)/SUM(C2:C20).

Why you should not average CTRs

A simple average of CTRs gives every ad the same weight regardless of how often it ran, so it is almost always wrong. Ad A has 1,000 clicks on 100,000 impressions (1%); ad B has 10 clicks on 100 impressions (10%). The average of the two rates is 5.5%, but together they earned 1,010 clicks on 100,100 impressions: 1.01%. Always total first, then divide. The same rule applies to CPC, CPM and conversion rate.

CTR, CPM and CPC are one equation

Because all three share impressions, clicks and cost, any two give the third:

That is why a creative change that lifts CTR also lowers cost per click at the same CPM. Run your own numbers in the CTR calculator or the CPC calculator.

Common errors with the CTR formula

1. Forgetting × 100. 0.024 and 2.4% are the same CTR; 0.024% is a hundred times smaller.
2. Unique clicks over total impressions. Mixing a unique (per-person) numerator with a total denominator understates the rate. Use totals with totals.
3. Including bot or invalid clicks. Platforms filter invalid clicks from billing; raw server logs may not. Use the platform report for paid CTR.

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