CTR calculation:
clicks ÷ impressions × 100

CTR calculation: the formula

To calculate CTR, divide the number of clicks by the number of impressions and multiply by 100. For 420 clicks on 28,000 impressions the result is 1.5 percent, meaning about 1.5 people clicked for every 100 who saw the ad.

How to calculate CTR in four steps

1. 1Pick one ad, one date range and one placement.
2. 2Read the clicks and impressions for that same period.
3. 3Divide clicks by impressions.
4. 4Multiply by 100 and read the result as a percentage.

A quick check is to move the decimal point. A CTR of 1.5 percent means 15 clicks per 1,000 impressions. If you see 150 clicks per 1,000, the CTR would be 15 percent, which is unusual and worth checking for a counting error.

You can also work backwards to plan. Clicks equal impressions multiplied by CTR, so 20,000 impressions at a 1.5 percent CTR should bring about 300 clicks. A second worked case: a banner shown 50,000 times with 275 clicks has a CTR of 0.55 percent, since 275 ÷ 50,000 × 100 = 0.55.

Combining several ads without the averaging trap

When a campaign has more than one ad, do not average the individual CTRs. Add all the clicks, add all the impressions, then divide once. Averaging treats a tiny ad the same as a huge one.

The simple average overstates performance here because the better ad had fewer impressions. The combined figure of 2.18 percent is the honest one.

Where a CTR calculation is useful

• Comparing two versions of a search ad headline shown the same number of times.
• Checking whether a banner is getting noticed before changing the landing page.
• Spotting a drop after a design change by comparing week against week.
• Reporting email or social posts, where impressions may be replaced by delivered emails or reach.

Make sure the denominator matches the channel. Many email reports divide clicks by emails delivered rather than by opens, so two reports can use the same word CTR and measure different things.

Common mistakes when working out CTR

• Forgetting to multiply by 100 and reporting 0.015 as 0.015 percent.
• Using impressions from one date range and clicks from another.
• Comparing CTRs from different placements, such as search and display, as if they were the same.
• Judging an ad on very few impressions. A CTR from 200 impressions can swing wildly.

CTR is only the first step

CTR tells you how many people were interested enough to click. It says nothing about what happened next, so read it together with cost per click and your conversion rate before deciding an ad is a winner.

For example, an ad with a CTR of 3 percent that brings 300 visitors, of whom 6 buy, is converting 2 percent of visitors. A second ad with a CTR of 1.5 percent that brings 150 visitors, of whom 6 buy, is converting 4 percent. The second ad has the weaker CTR but the better landing-page result.