Definition: Ad Impression

What is an Ad Impression?

An ad impression is one successful ad call – one ad loading on a webpage is one ad impression. This is what is meant most of the time when the word impression is used (including when calculating CPMs), however it is important to differentiate from a page impression, which refers to when the webpage itself loads.

Although it is simple enough once you get it, everyone struggles to keep this concept straight to begin with. To illustrate – if there are three ads on one webpage when the whole page loads successfully then that would count as one page impression but three ad impressions.

Therefore if you have a website with three ads on every page, and a site that has 10,000 page views per month, you could have up to 30,000 Ad Impressions per month.

Note that you could have up to 30,000, as not every ad will load every time a webpage loads. This could be for many reasons, including:

  • Users closing or moving away from a page too fast for all the ads to load
  • Ad blockers
  • Broken Ad Calls (as in no ad is shown for some reason)

It may sound like these are rare occurrences, but in fact, it is likely up to 30% of potential Ad Impressions will be lost this way.

On top of that, it is often likely your fill rate will not be 100% either, so you cannot bank on selling every ad impression you generate.


What it looks like

What it looks like: Page Impression vs Ad Impressions

Click to enlarge


Other names for Ad Impression (synonyms)

Impression (usually, but not always – it’s what meant most of the time), Ad call (sort of – a successful ad call = an ad impression)


It’s the opposite of (antonyms)

Broken Ad Call (sort of)


Not to be confused with

Page Impression, Viewable Impression


Find out more

Glossary Index