Impressions in marketing and advertising

What is an impression in marketing and advertising? How to calculate how many impressions you will serve

Impressions calculator

What is an impression in marketing

An impression in digital marketing and advertising is a count of every time your ad (paid or organic) is served to a user. The term impression is relevant for all types of digital marketing and advertising - from Facebook video ads to Google's cost per click text ads - it is simply the collective word used to say "the number of ads served”.

In a typical digital media campaign, the marketer will have an impression goal to work towards in order to deem it "delivered in full". This is why it is important to track how many impressions you have served during a campaign, ensuring that as an advertiser you are getting what you pay for.

Impressions formula

To calculate impressions, you need the following metrics:

  1. Ad spend / budget / revenue
  2. CPM (cost per thousand)


How is an impression requested, counted and displayed

When you browse a website or app that features advertising space or ad tags, the code will make a call to the publisher’s ad server asking which ad to serve to the user. The website will then display the selected ad to the user. This is how impressions are served in their simplest form.

An ad server will typically register and count an impression when the creative is downloaded on the user’s device and has started to load on the webpage; however, this may not be the case for all ad servers. If you are looking for an ad server to use, make sure they are using a strict methodology to ensure it only counts ads once the creative is rendered.

If there are multiple ad formats served at the same time to the user on one page, each formats’ impression count will increase by 1.

Impressions vs clicks - what should you optimise to?

This depends on your campaign goals and objectives. In branding campaigns when you do not need to direct a user to a landing page and the goal is to watch a video or view a banner ad, you should optimize towards a brand metric such as impression delivery, reach or VTR (view-through rate) with video. In branding campaigns, the fact that you reached your target delivery goal of users reached or impressions served is enough for it to be deemed a success.

For performance or direct response campaigns, when you have a goal of pushing users to a landing page or driving a sale, you should optimize towards clicks or a conversion event; in this case, it does not matter how many impressions you served if the budget is being spent efficiently.

Impressions delivery issues

There are a number of reasons why your impressions might not be delivering at the rate you were expecting.

In fixed CPM campaigns, the issue may revolve around a publisher overselling impressions, meaning there are not enough ad slots available for your brand to take within the campaign period. On the other side, it could be that the publisher site is experiencing a loss of traffic or a server outage that means fewer users could access the site at that time.

In variable CPM campaigns (eCPM), the reason may be a higher delivered CPM than expected, meaning while you are still spending the budget at an even pace, the impressions you are serving for the same budget are fewer than planned.

In both methods of buying impressions, you should always use a pacing tracker to ensure both budget and impressions are on track.

Related metrics