What Is an Impression? Impressions, Reach, Frequency and CPM in Ads

An impression is one showing of your ad: each time the ad is displayed on a screen or a page, the platform counts one impression. Impressions tell you how often an ad was shown, not how many different people saw it and not whether anyone paid attention, so the number only makes sense when you read it next to reach, frequency and clicks.

The exact counting rule is set by each ad platform. Meta, Google Ads and TikTok each publish their own definition in their help centres, and the small differences between them explain a lot of the confusion when a report from one platform is compared with another. This guide covers those definitions, the metrics that are built on top of impressions (reach, frequency, CPM, CTR and viewable impressions), and how to decide which of them to optimise for.

How Meta, Google Ads and TikTok each count an impression

All three platforms use the word "impression", but the rule behind the count is not identical. Before you compare numbers across platforms, it helps to know what each one is actually counting.

Meta (Facebook and Instagram)

Meta's Business Help Center defines impressions as the number of times your ads were on screen. The counting rule is specific: an impression is counted the first time an instance of an ad is on screen. If someone scrolls past an ad and then scrolls back up to the same ad, that is still one impression. If the same ad is on screen for the same person at two different times in a day, that is two impressions.

Meta counts images and video the same way, with the exception of ads on Meta Audience Network. That means a video ad does not have to start playing for the impression to count, and Meta notes that this differs from industry standards for video ads. In a few cases where Meta cannot tell whether an ad was on screen, such as on feature phones, the impression is counted when the ad is delivered to the device. Impressions from invalid traffic that Meta detects, such as bots, are not counted.

Google Ads

Google Ads Help defines it this way: an impression is counted each time your ad is shown on a search result page or another site on the Google Network. Partial showings also count. If only part of an ad appears, for example only the business name and location on Google Maps, Google still counts one impression. In the reporting columns the metric is often shortened to "Impr."

On the Search Network this means an impression is recorded when your ad appears on the results page for a query, whether or not the searcher scrolled down far enough to notice it. On Display and Video, Google adds a separate layer of measurement called Active View, covered in the viewable impressions section below.

TikTok

TikTok Ads Manager's basic metrics article defines impressions as the number of times ads were shown. The same article defines reach as the number of unique users who saw ads at least once, and frequency as the average number of times each user saw an ad over a given time period. That basic article does not spell out a scrolling or time-on-screen rule, so do not assume TikTok's count follows Meta's "first time on screen" logic exactly. When you need the precise rule for a specific placement, check TikTok's own help pages for that placement.

Why the three numbers cannot simply be added up

Because each platform applies its own rule, 100,000 impressions on Meta, 100,000 on Google Display and 100,000 on TikTok are three different measurements that share a name. They are fine for tracking each platform against itself over time. They are a weak basis for a single "total views" figure in a cross-channel report.

Impression vs reach vs frequency

These three metrics describe the same delivery from different angles. Impressions count showings. Reach counts people (or accounts). Frequency tells you how many times, on average, each of those people saw the ad.

Meta defines reach as the number of Meta accounts that saw your ads at least once, and points out that reach differs from impressions because impressions may include several views by the same account. Meta also states that reach is an estimated metric calculated from sampled data. Meta calculates frequency as impressions divided by reach.

A worked example, with illustrative numbers only: an ad set records 30,000 impressions and a reach of 12,000 accounts over seven days. Frequency is 30,000 / 12,000 = 2.5, so the average person in that audience saw the ad two and a half times during the week.

One practical consequence: reach is deduplicated within the period you are looking at. If you add up the reach for each of the seven days, you will get a bigger number than the seven-day reach, because the same person who saw the ad on Monday and Thursday is counted once in the weekly figure but once on each day in the daily figures. Impressions, on the other hand, do add up across days.

What viewable impressions are

A viewable impression is an impression where the ad had a real chance of being seen. Google Ads measures this with Active View on Display and Video campaigns, and its help page says the Active View metrics follow the Media Rating Council (MRC) standards:

• A display ad is viewable when at least 50% of its area is visible on screen for at least one second.
• For large display ads of 242,500 pixels or more, the threshold is at least 30% of the area visible for at least one second.
• A video ad is viewable when at least 50% of its area is visible on screen while the video plays for at least two seconds.

This is a stricter test than the plain impression count. An ad served at the bottom of a long page that the visitor never scrolls to can still register an impression but will not register as viewable. On Meta, impressions from certain placements are accredited by the MRC, and the impression is counted when the ad is on screen, but as noted above a Meta video impression does not require the video to play.

If you run Google Display or Video campaigns, add the Active View columns to your reports. The gap between impressions and viewable impressions tells you how much of the delivery happened where people were unlikely to see it.

What CPM is and how to calculate it

CPM stands for cost per mille, or cost per 1,000 impressions. Meta describes it as the average cost for 1,000 impressions and gives the formula: amount spent divided by impressions, multiplied by 1,000.

Illustrative example: a campaign spends 6,000 baht and receives 400,000 impressions. CPM = 6,000 / 400,000 x 1,000 = 15 baht. Every thousand showings cost 15 baht on average.

CPM is used in two different ways, and it is easy to mix them up:

• As a reporting metric. Every campaign has a CPM in its report, even one that is charged per click, because you can always divide spend by impressions.
• As a bidding or pricing model. Google Ads' glossary describes CPM as a way to bid where you pay per one thousand impressions on the Google Display Network, and adds that viewable CPM (vCPM) bidding means you only pay when your ads can be seen.

A low CPM is not automatically good. Cheap impressions can come from placements where attention is low, so always look at CPM together with viewability, click-through rate and cost per result.

When high impressions with low clicks is a problem

Click-through rate (CTR) is clicks divided by impressions. Lots of impressions with few clicks gives a low CTR, but whether that is a problem depends on what the campaign is meant to do.

For an awareness campaign whose job is to put a brand in front of as many relevant people as possible, clicks were never the goal, and a low CTR may be acceptable as long as reach and frequency are on plan. For a traffic, lead or sales campaign, a low CTR means you are paying for exposure that is not turning into action, and it is worth investigating.

Places to check when impressions are high and clicks are low:

1. Search terms (Google Ads Search). Open the search terms report and look for queries that do not match what you sell. Broad keyword coverage can trigger your ad on searches where the searcher had no intent to click. Add negative keywords for the irrelevant ones.
2. Placements (Display, Audience Network, in-app). Break the report down by placement. A small number of apps or sites can take a large share of impressions with very few clicks.
3. Audience breadth. A very broad audience produces many impressions among people who were never likely to be interested. Narrowing it can lowers impressions and raises CTR.
4. Creative and offer. If the first second of a video or the headline does not say what is on offer, people scroll past. Test a version that states the offer and the action straight away.
5. Frequency. If the same people have already seen the ad many times, extra impressions add little. See the next section.

How frequency causes ad fatigue

Frequency is useful up to a point. Seeing a message more than once helps people remember it, and Meta's frequency page notes that frequency helps build awareness and recall. The same page warns that if performance begins to drop as frequency rises, your audience may be experiencing ad fatigue, and suggests changing the ad creative or the targeting.

There is no universal "safe" frequency number. What matters is the trend in your own data. The pattern to watch for is frequency climbing while CTR falls and cost per result rises over the same date range. When you see those three lines move together, the audience has probably seen the ad enough.

Ways to manage it:

• Rotate creative. Have new versions ready before the current ones wear out, so a refresh does not depend on a crisis.
• Widen or change the audience. Since frequency is impressions divided by reach, reaching more people with the same budget lowers frequency.
• Use frequency caps where the platform offers them. In Google Ads, frequency capping limits how many times your Display or Video ads appear to the same person. For Display campaigns you set the number of impressions allowed per user per day, week or month, at the campaign, ad group or ad level. For Video campaigns you can cap impressions and/or views per day, week, month or a combination, at campaign level.

Which metric to optimise for: awareness vs conversion

Impressions are an input. They tell you the ad was delivered. The metric you optimise for should match the business goal of the campaign.

• Awareness. Focus on reach, frequency, CPM and, where available, viewable impressions. The question is how many of the right people saw the message, how often, and at what cost per thousand.
• Consideration and traffic. Focus on CTR, cost per click and what happens after the click, such as landing page views and time on site.
• Conversion. Focus on conversions, cost per result and return on ad spend. Impressions and CPM still matter for diagnosis, but a campaign with a high CPM can be the most profitable one if the people it reaches convert.

Choose the campaign objective that matches the goal, because each platform's delivery system works towards the objective you select. Asking a conversion campaign to also deliver the lowest possible CPM usually means neither goal is met well.

What this means for campaigns in Thailand

The definitions are the same in Thailand as anywhere else, but a few local situations change how the numbers behave:

• CPM is reported in your account currency. If the ad account is set to Thai baht, CPM and spend are shown in baht. A CPM figure quoted in US dollars from another market comes from a different auction and cannot be compared directly.
• Tight geographic targeting raises frequency fast. A campaign aimed at one province or a small radius around a branch in Bangkok has a limited pool of people. With the same budget, impressions keep rising while reach stops growing, so frequency climbs. Watch frequency closely on local campaigns and refresh creative more often.
• Thai and English versions of the same ad. When both language versions run to an overlapping audience, the same person can see both. Each version reports its own impressions, so look at reach and frequency at the ad set or campaign level, not only per ad.
• Cross-platform reports. When a campaign runs on Meta, Google and TikTok at once, report impressions per platform, and use reach, clicks and conversions for the combined view rather than one summed impression total.

Frequently asked questions

Is an impression the same as a view?

No, an impression is one showing of an ad, while a "view" usually has a stricter meaning such as a video watched for a set time or a viewable impression under the MRC standard. On Meta, a video impression does not require the video to play at all, which is why impressions on video ads are normally higher than video views.

Does an impression mean someone actually saw my ad?

Not necessarily, because an impression only confirms that the ad was shown or on screen under the platform's rule. Viewable impression metrics such as Google's Active View, plus engagement metrics like clicks, are closer measures of whether people actually noticed it.

Do I pay for every impression?

It depends on how the campaign is bid and charged: with CPM bidding you pay per thousand impressions, and with Google's vCPM you pay per thousand viewable impressions. With click-based bidding you pay when someone clicks, even though impressions are still counted and CPM still appears in the report.

What is a good number of impressions?

There is no universal good number, because impressions depend on your budget, the size of your audience and the CPM in your auction. A more useful question is whether the campaign reached the people it was meant to reach at a frequency that did not cause fatigue.

Why does my reach not add up across days or ad sets?

Reach counts unique people within the period and grouping you select, so the same person is counted once in a weekly total but once per day in daily figures. Meta also notes that reach is estimated from sampled data, so small differences between views are normal.

Getting impressions to work for your goals

Impressions are where every ad report starts, but the decisions come from reach, frequency, CPM and what happens after the click. If you want help setting up campaigns that are measured against the right metric for each goal, Relevant Audience manages Facebook and Instagram ads, Google Ads campaigns, TikTok ads and display advertising for businesses in Thailand.