Whenever someone searches on Google, an ad auction kicks off behind the scenes to determine which ads (if any) will appear alongside the organic search results. Advertisers bid on specific keywords and phrases they reckon their target audience will use when searching for relevant products or services.
For example, if you run a sportswear shop specialising in running gear, you might bid on keywords like "best running trainers," "buy running shoes online UK," or even more specific terms like "Nike Air Zoom Pegasus 38 running trainers." The aim is to bid on phrases that potential customers are likely to search for when looking for what you're selling.
One thing that surprises most business owners when I walk them through this: winning the auction doesn't mean paying the most. I regularly show clients that a competitor outranking them is paying less per click, not more, because their account is better structured. Most people assume Google Ads is basically a bidding war. It isn't.
How ads get ranked
When an ad auction is triggered, Google ranks all the eligible ads based on a calculation called "Ad Rank." An ad's position in the rankings depends on several factors:
Bid Amount: This is the maximum an advertiser is willing to pay for a single click on their ad. The higher the bid, the higher the ad will probably rank.
Ad Quality: Google also considers the overall quality and relevance of the ad when calculating Ad Rank. This includes:
Expected Click-Through Rate (CTR): An estimate of how likely users are to click your ad based on past data.
Ad Relevance: How well the ad copy matches and relates to the user's search query.
Landing Page Experience: The relevance, usability, and load speed of the webpage the ad sends users to.
Ad Extensions and Formats: Things like displaying a phone number or site links, and ad formats like product listing ads, can also impact an ad's position.
Why Quality Score matters
One of the biggest factors in Google's ad auctions is Quality Score. This is Google's rating (from 1 to 10) of the overall quality and relevance of your ads, keywords, and landing pages.
Quality Score is based on the ad quality components above: expected CTR, ad relevance, and landing page experience. The higher your Quality Score, the less you'll need to bid to earn higher ad positions and keep costs down. A low Quality Score means you'll have to bid way more to rank well.
For example, let's say your ad has a Quality Score of 5/10 and a competitor's is 8/10. Even if you bid higher, their ad will likely rank above yours thanks to its better quality. That's why continually optimising Quality Score matters.
Meeting Google's ad ranking requirements
To be eligible for having ads displayed, your campaigns must clear certain Ad Rank thresholds set by Google. These are based on the calculated Ad Rank from your bid, Quality Score, and other factors combined.
Essentially, Google wants to ensure only highly relevant, quality ads from legit advertisers are shown for each search. Even if you bid the most, your ads won't be allowed to show unless they meet the minimum Ad Rank criteria.
How cost-per-click is actually calculated
You might assume that if you bid, say, £1.50 per click, that's what you'll get charged whenever someone clicks your ad. But the actual amount you pay for each click (your "actual CPC") is typically lower than your maximum bid.
This is because Google aims to keep ad auctions competitive by encouraging multiple advertisers to bid on keywords. Instead of charging you your full max bid, your actual CPC is worked out using this formula:
Actual CPC = (The Ad Rank of the ad below you / Your Quality Score) + £0.01
This ensures you only pay the bare minimum required to outrank and appear above the ad below you in the rankings, not a penny more.
For example, let's say your Quality Score is 6 and the Ad Rank of the advertiser below is 4.5. Plugging into the formula:
Actual CPC = 4.5 / 6 + £0.01 = £0.76
So even if your max bid was £2 per click, you'd only pay 76p based on that auction result.
The outcome of an ad auction
After all the calculations, an ad auction determines three main things:
Which ads meet the minimum Ad Rank thresholds and will be displayed on the search results page.
The specific order and position those eligible ads will appear in based on their Ad Rank.
The actual cost-per-click each advertiser will pay if someone clicks their ad during that auction.
A simple illustrated example
To illustrate how it all works, let's walk through an example auction:
Let's say three advertisers are competing to show ads for the search "best men's running trainers UK":
Advertiser A: Bids £2 per click, has a Quality Score of 8/10
Advertiser B: Bids £3 per click, has a Quality Score of 5/10
Advertiser C: Bids £1.50 per click, has a Quality Score of 7/10
The Ad Rank would be calculated as:
Advertiser A: £2 x 8 = 16
Advertiser B: £3 x 5 = 15
Advertiser C: £1.50 x 7 = 10.5
Based on these Ad Ranks, Advertiser A would show in the number 1 ad position because their higher Quality Score gave them the edge over Advertiser B's higher bid amount.
Advertiser B would appear in position number 2, while Advertiser C wouldn't meet the Ad Rank threshold to show an ad for this search.
As for costs, if Advertiser A's actual CPC is £1, then Advertiser B would pay: Actual CPC = 16/5 + £0.01 = £3.21
So despite bidding £3 per click, Advertiser B ends up paying just over £3.20. Meanwhile, Advertiser A pays only £1 despite bidding £2 - thanks to the competitive auction dynamics.
Why this matters for your business
I had a client in North Wales, a local service business, who was convinced that the reason a national competitor was outranking them was that the competitor was simply bidding far more than they could afford to match. They'd been gradually pushing up their maximum bids to compete, watching their CPA climb with each increase, and getting nowhere. When I audited the account, their keywords were sitting at Quality Scores of 4 and 5. The competitor wasn't paying more per click. They were paying less, because their Quality Scores were significantly higher. Once we tightened the ad group structure, rewrote the ad copy to match the search intent more precisely, and improved the landing page relevance, Quality Scores moved to 7 and 8 over the following month. CPCs dropped. Their position improved. They'd been trying to solve a Quality Score problem with a bidding solution, and it had been making things worse.
Bid amounts alone don't guarantee desirable ad positioning. An advertiser with a higher Quality Score can consistently outrank competitors who are bidding more, and pay less per click for the privilege. This has direct practical implications for how you should approach campaign management.
Quality Score deserves more attention than most advertisers give it. A higher Quality Score means you pay less per click and earn better positions simultaneously. The improvement in CPC from tightening ad groups and improving landing page relevance is often larger and more durable than any bid adjustment could produce.
In practice, a keyword with a Quality Score of 4 might cost £4.00 per click to maintain position 2. The same keyword with a Quality Score of 8, achieved by tightening the ad group to match the keyword's intent more precisely and improving the landing page, might cost £2.00 per click for the same position. That's a 50% reduction in CPC without touching bids, achieved entirely through relevance improvements.
The account-level implication is significant. Every keyword in your account has a Quality Score. Accounts with consistently high Quality Scores across their keyword portfolios pay structurally less than competitors with poor Quality Scores, not just on a keyword-by-keyword basis, but as a compounding advantage across every auction. When I audit accounts, the relationship between Quality Score and CPC efficiency is one of the clearest patterns: well-structured accounts with relevant ads and landing pages consistently outperform higher-spending accounts with poor structure.
Ad Rank thresholds also protect the searcher experience. Even with an unlimited budget, you can't buy your way to position 1 if your Quality Score and ad relevance are poor. Google will simply not show your ad at all rather than show a poor-quality ad, regardless of what you're willing to pay. This is why conversion tracking and account structure matter so much: they determine whether your account is competitive in auction, not just whether you've allocated enough budget. The 20 most common ways Google Ads performance gets quietly undermined covers the structural mistakes, many of them rooted in misunderstanding exactly this dynamic, that result in accounts paying structurally higher CPCs than they should be.
For a full breakdown of how to improve Quality Score through landing page relevance, read Improving Your Google Ads Quality Score with Landing Page Keywords.
Google Ads management in North Wales. If you'd like to see how your account's Quality Scores compare and where CPC improvements are achievable, get in touch for a free audit.
