How Does Google Ads Work? The Auction Explained

Understanding how Google Ads works under the hood helps you run better campaigns and spend your budget more efficiently. Most South African business owners know Google Ads exists but are unclear on the mechanics that determine when ads show, how positions are determined, and what drives costs. This guide explains the full picture. Also see: Google Ads vs SEO.

The Google Ads Auction Explained

Every time someone searches on Google, an automated auction runs in milliseconds to determine which ads appear and in what order. This auction happens behind the scenes, invisible to the searcher. It considers every active ad that is eligible to show for that search and determines placement based on a metric called Ad Rank.

Ad Rank is calculated from two primary inputs: your maximum bid (the most you are willing to pay per click) and your Quality Score (a measure of your ad’s relevance and expected performance). A higher Ad Rank secures a better position. Crucially, a higher Quality Score can allow you to achieve better positions than competitors who bid more but have less relevant ads.

What Happens When Someone Searches on Google?

1. A user types a search query into Google
2. Google identifies all ads with keywords matching that query
3. Each eligible ad enters the auction with its current bid and Quality Score
4. Google calculates Ad Rank for each competing ad
5. Ads with sufficient Ad Rank are shown in position order
6. The searcher sees the results page – organic results plus paid ads
7. If the searcher clicks an ad, the advertiser is charged for that click

How Does Google Decide What to Charge Per Click?

Contrary to what many people assume, you do not pay your maximum bid for each click. Google uses a system called the Vickrey auction (second-price auction), where you pay just enough to beat the Ad Rank of the competitor below you – often significantly less than your maximum bid. This means the actual cost per click in your Google Ads account is typically lower than the maximum you set.

The actual CPC formula is: (Ad Rank of competitor below you / your Quality Score) + R0.01. In practice, this means improving your Quality Score directly reduces your actual cost per click, even without changing your bid. This is why Quality Score optimisation is such a high-priority activity for budget-conscious South African advertisers.

What is Quality Score and Why Does It Matter?

Quality Score is Google’s rating of the quality and relevance of your keywords, ads, and landing pages. It is scored from 1 to 10 and is composed of three components:

• Expected Click-Through Rate (CTR): How likely is someone to click your ad when shown for this keyword?
• Ad Relevance: How closely does your ad match the intent behind the keyword?
• Landing Page Experience: How useful, relevant, and fast is the page users land on after clicking?

A Quality Score of 7-10 is considered good. A score of 1-3 indicates your ad is poorly matched to the keyword and landing page, which results in higher costs and lower positions. Improving Quality Score through better ad copy and landing pages is the most cost-efficient way to improve Google Ads performance.

How Does Google Decide Which Ads to Show?

Google only shows ads that are relevant to the search query, meet quality thresholds, comply with advertising policies, and have sufficient budget. Ads can be disapproved for policy violations (misleading claims, prohibited products, destination issues), and campaigns with exhausted daily budgets stop showing ads for the remainder of that day. Keywords with very low Quality Scores may be marked ‘Below first page bid’ – meaning no amount of budget increase will produce consistent impressions without first improving relevance.

The Full Google Ads Flow for South African Advertisers

1. You create a campaign, choose keywords, set bids, write ads, and set a daily budget
2. When South African users search for your keywords, your ad enters the auction
3. Google calculates your Ad Rank against all competing ads
4. Your ad appears if your Ad Rank is competitive enough
5. A searcher clicks your ad — you are charged the actual CPC (not your max bid)
6. The searcher arrives on your landing page — your conversion rate determines the outcome
7. You review performance data and optimise bids, keywords, and ads based on results

Frequently Asked Questions

Does Google Ads guarantee top position if I have the highest bid?

No. The highest bid does not guarantee top position. Ad Rank combines bid and Quality Score, so a competitor with a lower bid but significantly higher Quality Score can outrank you. This is by design – Google wants to show the most relevant ads, not just the most expensive ones.

How many ads compete in a typical Google auction?

It varies by keyword. Highly competitive commercial keywords like ‘SEO agency South Africa’ or ‘car insurance quote’ may have dozens of advertisers competing. Niche local keywords may have only two or three. The number of competitors directly affects CPC – more competition typically means higher costs.

Can I see which position my ads appear in?

Yes – your Google Ads account shows average position data, impression share, and top-of-page rate metrics. These tell you not just where your ads appeared on average, but how often they appeared at the top of the page versus further down.

Why do my ads not show when I search for my own keywords?

Google personalises search results, so searching from your own device frequently results in your ads not showing (or being shown less often) to avoid skewing your data. Use the Ad Preview and Diagnosis tool in your Google Ads account to check ad visibility without affecting your campaign data.

How does Google Ads work for mobile searches?

The same auction mechanism applies on mobile devices. However, mobile and desktop traffic can behave very differently – mobile searches are often more local and immediate in intent. South African advertisers typically see higher CPC on desktop but higher call rates from mobile searches.