Vocabulary
How the ad auction works
By Oliver Wakefield-Smith, Digital Signet. Updated July 2026.
In the milliseconds after someone hits search, Google runs an auction among every eligible ad. Ad Rank decides who shows and in what order, and it also sets what each click costs. Here is the whole thing with four bidders.
The four steps
- 1A search triggers an auction among every eligible ad for that query
- 2Each ad gets an Ad Rank from bid, quality, thresholds, context and assets
- 3Ads are ordered by Ad Rank; those below the thresholds do not show
- 4Each winner is charged the minimum needed to beat the ad rank below them
Ad Rank's documented components: your bid, the quality of your ad and landing page, the ad rank thresholds, the context of the search, and the expected impact of assets and other ad formats Google Ads Help, 2026 data.
The board, worked
Auction board · simplified teaching model
| Bidder | Max bid | Quality | Ad Rank | Position | Pays per click |
|---|---|---|---|---|---|
| Bidder B | £2.50 | 10 | 25 | 1 | £2.01 |
| Bidder A | £4.00 | 5 | 20 | 2 | £3.61 |
| Bidder C | £3.00 | 6 | 18 | 3 | £2.01 |
| Bidder D | £1.50 | 8 | 12 | 4 | n/a (below the cutoff in this example) |
The model here: Ad Rank = bid x quality. Bidder B ranks first on a £2.50 bid because a 10 quality doubles it to 25. Bidder A bid £4.00, the most money in the auction, and still ranks second.
Each winner pays just enough to beat the ad rank below them: the ad rank underneath divided by their own quality, plus a penny. Bidder B pays 20 / 10 + £0.01 = £2.01, not their £2.50 bid.
Google's real formula also weighs ad rank thresholds, auction context and the expected impact of assets, and prices sit within your bid rather than following this exact arithmetic. The pay-just-enough-to-beat-the-next-ad principle is the documented part. Google Ads Help, 2026 data Google Ads Help, 2026 data
What the board teaches
Money alone does not win. Bidder A brought the biggest bid in the auction, £4.00, and ranks second behind a £2.50 bid with better quality. And the winner's price is set from below: B pays £2.01 because that is what beating A's ad rank requires at B's quality. Improving quality is therefore a price cut you engineer yourself; that mechanism is unpacked on Quality Score and CPC.
The bid-vs-charge distinction is on actual CPC vs max CPC, the arithmetic side on how CPC is calculated, and if your auctions keep pricing high, start at why is my CPC so high.