Vocabulary
How is CPC calculated?
By Oliver Wakefield-Smith, Digital Signet. Updated July 2026.
Two calculations share one name. Your average CPC is simple division you can do from an invoice. The actual CPC charged per click is set by an auction you never see. This page does both, with the same worked week.
Average CPC = spend / clicks · Actual CPC = set per auction
The first is your bookkeeping. The second is the platform's pricing. Google Ads Help, definition Google Ads Help, actual CPC
Calculation 1: your average, from a real week
One campaign, one week
£2.40 average. No single click necessarily cost £2.40; some cost £1.80, some £3.10. The average is what planning runs on, and it is the number the find-your-CPC calculator computes.
Calculation 2: what each of those clicks actually cost
Each click was priced by an auction. Google ranks ads by Ad Rank (bid, quality, context and more), and charges each winner the minimum needed to clear the thresholds and beat the ad rank below them Google Ads Help, 2026 data Google Ads Help, 2026 data. In the simplified board below, the top bidder pays £2.01 against a £2.50 bid:
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 full walkthrough of this board is on the ad auction page.
Why your average differs from your bid
Your max CPC bid is a ceiling, not a price. Most auctions charge less than the ceiling, so a £3.00 bid can produce a £2.40 average. Occasionally conversion-focused automated bidding can spend above a stated per-click figure while holding an average target. The bid-vs-charge gap is unpacked on actual CPC vs max CPC, and the plain formula lives on the formula page.