The price of a visit, not its value
CPC measures the price of a visit, not what it brings in. A €0.20 click that never converts costs more than a €3 click that converts once in twenty: the second yields a sale for €60, the first none at all.
CPC derives from two quantities: the cost of impressions and the click-through rate. At a €10 CPM and a 1% click-through rate, a thousand impressions produce ten clicks, or €1 per click. When CPC moves, the first question is therefore which of the two has changed: the price of the audience, or interest in the ad.
You also need to know which click you are counting. In its reports, Meta distinguishes all clicks (including reactions and opening the comments or the profile) from link clicks alone, which lead to your site. A CPC calculated on all clicks looks flattering; only cost per link click compares with a search CPC.
How the price of a click is set
On Google Ads, the price of a click is set at auction, on every search. According to Google's documentation, the advertiser pays the minimum needed to clear the Ad Rank thresholds and beat the advertiser just below, often much less than their maximum bid.
The bid is not the only factor: the ad's estimated quality (expected click-through rate, relevance, landing page experience) also goes into the ranking. A more relevant ad can win the same position for less.
Quality Score, rated from 1 to 10 in Google Ads, is its best-known reflection. But according to Google's documentation, it is not an input in the auction: it is a diagnostic tool. Improving it for its own sake makes no sense; it only tells you where to look.
A rising CPC is not always bad news
With automated bidding, CPC is no longer a setting but a consequence. The algorithm bids higher where it judges a conversion likely, and is willing to pay a lot for clicks that stand a chance of converting. A rising CPC with a stable CPA reflects better-chosen traffic, not drift.
The real warning sign is the opposite case: a stable or falling CPC with a rising CPA. The campaign is buying cheaper clicks because it is finding them where they are worth less: low-quality placements, overly broad queries, less interested audiences.
CPC should therefore always be read in pairs: with the conversion rate, to know what a click is worth, and with the click-through rate, to understand why it costs what it does.
Frequently asked questions
How do you calculate CPC?
Divide spend by the number of clicks over the same period. €600 of spend for 400 clicks gives a CPC of €1.50. On Meta, check that the calculation uses link clicks, not all clicks.
What is a good CPC?
A CPC that fits your target cost per acquisition. The maximum CPC you can afford equals your target CPA multiplied by your conversion rate: with a €50 target CPA and a 2% conversion rate, a click can cost up to €1.
Why is my CPC going up?
Either the cost of impressions is rising (competitive pressure, seasonality, a saturated audience) or the click-through rate is falling (a worn-out or less relevant ad). With automated bidding, it can also rise because the algorithm is paying more for clicks that are more likely to convert, which is not a problem as long as CPA holds.
What is the difference between CPC and CPM?
CPM is the price of a thousand impressions, CPC the price of one click. They are linked by the click-through rate: at an €8 CPM and a 2% click-through rate, CPC is €0.40. Neither tells you whether the campaign is profitable; that is the job of CPA.