How to calculate CPC, and the two ways round it
The direct version is spend ÷ clicks: $100 that bought 200 clicks is a $0.50 CPC. The useful versions are the other two. If a publisher quotes you a CPM instead, CPC = CPM ÷ (CTR × 10) — an $18 CPM at a 2.5% click-through rate is $0.72 a click, because $18 buys a thousand impressions and 2.5% of those is 25 clicks. And if you know what a conversion is worth to you, max CPC = target CPA × conversion rate: a $40 target cost per acquisition at a 4% conversion rate means you can pay $1.60 a click and still hit your number. That last one is the bid ceiling, and it is the figure worth knowing before an auction rather than after.
Three ways to arrive at the same number
CPC is what you actually paid per click, but you can also estimate it before you have real data: from CPM and click-through rate (useful for display/video campaigns before launch), or from a target cost-per-acquisition and expected conversion rate (the maximum you can afford to pay per click and still hit your CPA goal). All three methods are available from the Calculate mode — switch the Calculation Method to match what data you have.
Why Planning mode matters
Planning mode reverses the calculation: given your budget and expected conversion rate, it estimates how many clicks and conversions you can afford, plus a break-even CPC — the most you could pay per click and still cover your target revenue per conversion. Use it to set a realistic bid ceiling before a campaign launches.
CPC alone does not tell you if a campaign is working
A low CPC looks good but says nothing about whether those clicks convert into paying customers. Pair CPC with your actual conversion rate and revenue per conversion (or check the ROAS Calculator) to judge real campaign performance, not just click cost.
What this calculator does not cover
This models a single campaign or ad group at a point in time — it does not account for auction dynamics, quality score, bid adjustments, or how CPC shifts over the life of a campaign. For overall ad efficiency across a whole campaign, see the CPM and ROAS Calculators.