CPM, CPC and CTR: Connect the Three Advertising Metrics
Connect CPM, CPC and CTR with consistent campaign data. Follow worked examples, avoid percentage errors, and compare click costs before judging results.
CPM measures cost per thousand impressions, CPC measures cost per click, and CTR measures clicks as a share of impressions. For matching data, CPC = CPM ÷ (1,000 × CTR as a decimal). At a $12 CPM and 2% CTR, average CPC is $0.60.
Start with one consistent data set
Choose one campaign, reporting period, currency and click definition before calculating. Mixing link clicks with all clicks, or impressions from a different date range, breaks the relationship between the metrics. Impressions are exposures and do not tell you how many unique people saw an ad.
Google Ads defines CTR as clicks divided by impressions. Its average CPC definition uses actual click costs divided by clicks. The calculations below use the same reported spend for all three measures; a platform may display different cost components in other reports.
| Metric | Formula | What it answers |
|---|---|---|
| CPM | Spend ÷ impressions × 1,000 | What did a thousand exposures cost? |
| Average CPC | Spend ÷ clicks | What did each click cost? |
| CTR | Clicks ÷ impressions × 100% | What share of exposures produced clicks? |
Calculate a campaign from the raw counts
Assume a hypothetical campaign spends $600, delivers 50,000 impressions and receives 1,000 clicks. Its CPM is $600 ÷ 50,000 × 1,000 = $12. Its CPC is $600 ÷ 1,000 = $0.60. Its CTR is 1,000 ÷ 50,000 × 100% = 2%.
You can check the relationship without the raw totals: $12 ÷ (1,000 × 0.02) = $0.60. If you enter CTR as the number 2 instead of 0.02, the equivalent formula is CPC = CPM ÷ (10 × CTR percentage). Confusing those two forms creates a hundredfold error.
Use the CPM calculator, CPC calculator and CTR calculator to cross-check an export. Keep unrounded source data until the final display; rounding small CTRs early can change the reconstructed CPC substantially.
Why a lower CPM may still cost more per click
Lower impression cost does not guarantee lower click cost. Consider two hypothetical placements with consistent measurement. Placement A has $8 CPM and 0.5% CTR, producing $1.60 CPC. Placement B has $12 CPM and 2% CTR, producing $0.60 CPC. B costs more per thousand exposures but less per click.
That comparison still does not establish the better business result. If A's visitors buy more often or purchase products with higher contribution, A could outperform after costs. Carry the analysis through orders, net revenue, variable costs and ad spend before choosing where to allocate the next dollar.
Handle zero clicks and aggregate results correctly
With positive impressions and zero clicks, CTR is zero and CPM can still be calculated. CPC is undefined because there are no clicks to divide the spend by. Report that condition directly instead of entering zero CPC, which would incorrectly imply free traffic.
For a combined report, add spend, impressions and clicks first, then calculate the ratios. Do not take an unweighted average of campaign CPCs or CTRs. A campaign with ten clicks should not receive the same weight as one with a thousand clicks when computing overall CPC.
Turn the metrics into a planning scenario
At $0.60 CPC, a hypothetical 2% click-to-order conversion rate implies $30 ad spend per order: $0.60 ÷ 0.02. This assumes conversion remains constant and does not predict auction behavior. Compare that $30 with contribution per order before advertising.
Record the scenario in the campaign profitability workbook, available from resources. Keep the measured campaign and the planning assumptions labeled separately so a forecast cannot be mistaken for an observed result.