EPC, CPA and ROI answer different questions. They should not be compared as if they were interchangeable measures of campaign performance.
EPC: earnings per click
EPC estimates the commission generated per measured click.
Formula: EPC = attributed commission ÷ eligible clicks.
For example, if a publisher receives ₹12,000 in approved commission from 4,000 eligible clicks, EPC is ₹3.00. If the denominator includes invalid clicks, repeated clicks or a different date window, the result changes. State the click definition and commission status used.
CPA: cost per acquisition or action
CPA measures the cost associated with acquiring a defined outcome.
Formula: CPA = campaign cost ÷ approved acquisitions.
If an advertiser spends ₹30,000 and receives 150 approved acquisitions, CPA is ₹200. Do not use submitted leads in the denominator if the business objective is approved customers.
ROI: return on investment
ROI compares net gain with investment.
Formula: ROI = (net gain − investment) ÷ investment × 100%.
For performance campaigns, define what counts as net gain and which costs are included. Media spend alone may omit agency fees, discounts, refunds, payment processing, operations and other variable costs.
A worked example
Assume a campaign spends ₹30,000, records 4,000 eligible clicks, generates 200 submitted leads and 150 approved acquisitions. The advertiser's contribution margin from those acquisitions is ₹45,000 before campaign spend.
- EPC from a publisher perspective requires the publisher's commission, not the advertiser's margin.
- CPA from the advertiser perspective is ₹30,000 ÷ 150 = ₹200.
- ROI using ₹45,000 contribution margin is (₹45,000 − ₹30,000) ÷ ₹30,000 = 50%.
The same campaign can have a strong publisher EPC and weak advertiser ROI if the payout is too high relative to downstream margin.
Why context matters
Compare like with like: same attribution window, currency, date range, traffic source, conversion status and cohort. Separate pending from approved commission. Account for reversals and refunds. Do not compare one publisher's EPC from a high-intent content placement with another publisher's EPC from broad paid traffic without segmentation.
Dashboard checklist
Show clicks, unique clicks where meaningful, submitted conversions, approved conversions, rejection reasons, commission, payout status, spend, contribution margin and ROI. Label each metric's formula and refresh interval.
Use EPC to assess publisher monetisation, CPA to assess acquisition cost and ROI to assess economic return. A useful performance review uses all three, with explicit definitions and a consistent data window.
Editorial note: This article is general educational information, not legal, financial or campaign-specific advice. Verify current rules and the actual campaign terms before acting.