Why bother counting at all
Arbitrage is a business built on a spread: you buy traffic cheaper than the affiliate program pays you for an action. Metrics show whether that spread is positive. If you don't count, you don't know which bundle is feeding you and which one is quietly eating your budget.
Core metrics
CR — Conversion Rate (conversion)
The share of visitors who completed the target action. CR = (conversions / clicks) × 100%. Example: 1000 clicks, 30 deposits → CR = 3%. CR is most heavily influenced by landing page quality — which is why landing page optimization directly multiplies your revenue.
CPC — Cost Per Click (cost of a click)
How much one click costs. CPC = spend / clicks. $50 / 1000 = $0.05 per click.
CPA — Cost Per Action (cost of an action)
How much one conversion costs you. CPA = spend / conversions. $50 / 30 = $1.67 per deposit. CPA should be compared with the payout (how much the affiliate program pays).
EPC — Earnings Per Click (earnings from a click)
How much you earn from a single click. EPC = revenue / clicks. If EPC > CPC, the bundle is in the black. This is the fastest indicator: earnings from a click must be higher than its cost.
ROI / ROMI — return on investment
The headline metric. ROI = (revenue − spend) / spend × 100%. Example: spent $50, earned $90 → ROI = (90−50)/50 = 80%. ROI 0% = broke even, ROI −100% = lost everything.
LTV — Lifetime Value
How much one acquired user brings in over their entire lifetime (important for revshare models in gambling/dating, where they pay not once but from the player's turnover).
A worked bundle calculation
| Metric | Value |
|---|---|
| Traffic spend | $200 |
| Clicks | 2000 (CPC $0.10) |
| Conversions | 40 (CR 2%) |
| Payout per action | $8 |
| Revenue | 40 × $8 = $320 |
| CPA | $200 / 40 = $5 |
| EPC | $320 / 2000 = $0.16 (> CPC $0.10 ✅) |
| ROI | (320−200)/200 = 60% |
The bundle is in the black: EPC is higher than CPC, CPA ($5) is lower than the payout ($8), ROI is 60%. It can be scaled.
What to look at first
Quick rule: EPC vs CPC tells you whether the bundle is alive, even before you calculate ROI. If earnings from a click are lower than its cost — stop, rework the creative or the landing page. The problem is often the landing page itself: raise CR from 2% to 3% and a losing bundle turns profitable. That's why skimping on white page quality is the most expensive mistake.
Calculate your launch cost in a separate guide, and grab landing pages for tests ready-made from the pool — so you don't burn budget on coding too.