What is a KPI?

A KPI (key performance indicator) is a measurable metric used to judge whether a campaign, offer, or traffic source hits a stated target. In affiliate marketing and arbitrage, KPIs are operational funnel numbers: CR, EPC, approval rate, cost per conversion versus payout, and ROI. This page covers those metrics — not employee scorecards and not corporate OKRs.

Search for “what is a KPI” mixes three ideas. OKRs (Objectives and Key Results) are a company goal framework: an objective in words, key results in numbers. People KPIs are sales quotas, call counts, 1:1 scores. Buyer / offer KPIs are the unit metrics that decide whether to scale a funnel, kill a creative, or drop an offer. Only the third meaning belongs here.

Core buyer KPIs

The mix depends on the payout model; the core set rarely changes.

CR (conversion rate) — target actions divided by clicks (sometimes visits). Shows whether traffic monetizes on the chosen offer and landing.
EPC — average revenue per click. Compared with CPC: if EPC stays above CPC, the funnel is profitable before operating costs and hold.
Approval rate — the share of conversions the network or advertiser confirms for payout. Falling approve cuts EPC without changing tracker CR.
CPA / cost per conversion — ad spend divided by conversions. On a CPA offer the funnel works when effective CPA after approve is below payout.
ROI / ROAS — period result: (revenue − spend) / spend or revenue / spend. Without a pending window and status split the number lies.

How the KPIs connect

On fixed CPA with approve counted: EPC ≈ CR × payout × approval rate. Example: CR 2% (0.02), payout $50, approve 80% → EPC = 0.02 × 50 × 0.80 = $0.80. At $0.50 CPC the funnel looks viable; at $1.00 it does not, even if CR “looks fine.” Break-even CR (%) ≈ (CPC ÷ (payout × approve)) × 100. Rising CR with collapsing approve does not save the P&L: the ad account shows more conversions, the network balance shows less.

Revshare and hybrid break the one-day formula: first-day EPC is lower than EPC over weeks if rebills or NGR exist. Split KPIs into short-term (CPA leg, FTD) and delayed (revenue share).

Where KPIs are read

The offer card in an affiliate network publishes EPC and sometimes CR — a network-wide average across GEOs, not a forecast for your funnel. Your KPIs live in the tracker, broken down by campaign, GEO, device, and sub ID (creative, placement, landing). Advertisers watch their own KPIs: qualified leads, FTD, AOV, chargebacks. Gaps of “conversions exist, money does not” usually mean approve and hold, not a “broken postback.”

Common mistakes

Optimizing ad-account CR (pixel/CAPI) while ignoring approved revenue in the network.
Treating published network EPC as a plan for a test budget in a new GEO.
Booking pending conversions as income: until the hold ends, cash ROI is below accounting ROI.
Comparing KPIs across events: signup vs FTD, raw lead vs approved lead — different denominators.
Judging on fewer than 100–200 clicks: EPC and CR jump on small samples.

KPIs by vertical

In gambling the core is CPA per FTD, the share of signups that deposit, and (on revshare) NGR per player. In finance it is approve and cost per approved lead, not cost per raw lead. In nutra COD it is approve after the call center and the delivery/buyout rate. A bare “CR” without the event name is useless: state from what and to what you measure.

Advertiser IOs sometimes fix partner KPI floors (minimum approve, no incent, GEO caps). Those are contract thresholds, not the buyer’s dashboard metrics. This is unrelated to HR scorecards: the network cuts traffic and payout when a floor is missed; it does not “rate an employee.”