Affiliate marketing drowns in acronyms, but only a few metrics genuinely matter. Having read these numbers as an affiliate deciding where to spend my effort, as a manager judging partners, and as the person who built the reports both sides stared at, I can tell you which ones to watch and which are noise.
Here are the core affiliate marketing metrics, what each one means, the simple formula behind it, and how the two sides of a deal should read it.
The metrics that actually matter
You can ignore most of a dashboard. The numbers that drive real decisions are conversion rate, EPC, average order value, the cookie window, and the reversal rate. Master those five and everything else is context.
One caveat before the definitions: make sure both sides measure the same thing. Terms like a “conversion” or even a “click” can be defined differently by different platforms, which is why industry bodies such as the IAB publish measurement standards. When your figures and a partner’s don’t line up, a definition mismatch is often the cause — rule that out before deciding anyone’s number is wrong.
Conversion rate (CR)
Conversion rate is the share of clicks that turn into the action you’re paid for — a sale or a lead. The formula is simple:
CR = conversions ÷ clicks × 100. If 1,000 clicks produce 20 sales, that’s a 2% conversion rate.
For affiliates, a low CR points at a mismatch between your traffic and the offer, or a weak landing experience. For merchants, CR is a signal about the offer and checkout, not just the affiliate — if every partner converts poorly, the problem is usually yours.
EPC: earnings per click
EPC is the metric I trust most, because it folds conversion rate and commission into one number: how much you earn, on average, for every click you send.
EPC = total commissions ÷ total clicks. Earn $100 from 200 clicks and your EPC is $0.50.
EPC is how you compare two offers fairly. A program with a lower commission but a much higher conversion rate can out-earn a flashy high-rate offer that never converts. Merchants quote EPC to recruit affiliates for exactly that reason — it’s the number partners care about.
AOV and commission
Average order value (AOV) is total revenue divided by number of orders. It matters because your commission is usually a percentage of it: the same 10% rate pays far more on a $300 basket than a $30 one. When you weigh a niche or a program, AOV and commission structure together decide the ceiling on your earnings — a point we cover in depth in commission and payout models.
AOV also explains why some low-traffic niches out-earn busy ones: a handful of high-value orders can beat thousands of tiny ones. It’s why I always check AOV and commission before judging a niche on search volume alone — volume without value is a trap that looks like opportunity.
Cookie window and its effect
The cookie window is how long after a click you can still be credited for a sale. It doesn’t appear as a single figure on most dashboards, but it quietly shapes all the others: a longer window captures more delayed purchases, lifting both conversion rate and EPC. For considered, expensive purchases it can matter more than the headline commission. The mechanics sit inside how affiliate tracking works and attribution models.
Reversal and approval rate
Not every recorded sale becomes paid commission. Returns, cancellations and fraud checks reverse some of them. The reversal rate is the share that gets clawed back; the approval rate is what survives. A pending commission figure can look great and then shrink at approval, so both sides should judge performance on approved earnings, not gross.
Read the net number. A partner with slightly fewer sales but a far lower reversal rate is often the more valuable one. Gross totals flatter; approved totals tell the truth.
EPC vs CR: which should you optimise?
Conversion rate tells you how well traffic and offer fit; EPC tells you what that fit is worth. If you have to pick one to optimise, pick EPC — it’s the number that pays your bills. Use CR and AOV to diagnose why your EPC is where it is. Affiliates should rank offers by EPC; merchants should quote it honestly to recruit, and watch approved EPC to keep partners happy. When you’re comparing platforms that report all this, our tracking software reviews look hard at how clearly each one surfaces these numbers, and the wider affiliate and merchant tracks put them in context.
Frequently asked questions
What is a good EPC in affiliate marketing?
There’s no universal figure — EPC varies enormously by niche, price point and traffic quality. Rather than chase a benchmark, compare EPC between the specific offers you can actually promote, and track whether your own EPC is trending up over time.
What’s the difference between EPC and conversion rate?
Conversion rate is the percentage of clicks that convert; EPC is the average earnings per click. EPC combines conversion rate and commission into one money figure, which makes it the better number for comparing offers.
Why are my pending commissions higher than what I get paid?
Because of reversals. Returns, cancellations and fraud checks remove some conversions after the fact, so approved commissions are usually lower than the pending total. Always judge performance on approved earnings.
Which affiliate metric matters most?
EPC, for most decisions, because it reflects real earnings per click. Use conversion rate and average order value to understand what’s driving your EPC, and the reversal rate to make sure the number is net, not gross.
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