Affiliate income lives or dies at four separate hinge points — how many people see your link, how many click it, how many of those clicks turn into a sale, and how much of that sale you actually keep after refunds. Most back-of-envelope math skips straight from traffic to a dollar figure and lands nowhere close to reality. This calculator walks through all four stages in order, using numbers you can pull straight from your own analytics and affiliate dashboard, so the estimate it hands back is grounded in your actual funnel instead of a guess.
How it works
The engine chains five multiplications and one subtraction, mirroring the path a visitor actually takes. It starts with your monthly traffic and applies your click-through rate to find how many people click the affiliate link at all. That click count is multiplied by your conversion rate to find how many clicks become completed sales. Multiplying that buyer count by your average order value produces total gross sales, and applying your commission rate to gross sales gives the raw commission the program owes you before anything is deducted.
The last step is the one most calculators skip: refunds and chargebacks. Nearly every affiliate program holds commission for a return window and reverses your payout on anything sent back, so the tool multiplies raw commission by (1 - refund rate) to land on a net figure that's much closer to what actually gets deposited. The yearly total is simply that net monthly figure times twelve — computed from the full-precision monthly number before rounding, so the annual estimate doesn't drift from compounding rounding errors along the way.
Worked example
Take a site sending 10,000 monthly visits to a page with affiliate links, a 5% click-through rate, a 3% conversion rate, a $50 average order value, an 8% commission rate, and a 5% refund rate.
- Clicks: 10,000 × 5% = 500
- Buyers: 500 × 3% = 15
- Gross sales: 15 × $50 = $750
- Raw monthly commission: $750 × 8% = $60
- Net monthly commission: $60 × (1 − 5%) = $57
- Yearly commission: $57 × 12 = $684
Nudge the refund rate up to a category with a generous return policy — say 15% instead of 5% — and that same funnel nets $51 instead of $57 a month, a swing that compounds to over $70 a year lost purely to returns nobody accounted for.
How to interpret your result
Read the output as a realistic planning estimate, not a mirror of your next affiliate statement. The math only ever knows what you feed it, and every one of the five inputs is itself an average that moves month to month — a single viral post can spike traffic, a seasonal sale can lift conversion rate, and a product recall can spike refunds well past your typical baseline. Rerun the numbers with a few months of real dashboard data rather than a single snapshot, and treat the result as a midpoint you could reasonably land above or below in any given month.
It's also worth being explicit about what this leaves out. The calculator assumes one flat commission rate for every sale, so it won't capture tiered commission structures that pay more once you cross a volume threshold, one-time performance bonuses, or cookie-window losses where a customer buys after your tracking cookie has already expired. None of those are modeled here, and all of them can move your real number in either direction.
Methodology & sources
The formula is monthlyGross = traffic × CTR% × conversion% × AOV × commission%, then net = monthlyGross × (1 − refund%), and yearly = net × 12, with the yearly figure derived from the full-precision monthly value rather than a pre-rounded one.
Commission rates vary enormously by merchant and product category — Amazon's own Associates commission rate schedule shows rates from 1% on electronics and video games up to 10% on luxury beauty items, with several categories, including gift cards, paying 0% — so the flat rate you enter should reflect the actual program and category you're promoting, not a generic assumption. Separately, running affiliate links at all carries a disclosure obligation: the FTC's Endorsement Guides treat any affiliate commission as a "material connection" that must be disclosed clearly to readers, regardless of the commission rate or dollar amount involved. Neither of those sources sets the refund rate or conversion rate you should use — those numbers come only from your own traffic and sales history, and the more months of real data you use to set them, the more this estimate will look like your actual payout.