Which KPIs matter

Amazon Seller Central surfaces dozens of metrics. Most of them are noise for the decisions that actually move an account. RankASIN tracks six — five primary KPIs and a sessions demand signal — chosen because each one responds to a different lever you can actually pull.

Conversion rate (CVR)

Formula: units_ordered / sessions

CVR is the single fastest-responding metric in your account. A listing change — a title rewrite, a new main image, a price test — shows up in CVR within days. Revenue, TACoS, and rank take weeks to reflect the same change.

Typical benchmarks vary widely by category. In skincare, a CVR of 15–20% for a top-of-funnel keyword is healthy. Under 5% suggests a serious listing or price problem. But the category benchmark matters less than your own week-over-week trend: a decline from 18% to 12% in two weeks is a signal regardless of where the category sits.

CVR is why listing optimization happens before ads. If you're converting at 5% and you crank up ad spend, you're buying more sessions for the same poor rate. Fix the listing first.

Buy Box percentage

Formula: sessions_with_buy_box / total_sessions (reported by Amazon as buy_box_percentage)

Buy Box loss is a stealth revenue killer. If you drop from 95% to 70% buy box ownership, roughly 25% of your ad spend is now driving traffic that someone else converts — you pay for the click, a competitor (or a reseller undercutting you) gets the sale.

RankASIN tracks buy box percentage as a weighted average when rolling up across ASINs: weighted by session count, not a naive average of each ASIN's percentage. A high-traffic ASIN at 50% buy box dominates the signal in a way a simple average would hide.

Watch for sudden drops (reseller activity, pricing algorithm misfires, suppressed listings) and gradual slides (competitors undercutting systematically).

TACoS (Total Advertising Cost of Sales)

Formula: ad_spend / total_revenue

ACoS — the version Amazon reports natively — divides ad spend by ad revenue. That number tells you how efficiently your ads are converting. But it misses the most important question: how much of your total revenue depends on ads?

TACoS answers that. A 30% ACoS on campaigns driving 20% of your revenue means your TACoS is 6%. The same 30% ACoS on campaigns driving 80% of your revenue means TACoS is 24%. Those are fundamentally different businesses.

A healthy trajectory is TACoS falling over time while revenue holds or grows — organic rank improving, ads becoming a smaller share of total revenue, the listing standing on its own merit.

Organic share

Formula: (total_revenue - ad_revenue) / total_revenue

Climbing organic share is the endgame of listing optimization. It means your ASIN earns sessions through search rank, not just paid placement. Every point of organic share you gain reduces your cost structure permanently.

Track organic share alongside TACoS — they move together. When TACoS falls and organic share rises, your keyword strategy is working. When both are flat, you're in equilibrium. When TACoS rises and organic share falls, you're buying rank that your listing isn't holding.

Sessions and impressions

Sessions are the demand signal. They tell you whether customers are finding your ASIN at all, regardless of what happens next. Compare sessions week-over-week to catch:

• Sudden drops (suppressed listing, lost buy box, title change that hurt search rank)
• Sustained climbs (keyword rank gains, new PPC coverage, seasonal demand increase)
• Plateaus that suggest a ranking ceiling has been reached

Impressions — where available from Brand Analytics SQP data — show how often you appeared in search results before any click. A high impression-to-session ratio means you're showing up but not getting clicked; the problem is your title or main image.

Unit-aware trend math

RankASIN displays trend deltas next to every KPI — a "+2.3%" badge that tells you whether a metric improved or declined from the prior period. But "percent" means two different things depending on the metric, and conflating them creates misleading signals.

Percent-unit metrics — CVR, TACoS, and Organic share — are already expressed as percentages. When these metrics change, the meaningful number is the absolute percentage-point difference:

• CVR moves from 15% to 17% → displayed as +2.0% (meaning: +2 percentage points)
• TACoS moves from 20% to 17% → displayed as -3.0% (meaning: -3 percentage points)

All other metrics — revenue, units, sessions, buy box — use the relative percent change:

• Revenue moves from $10,000 to $12,000 → displayed as +20.0% (meaning: 20% more revenue)
• Sessions move from 500 to 450 → displayed as -10.0% (meaning: 10% fewer sessions)

Both types display as "+X.X%" in the UI. The number means something different depending on whether the underlying metric is a percentage or an absolute value. This convention is enforced in lib/performance-trend.ts via the computeTrend helper, which checks the metric's unit field before computing the delta.

This matters in practice. A CVR "increase" of +2.0% that is actually +2 percentage points (15% → 17%) is a significant improvement. The same +2.0% as a relative change on a 15% CVR (15% → 15.3%) is noise. Reading the unit tells you which it is.