Amazonmetrics, explained.

Impressions count each time your product or ad is shown to a shopper, in search results or on another product's page, noticed or not. Amazon's ad reports count your ads alone. Search Query Performance, a report for Brand Registry brands, counts every time you appeared in search results, paid and unpaid together.

CTR is the share of impressions that end in a click. In search results a shopper has little to go on beyond your main image, title, price and star rating, so that is where a weak CTR usually starts. Your bullet points and A+ content do their work after the click.

CPC is what you pay on average each time a shopper clicks your ad, and it's set in an auction against other advertisers bidding for the same spot. If 1 in 10 clicks becomes an order, £1 clicks cost £10 in ads for each sale.

CVR is the percentage of ad clicks that become orders. If you sell through Seller Central, ad reports count orders up to 7 days after a Sponsored Products click and 14 days after a Sponsored Brands one, while unit session percentage covers the whole listing.

Sessions are visits to your product page, and a shopper who comes back within 24 hours still adds only one. Seller Central's Business Reports show them for each product but lump ad clicks in with ordinary visits, so you can't tell which you paid for.

Page views count every time your product page loads, so a shopper who comes back three times in a day adds three page views but one session. Amazon works out your Buy Box percentage from page views rather than sessions.

Unit session percentage is Seller Central's conversion rate for a listing. It counts units rather than orders, so three packs in one order count three times. It also covers visits that didn't come from ads and won't match the conversion rate in your ad reports.

ACoS is ad spend divided by the sales those ads brought in, so £25 of ads that led to £100 of sales is an ACoS of 25%. Amazon reports those sales without value added tax (VAT), so if ACoS is higher than your margin before advertising and before VAT, each sale from an ad is losing you money.

ROAS is ad sales per £1 spent, so £400 from £100 is a ROAS of 4, or a 25% advertising cost of sales (ACoS). Amazon takes value added tax (VAT) out of the ad sales it reports, so work your margin out before VAT too when you check whether the ads pay.

TACoS is ad spend divided by all your sales, including orders that came without an ad click. Because the bottom of the sum is bigger, it normally comes out below your ACoS (advertising cost of sales), so a low TACoS can sit alongside ads that cost more than they earn.

Featured Offer percentage, better known as Buy Box percentage, is the share of your page views where your offer sat behind the Add to Basket button. A drop usually means you've run out of stock or another seller is winning the Buy Box, and Amazon can also hide it over price.

New-to-brand counts ad orders from shoppers who haven't bought your brand on Amazon in the previous 12 months. Ad types such as Sponsored Brands and display ads report it, and a shopper who last bought your brand 13 months ago counts as new again.

Impression share is the portion of all Sponsored Products ad impressions on a search that went to your ads, shown search term by search term in your ad reports. It counts ads only, and a big share can sit alongside a poor organic rank.

Organic rank is where your product sits in the ordinary search results you don't pay for, say fifth on page one for 'magnesium tablets'. Amazon's own reports give you shares and not your position, so brands track rank with outside tools, and it differs for every search and country.

BSR is a product's sales position in its category, where 1 is the best seller. Amazon works it out every hour from recent and past sales, separately in each category and each country's store, so one product can hold several ranks at once.

Search Query Performance is a free report in Brand Analytics, the search data Amazon gives Brand Registry brands, showing your share of impressions, clicks, basket adds and purchases per search. It won't tell you where you sit in the results, but it shows whether you lose shoppers before or after the click.

ODR measures what share of your orders in the last 60 days drew negative seller feedback, an A-to-z Guarantee claim or a card chargeback. Product reviews don't count, but with a 1% limit, two bad orders out of 150 put you over.

Return rate is the share of sold units sent back. In most categories a Fulfilment by Amazon (FBA) product only pays a returns processing fee once its returns pass a threshold set for that category, while clothing, accessories and footwear are charged half the fulfilment fee on returns instead.

Sell-through rate is units sold over the last 90 days divided by the average stock you held at Amazon, so 120 sold against 80 in stock is 1.5. Overstocking drags it down until the extra sells, and you pay storage on it the whole time.

Weeks of cover is how long your stock would last at the current rate of sales. Amazon's storage utilisation surcharge uses its own version, measured by volume across your standard-size stock outside clothing, eyewear, shoes and bags, so one overstocked product can push the lot past 22 weeks.

IPI is Amazon's score for how well you manage Fulfilment by Amazon (FBA) inventory, based on excess stock, sell-through, units with no live listing and keeping products you restock available. It feeds into your monthly capacity limit, and a weak score can mean less room.