RemWorth Lens · browser extension · its own product · included with any subscription
On any amazon.com product page, Lens shows what every calculator shows — profit, ROI, fees, rank, history. Then it shows what no standalone extension ever can: whether you've bought this exact ASIN before, how many units you have on hand right now, and what you really paid — your true FIFO cost, one click from being the buy cost in the calculator. A standalone extension can't copy that. It has no ledger to read. $9.99/mo standalone; included with any RemWorth subscription.
Standing at a shelf, or fifty rows deep in a storefront: have I bought this before? What did I pay? Do I still have units at FBA? Your calculator extension can't tell you — it has no ledger to read. It charges you a second subscription for history charts on top. And it stores your buy costs and notes in the browser, warning you in its own words that they don't sync across devices. You're sourcing against your own memory, on rented data, in a tool that admits it forgets.
While you're on the listing, Lens reads your actual RemWorth ledger: bought-before or not, units on hand right now, true FIFO cost per unit — the same figure the rest of RemWorth uses, so the widget and your P&L can never disagree — lifetime units sold, last-sold date. One click drops your real historical cost into the calculator: "Use $X.XX as buy cost." Never touched the ASIN? It says so, plainly. Every other number in a sourcing widget is public data any tool can fetch. This one comes from your accounting, and only ours has your accounting.
Full price-and-rank history on every product, served through RemWorth's own data service — no separate market-data subscription to buy, no key to babysit, no per-lookup charges while you hunt. The chart is embedded in the widget: 30 to 730 days, eleven toggleable series — Amazon price, 3rd-party new, FBA/FBM, Buy Box, used, sales rank, offer count, units sold, rating, review count — with an optional inverted rank axis if that's how you read rank. Is today's price real, or a spike somebody's about to tank? Two years of history answers it, and the answer stopped costing extra.
A profit widget under the title on any amazon.com product page: type a sell price and a buy cost, and net profit, ROI, and margin recalculate on every keystroke. Fee bands follow the sell price as you type — Amazon's fulfillment fee changes below $10, $10–50, and above $50, and the widget picks the right band live instead of locking to the page price. Price at $9.49 to undercut and you'll be charged the sub-$10 fee; your calculator should know that before you do. Breakeven price and Max Buy Cost compute against your own rules — minimum net dollars, ROI %, or margin % — because in the aisle, "the most I can pay" is the only number you act on. Side-by-side target tables show min sell price and max buy cost at each target you define ($0/$1/$2, or 0/10/15%): the supplier quotes three case prices, and you see at a glance which one is a deal and which is charity.
Referral fee with the $0.30 minimum, FBA fulfillment by size tier and price band, variable closing fee, inbound placement, monthly storage — itemized, with size tier, program, and season shown so you can see WHY the fee is what it is. The rate tables carry recorded effective dates and are maintained as tables, not scraped from help pages — so Lens doesn't break the week Amazon rewords a sentence. With a connected account, the referral rate for that exact ASIN comes straight from Amazon instead of a category table, and the data source is labeled either way. Cost realism is yours to set: buy-side tax, editable prep chips (bag, tape, label, bubble), storage months, catch-all per-unit costs, and a configurable ROI method — buy cost alone, plus other costs, or plus inbound — so ROI computes the way YOU compute it.
No dimensions on file? No buy cost entered? No fulfillment fee available? The cell shows a labeled gap with the reason on hover — never an invented ~$3 fee that turns a loser into a "winner" somebody buys forty units of. The demand stats hold to the same standard: current rank and category live from the page, rank drops over 30/90/180 days with an optional 3%-threshold mode so wobbles don't count as sales, average rank per window, Amazon's own "bought in past month" figure, and Amazon's out-of-stock percentage over 30 and 90 days. Demand data with a source, not a vibe.
Gating: one click asks Amazon directly, on your own connected account — restricted or can-sell for YOUR account, Amazon's reason messages on hover, "unknown" reported honestly when the check can't complete. Never a false green. It runs on demand — only when you ask; without a connection the widget still works, and this one check names what's missing. A hazmat tier and battery flag with the underlying reason codes rides along. The verdict is the scope — the approval application is yours to file. Offers: one click opens every seller — FBA/FBM/Amazon badge, condition, price, stock count, Buy Box win share, feedback — live offers sorted first so a dead offer at a great price can't fake the floor; columns configurable; loads only when opened. A summary strip counts the offers within your set % of the low FBA price: the set you'd actually be pricing against. Variations: every child ASIN with its own rank, monthly sold, Buy Box price, low FBA, and offer count — up to 100 in one batched lookup, the current one highlighted, each linked. The parent looks great; only black/medium sells. See that before you buy the size run. No variations? It says so plainly.
On Amazon search pages and seller storefronts, Lens paints a compact strip under every tile: rank, 30-day rank drops, monthly sold, FBA offer count, and combined referral + FBA fee at the tile's listed price. One batched call per page of results, keeps up with infinite scroll, toggleable per surface. And deliberately: no ROI on tiles. Without a buy cost, an ROI would be fiction — so we don't print one.
The buy cost you type, the note you jot, the star you tap — saved to your RemWorth account, not the browser. Buy costs auto-save per ASIN and reload on any device. Notes sync. Star up to 500 keep-for-later ASINs. Everything saves on blur; there is no save button to forget. Competing extensions store this in the browser and warn you, in their own words, that it doesn't sync across devices.
Outbound postage estimated from a real USPS Ground Advantage Commercial rate table by weight and zone — zones 1–8, to 10 lb — with length and cubic-foot surcharges applied automatically and USPS's 2026 sub-pound pricing rule built in. A ship-revenue field for what the buyer pays you; simpler $/lb or flat-rate models if you prefer. Anything outside the table — zone 9, over 10 lb, Priority Mail — refuses by name rather than extrapolating a wrong number into your margin. Under one flat shipping guess, half an FBM seller's "profits" are fiction. Not here.
The calculator reproduces the output of the profit-calculator extension sellers already know, cell for cell — on day one you see the exact numbers you're used to, because unfamiliar math is the real reason switches fail. Then import the settings export from the extension you're leaving: every key is either mapped onto Lens or listed with the stated reason it doesn't apply — nothing silently dropped. The import is tested against a real settings export from the leading competitor. Underneath, eight settings tabs keyed per marketplace — FBA costs, Merchant, Pricing, Targets, Display, Variations, Links, Data — cover every assumption: inbound $/lb regular and hazmat, placement fees by region and split count, storage months, prep chips, buy-side tax, target lists, per-channel Max Buy Cost rules, widget position (9 spots), font size, stat rows, column sets, default sell-price source order — plus named configurations and settings export/import for a backup or a second machine.
Copy a tab-separated, paste-straight-into-a-grid row to the clipboard, or download a CSV with your exact pick of 35 fields — identifiers, rank stats, prices, every calculator output, fees, dimensions, offer counts. A "Withheld" column travels with every export, so a blank profit cell in your buy list is never mistaken for a bad product a week later. The honesty follows the data into your own spreadsheet. Custom research links round it out: one-click links to the shopping and price-history sites you cross-check, plus any link you define with template variables (TITLE, TITLE6, ASIN, UPC, ISBN10, ISBN13, MODEL), per marketplace — and a link that needs a fact this product lacks shows disabled with the reason, instead of silently vanishing.
Sign in to the RemWorth web app in the same browser and Lens connects itself — and disconnects on logout. Permissions are minimal: it runs only on amazon.com and the RemWorth app, with no access to your other tabs or browsing. Your seller account is your livelihood; an extension that wants everything is a hard no, and we agree. Install is the normal kind: Lens is on the Chrome Web Store. One click to add it, and it connects itself the moment you're signed in to RemWorth in the same browser.
The bill math
Standalone: $9.99/month. With any RemWorth subscription: included. A switcher typically drops two bills — the old calculator extension and the data subscription it needed for charts — for at most one.