Support

Last updated: July 30, 2026

NetMargin calculates the net profit and margin of an Amazon FBA product. It runs entirely in your browser — there is no account, no server, and nothing to sign up for.

Getting started

• On a product page. Install the extension, open any amazon.com product page and click the NetMargin icon. Price, dimensions, weight and category are filled in from the page. Add your cost of goods and inbound shipping to get the real margin.
• Without the extension. The calculator on this site does the same thing — you type the values instead.
• Your whole catalogue at once. Bulk analysis reads the Fee Preview report from Seller Central and ranks every product by margin, using the fees Amazon actually charges you.

A fee looks wrong. What now?

First: every fee is editable. Click the value in the breakdown and type the right one. The line gets marked as edited so you never confuse your number with ours.

The authoritative source for your account is the Fee Preview report in Seller Central (Reports → Fulfillment → Fee Preview). If our number and that report disagree, the report is right — and we would like to know about it.

What we are confident about, and what we are not

• Referral fees — verified line by line against Amazon's published rate card, across all 41 categories.
• Fulfillment, standard sizes — every weight band matches across three independent sources.
• Fulfillment, oversize — sources disagree by up to 8%. The app warns you on screen whenever an item lands in a bulky or extra-large tier. Confirm those against your Fee Preview before pricing.
• Apparel — Amazon publishes that rate card only inside Seller Central, so the app shows the non-apparel rate as a floor and says so.

Known limits

• United States marketplace only.
• Low-season fulfillment rates; peak season (Oct 15 – Jan 14) is not modelled.
• Not included: aged inventory surcharge, removals and disposals, the Overmax surcharge for very large items.
• The fee table in use is stamped on screen ("Fees effective: Jan 2026") so you always know which rate card produced a number.

Reporting a problem

Write to the contact address shown on our Chrome Web Store listing, under Support. A report is most useful when it carries:

• the ASIN, so the product can be checked
• which fee is wrong — referral, fulfillment or storage
• what the Fee Preview report says it should be

Fee corrections go into a new version of the fee table, with a test that pins the case so it cannot come back.

Privacy

Nothing leaves your browser. No account, no analytics, no telemetry. You can verify it: open your DevTools Network tab and use the app. Full details in the privacy policy.