About SellerSpec

A reference for the measurements and fee maths that people selling printed and digital products need to get right the first time. Written and maintained by Ali Taab Baloch.

Who writes this

I'm Ali Taab Baloch. I sell digital printables on Etsy under ATBServices, publish paperbacks through Amazon KDP, and run ATB Services LLC, an Amazon FBA wholesale account management business. I also write at alitaab.com about wholesale, TikTok Shop and the operational side of running these businesses.

That matters here for one reason: every number on this site is one I have needed myself. The cover geometry is what I use to build print files. The paper dimensions are what decide whether a printable crops on a customer's printer. The fee maths is what decides whether a listing is worth publishing. This is not a survey of a topic I read about — it is the reference I wanted and could not find in one reliable place.

Why it exists

Three kinds of number cause a disproportionate amount of wasted work for small sellers: cover geometry that gets a print file rejected, paper dimensions that crop a customer's printable, and fee maths that quietly turns a sale into a loss.

All three are fully determined — there is a correct answer, and it can be computed. Yet the answers online disagree with each other constantly, because they get copied between articles instead of taken from the specification.

The book spine formula is the clearest case. The version reproduced by most calculators and tutorials adds 0.06″ to page count times paper thickness. Amazon's own specification contains no such constant. That extra 0.06″ makes a finished cover about 1.5 mm too wide — enough to shift spine text visibly off-centre. I found this the way most people do, by having a file come back, and then by reading the actual specification instead of the fourth blog post about it.

So this site does the boring thing: one stored value per fact, traced to its source, dated, with everything else computed from it. The methodology page sets out exactly how, including the parts that are not automated.

How it is funded

Free to use, with no account and no paywall. Where the site links to a product or service it may earn a commission, and any such link is marked. I also sell digital products of my own — those are the two links in the section above, and I have kept them out of the reference pages deliberately.

Commission never determines what is recommended, and no marketplace or vendor has any say over the figures published here. If a fee schedule makes a platform look bad, that is what gets published.

Corrections

If a number here is wrong I want to know, and fixing it at the source fixes every page that derives from it at once. Changes are logged publicly in the data changelog, including what was wrong and why.

Independence

SellerSpec is not affiliated with, endorsed by or operated by Amazon, Etsy, eBay or any other marketplace. Their names are used only to identify whose published schedule a figure came from. My own selling accounts on those platforms give me no access or standing beyond any other seller's.