About Sellarithm

What Sellarithm is

Sellarithm is a small set of free calculators built to answer one practical question that most sellers ask before they list anything: if I sell this at this price, what do I actually keep?

Marketplace fees are rarely a single number. Between listing fees, transaction fees, payment processing, optional advertising fees, and your own costs for materials, packaging and shipping, it's easy to price a product without a clear picture of what's left over. Sellarithm exists to make that math visible before you hit "publish" on a listing, not after you've made your first sale and wondered where the money went.

Why calculators, specifically

Spreadsheets work, but most sellers don't want to build or maintain one for every pricing decision. Sellarithm's tools are built to do one job well each — profit, pricing, fees, margin, break-even, ROI, discounts, shipping economics, ad costs, sales goals — rather than one large, complicated all-in-one tool that tries to do everything at once.

Every calculator shows its assumptions and its fee rates directly on the page, and every result is labeled as what it is: an estimate based on the numbers you enter and the fee profile the calculator uses. Sellarithm is not connected to your shop and doesn't know your actual account terms, so it can't guarantee that its output matches what a marketplace deposits into your account.

Who this is for

Sellarithm is built for people who sell things online and want a faster, clearer way to check their pricing and profit — from someone testing their first product idea to a seller with an established shop who wants to sanity-check a new listing or a seasonal discount.

Starting with Etsy, built to grow

The first 13 calculators on Sellarithm are built specifically around Etsy's fee structure, because Etsy sellers face a particularly layered set of fees that are easy to underestimate. That's a deliberate starting point, not the whole plan — the same profit-and-pricing logic applies to Amazon, Shopify, eBay, print-on-demand, digital products and handmade sellers on other platforms, and Sellarithm is built to expand into those fee structures over time.

Independence

Sellarithm is an independent website. It is not affiliated with, endorsed by, or sponsored by Etsy, Inc. or any other marketplace referenced on this site. Etsy fee rates used in these calculators are based on Etsy's publicly published seller fee information at the time each calculator was last checked, and are provided for estimation purposes only. Marketplaces change their fee structures from time to time, so always confirm current rates directly with the platform before making a pricing decision. See the Disclaimer for more detail.

A note on who's behind this

Sellarithm is an independently built and maintained project. It isn't a large company with a support team, and it doesn't claim credentials or industry awards it hasn't earned. If something on the site is wrong, unclear, or could be more useful, the fastest way to help fix it is to get in touch.