About 17x7

17x7 is a small, independent site of calculators for people whose numbers have consequences: online sellers working out what a sale is really worth, and builders and homeowners ordering materials. The name is the whole idea — a sum you can check.

How we build calculators

Every tool on 17x7 starts from a published source: a marketplace's own fee page, a building code table, a manufacturer's installation guide. We encode the rule once, use the same code for the web page, the API and the agent tools, and test it against worked examples before it ships. The page then shows you every step, so you never have to take our word for the result.

We keep the number of tools deliberately small. Each one gets a real explanation, a worked example, its limits, and answers to common questions. When a source changes — Etsy and Amazon adjust fees regularly — we update the page and the date it was last reviewed.

Independence

17x7 is not affiliated with, endorsed by or sponsored by Etsy, Amazon, Trex, the International Code Council or any other company or body named on the site. Their names are used only to describe what a calculator does. If we ever earn money from a link, the page will say so next to it.

Privacy by design

Calculators run in your browser. We do not ask for an email before showing a result, and we do not set tracking cookies. The privacy policy explains the little we do collect.

Corrections

If a number looks wrong, we want to know. Send the inputs and what you expected; confirmed errors are fixed and noted on the page.

Open-source parts

A few of the developer tools rely on open-source libraries that run in your browser: a cron scheduler and its plain-English describer, a YAML parser and a JSON Schema validator. Their licences and copyright notices are listed in third-party-notices.txt.