About Core Compendium

A compendium is a collection of everything worth knowing about a subject, in one place. This one is a collection of tools.

Most free calculators online hand you a number and leave you to work out what it means. Every tool here is built to answer the question you actually came with — what should I charge?, am I losing money?, is this worth making? — and to say so plainly.

How the tools are built

• Private by design. The tools run in your browser. What you type isn't uploaded, stored or sold.
• Checked against the source. Fees and limits come from the official policy pages, and each tool shows the date they were last verified.
• Free, no account. No sign-up wall, no "enter your email to see your result."

How the site is paid for

Some pages link to products or services we think are genuinely useful, and we may earn a commission if you buy through them — at no extra cost to you. Those links never change what a tool calculates. Details are on the terms & disclosures page.

Spotted a mistake?

Fees change. If a number looks wrong, email hello@corecompendium.com and it'll be checked and fixed.