About Octo Calculator
A free, fast, privacy-first tool collectionOcto Calculator is a growing collection of free online calculators and converters built for everyday use. Whether you need to calculate a tip, convert a hex colour code, work out compound interest, or roll a dice, every tool is designed to give you an accurate result in seconds — no signup, no subscription, no clutter.
Every calculation runs entirely in your browser. Your inputs are never sent to a server, stored in a database, or shared with anyone. The only data we collect is anonymised usage analytics (which pages are visited) to understand which tools are most useful — and only after you consent to that via the cookie banner.
The site is built with Astro and hosted on Cloudflare Pages. Fonts are self-hosted. There are no third-party scripts on page load unless you explicitly grant consent.
Frequently asked questions
Are all the tools free?
Yes, completely. Every calculator and converter on Octo Calculator is free to use with no limits, no account required, and no paid tier. The site is supported by advertising, which only activates if you consent to advertising cookies.
Do you store what I type into the calculators?
No. Every calculation runs locally in your browser using JavaScript. The numbers and values you enter never leave your device — they are not sent to our servers, not logged, and not stored anywhere. When you close the tab, the data is gone.
How accurate are the results?
We work to keep every formula correct and up to date. Results are rounded to a practical number of decimal places and are suitable for everyday use. For financial, medical, or legal decisions, always verify results with a qualified professional or authoritative source. If you spot an error, please use the feedback form below to let us know.
How often are new tools added?
New calculators and converters are added regularly. The site currently covers finance, math, color conversion, binary conversion, and date tools, with more categories planned.
Do the tools work on mobile?
Yes. Every tool is fully responsive and tested on mobile browsers. Number inputs use appropriate mobile keyboards (numeric pad for integers, decimal pad for values with decimal points) so you can use the calculators comfortably on any device.