About

OpenTools is an independent project offering free, practical calculators for everyday work — estimating materials, calculating dates and time, and checking the math behind a decision.

Who it is for

Homeowners, DIYers, tradespeople, students, and anyone who arrives with a concrete task and wants a fast, trustworthy answer with the units and method made clear.

How every tool is built

• Each calculator shows its method and the sources behind its numbers, so you can verify what matters.
• Cost and quantity results are transparent ranges with stated assumptions — never fake-precise quotes.
• Explanatory diagrams are original, and every tool is keyboard-accessible and mobile-first.
• No account is required, and inputs for the published tools are processed in your browser.

How it is supported

OpenTools is free to use. To keep it that way, the site is supported by advertising. The tools are planning aids, not professional, engineering, code, or financial advice — see the Terms for the full picture.