About CalcWren
Boring tools, built well. Fast, free, and private by design.
CalcWren is an independent collection of utility tools: calculators, converters, formatters and document templates. Every tool on the site runs entirely in your browser. Your files, figures and form entries never leave your device, because there is no server processing them.
Why these tools
Most utility sites bury simple answers under pop-ups, sign-up walls and upload queues. CalcWren tools load fast, work offline once loaded, and ask for nothing. Each tool is built against real-world test suites and updated when the underlying rules change.
How the site is funded
The site is free to use. In future, unobtrusive advertising may be introduced to cover running costs. Tools will never require payment, accounts or personal data to work.
Feedback
Found something wrong? Every tool page has a Report a problem button, and the feedback form is read by a human. Bug reports with examples get fixed first.