About 4ny.tools

Who runs this site

4ny.tools is operated under Timo Lutz Medien- und IT-Dienstleistungen, a sole proprietorship registered in Germany. Full contact details and legal information are in the Impressum.

Hi, I'm Timo. Every tool here is selected, tested, and maintained by me — nothing goes live that I haven't used myself. The site is a small, carefully curated collection of calculators and converters — tools that either filled a need of my own or replaced existing online options that were slow, cumbersome, overloaded, or even wanted an email address before they would do arithmetic.

What every tool here promises

  1. Your inputs stay on your device. Every calculation runs in your browser. There is no backend that processes what you type — the server only delivers the page, and using a tool sends no requests, which you can verify in your browser's developer tools. Consent management, analytics, and the contextual advertising described below make their own disclosed requests (see the privacy policy), but they are not part of any calculation. The one exception is the Share feature: if you choose to share a result, the result (and, if you choose, your inputs) is stored in a Cloudflare key/value store, identified only by the returned ID and deleted automatically after 7 days — that is the only time tool data leaves your device, and only when you explicitly ask for it.
  2. It loads fast and stays out of the way. No multi-screen onboarding, no "sign up to see the result", no popup asking for your location before it will convert millimetres to inches. Open the page, use the tool.
  3. The methodology is visible. Every calculator includes a short "How it works" section. For health and finance topics, the relevant page also lists the sources used — peer-reviewed studies, official guidelines, and standard references — so the math can be audited rather than taken on trust.

How content is maintained

Every tool page has the same shape: a short methodology note, a frequently-asked-questions section, and — for any topic where the answer can meaningfully affect health, money, or environmental impact — a list of cited sources. When the underlying studies or guidelines change, the affected pages are revised rather than silently rewritten.

Tools that touch health (Sleep Cycle, TDEE Calculator, Cardio Fitness Score) and finance (FIRE Calculator, Contractor vs. Employee) carry explicit disclaimers. They are informational aids — not substitutes for a doctor, a registered dietitian, a tax advisor, or a financial planner. For an example of the depth I aim for across the site, see the Sleep Cycle Calculator — with full methodology, a limitations section, and cited sleep-science references.

How the site is funded

The site is funded through a small set of affiliate partnerships (Awin, Amazon, financeAds), disclosed on the Affiliate Disclosure page, and through contextual advertising where appropriate. No tool's output is influenced by which partners or advertisers exist, and no tool is gated behind an affiliate link.

About the limits

The site is a one-person operation. Some tools are deeper than others. If a calculator looks wrong, an explanation is unclear, or a source you would expect has been left out, I would rather hear about it than have you quietly close the tab. Corrections, suggestions, and counter-examples are welcome.

Contact