About CalcSI

CalcSI is a free collection of 67 useful online tools in 15 languages — built with a clear privacy-first principle: your data stays in your browser.

What is CalcSI?

CalcSI is a collection of 67 free online tools, built between 2024 and 2026 for everyday life, study and daily work. From the MD5 hash generator to Base64 encoders, JSON and XML formatters, CSS generators, color tools and financial calculators (BMI, Schengen stay calculator, building savings, real-estate transfer tax) all the way to 14 interactive OpenStreetMap-based maps — such as defibrillators, EV charging stations or dog-friendly places. All tools are available without sign-up, without limits and in 15 languages.

Our Mission

Many online tools on the web today are overloaded with ads, pop-ups, cookie banners and tracking scripts to the point where the actual function almost disappears. We set out to do better: lean, fast tools that do exactly what they should — without detours, without data collection and without a login wall. A go-to place for anyone who just wants to calculate, format or convert something.

Who is behind CalcSI?

CalcSI is run by the CalcSI Team — a small group of software developers, financial-informatics specialists, and translators with more than 20 years of combined experience in web development, backend engineering, and financial modelling. Our background covers:

  • Software development: PHP, JavaScript/TypeScript, Vue.js, cryptographic APIs (Web Crypto, OpenSSL) and secure hashing schemes.
  • Financial informatics: compound interest, loan amortisation, comparison calculations (e.g. building-savings vs. ETF plans), tax computation and inflation modelling.
  • Health & lifestyle metrics: BMI, TDEE/BMR, body-fat models, caffeine half-life — based on WHO data and peer-reviewed formulae (Harris-Benedict, Mifflin-St Jeor).
  • Geodata & open mapping: OpenStreetMap analysis, data curation, POI filtering and cartographic rendering.

We do not publish personal profiles because CalcSI is an editorial group project — responsibility lies with the operator listed in our imprint. We answer methodology questions by e-mail at [email protected].

How we verify our calculations

Every tool goes through the same editorial process before it goes live:

  • Source research: we start from primary sources — RFCs (e.g. RFC 6234 for SHA-2, RFC 7519 for JWT), W3C/WCAG specifications, tax-law texts, peer-reviewed studies, official statistical data (Eurostat, Destatis, WHO).
  • Implementation: calculations run client-side in your browser. Crypto hashes use the native Web Crypto API; only MD5 is implemented in JavaScript because browsers no longer expose it. No calculation leaves your device.
  • Cross-checking: results are verified against established references — Wolfram Alpha, the OpenSSL CLI, Python libraries, official tax calculators, and WHO BMI tables.
  • Edge cases & limits: we explicitly document where a tool stops being useful (e.g. BMI for athletes, MD5 for security, JWT without key rotation). We do not hide the limits.
  • Update cycle: tax, insurance and inflation calculators are reviewed at least once a year against current legal and data sources. Map data comes directly from OpenStreetMap and is as current as OSM.

Editorial standards

We follow clear rules so you can rely on every calculator and every explanatory text:

  • No bulk AI translations: only German and English are currently active. Additional languages will only be unlocked after a native-speaker reviewer has signed off on the translations.
  • Transparency over affiliate pressure: CalcSI contains no affiliate links to banks, brokers or providers. Comparisons follow official conditions, not commissions.
  • Not medical, tax or legal advice: our health and finance tools provide orientation values. For important decisions they do not replace a doctor, tax advisor or lawyer — and we say so explicitly on every relevant page.
  • Corrections are visible: if we correct a formula or a dataset after publication, we document it in a blog post and update the timestamp of the relevant tool page.

Privacy First

Privacy is not a marketing word for us, it is architecture. Practically all calculations — hashes, encoders, formatters, color conversions, financial calculators — run entirely client-side in your browser. Your text, your JSON, your password never leaves your device. We do not set tracking pixels or advertising profiling cookies, apart from consent-based Google AdSense ads that fund the site. And there too: no ads without explicit consent.

What Makes Us Different

In concrete terms, this means for you as a user:

  • 67 tools in one place — from cryptography and encoding to CSS generators and financial or map tools.
  • 15 languages, all maintained — not just machine-translated and forgotten, but treated as equal versions.
  • No login, no limits — you do not have to sign up and there are no artificial usage caps.
  • No data transfer for calculations — your input stays in your browser.
  • 14 OpenStreetMap-based maps with live data — from defibrillator and EV charging maps to dog-friendly places.
  • Open to feedback — we are happy to hear about issues, improvements or tool suggestions.

Why Is CalcSI Free?

To keep all tools permanently free and available without login, we show unobtrusive ads via Google AdSense — only if you have consented to the corresponding cookie category, of course. These ads fund hosting, domain, licenses and the ongoing maintenance of the 15 language versions. There is no premium tier, no paid features and no paywalls: what you see is everything, and it is free for everyone to use.

Who Is Behind CalcSI?

CalcSI is operated by an independent developer based in Germany. Behind the project is the wish to make the open web a slightly friendlier place: useful tools, multilingual, without dark patterns. You can find the legal entity and contact details in the imprint; for technical questions, bug reports or tool suggestions please use the contact page.

Feedback & Tool Suggestions

Missing a particular tool? Spotting a bug, a poor translation or a typo somewhere? Got an idea for a new map or calculator? We are happy to hear from you and regularly add suggestions to our roadmap. Drop us a message via [email protected] or via the contact page.

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