199 calculators · DE/EN
Rechnerzentrale
Calculators for tax, benefits and everyday life – every formula tested against official reference values.
- Next.js
- Golden master tests
- PWA
Service D · Web & software
Software that’s there before you wait.
Websites, web apps and business software – fast to load, accessible, bilingual and with tests that check every formula against reference values.
01What we build
From website to business software.
01
Company websites
Sites that load fast, get found and are easy to maintain.
- Next.js, statically delivered
- Search and AI visibility
- Accessible to WCAG 2.2 AA
02
Web apps & business software
Tools for processes that live on paper or in spreadsheets today – in the browser and as an app.
- Forms, inspection records, PDF generation
- Offline-capable as a PWA
- Roles, logins, hosted in Germany
03
Integrations & operations
Connections to existing systems, hosting and monitoring – so it keeps running after launch.
- APIs, data imports, automation
- Monitoring and updates
- Further development as needed
02Measurably fast
Load time is not a matter of faith.
We measure how long it takes until the main content of a page is visible (Largest Contentful Paint). Our own sites are well under a second – and this page is measuring itself in the footer right now.
↓ Measured live: see footer
- Aphantasie0.69 s
Lighthouse desktop, 24 Sep 2026
- Rechnerzentrale0.55 s
Lighthouse desktop, 24 Sep 2026
- headon.pro (alt)3.00 s
Lighthouse mobile, 24 Sep 2026
03Quality
Tested before it goes live.
01
Tests against reference values
At Rechnerzentrale every formula is tested against official reference values before it goes online.
02
Accessibility
Keyboard use, contrast, screen readers – to WCAG 2.2 AA, as required by the European Accessibility Act.
03
Bilingual
German and English with clean language versions – for search engines and people.
04
Visible in search and AI
Structured data, fast pages and clear content that AI assistants can cite.
04Technology
Proven, not fashionable.
We choose technology by task. Our default is a stack that lets us deliver quickly and safely.
- Next.js
- React
- TypeScript
- Tailwind CSS
- Supabase
- PostgreSQL
- Vitest
- Playwright
- WordPress or Next.js?
- WordPress when many editors maintain content without developers. Next.js when speed, security and custom features matter.
- Website or web app?
- A website informs, a web app gets work done. Many projects need both under one address.
- App store app or PWA?
- A PWA is enough for most business applications – installable, offline-capable, no store approval.
05Work
In use, not on paper.
5 days
Digital PPE inspection record
From paper form to inspection app with a QR code per device, signature and PDF.
- Web app
- PWA
#1 for “aphantasie test”
Aphantasia
Test portal with eight scientific tests in five languages. Our own product.
- Next.js
- Five languages
06Process
Short paths, clear steps.
01
Intro call
Clarify goal, scope and constraints – 30 minutes, free.
02
Quote
Fixed price for the agreed scope, with a schedule.
03
Draft
A clickable version after a few days instead of weeks of layout PDFs.
04
Build
Development with tests, accessibility and a load-time budget.
05
Launch & care
Go-live, monitoring and further development as needed.
07Formats
Fixed price, before we start.
Fixed price
Company website
Up to about eight pages, fast, accessible, with search fundamentals.
Fixed price per stage
Web app / business software
From prototype to production – e.g. digital inspection records.
Fixed price
SEO & AI visibility audit
Technology, content and structured data reviewed, with a prioritised list.
Monthly
Care plan
Hosting, updates, monitoring and small changes.
08Fragen
Frequently asked.
How long does a website take?
A company website with a clear scope is often ready within a few weeks, a first clickable version usually after a few days. We set the schedule in the quote.
Can we edit content ourselves?
Yes. Depending on your needs via a CMS or simple content files – we show you both and recommend what suits your team.
Where is data stored?
We run websites and applications on servers in Germany and choose EU regions for databases. Details are in the quote and the data processing agreement.
Do you take over existing websites?
Yes – for maintenance, accessibility, load time or a relaunch. We review what exists first and tell you honestly whether to rebuild or refactor.
What should your software get done?
Describe the process that costs time today. In the intro call we sketch what a solution could look like – and what it costs.