Own product · Web & software
Rechnerzentrale
213 calculators for tax, benefits and everyday life – every formula tested against official reference values before it goes live. Our own product.
- calculators for tax, benefits, finance and everyday life
213
calculators for tax, benefits, finance and everyday life
rechnerzentrale.com/llms.txt, as of 8 Oct 2026
- until content is visible (LCP) on desktop, 2.82 s on a phone
0.63 s
until content is visible (LCP) on desktop, 2.82 s on a phone
Lighthouse desktop/mobile, median of 3, 30 Sep 2026
- inputs leave the device – calculations run in the browser
0
inputs leave the device – calculations run in the browser
01Starting point
Online calculators are often slow, full of ads and rarely verifiable. The goal: fast calculators whose results can be backed up – even as laws and values change every year.
02Approach
- 01Calculation logic separate from the interface, every formula with a source.
- 02Golden master tests and a value register against official reference values – they block any release that deviates.
- 03Calculation in the browser: no input leaves the device.
- 04Delivered statically for very short load times, as a PWA and as an Android app on Google Play.
- 05A calculation line on the home page: “19 % von 250” computes instantly, “4000 brutto” opens the matching calculator pre-filled – no server involved.
- 06The same engine also powers client calculators – such as the severance calculator for a transfer company.
03Outcome
A portal with 213 calculators that loads in just over half a second on desktop, with every formula verified before it goes online.
- Next.js
- TypeScript
- Vitest
- Golden-Master-Tests
- PWA
- Android-App (TWA)
A similar task on your desk?
In the intro call we tell you how we would approach it – and how quickly you would see results.