About page reviewed September 2026
ERICH Calculators is a free reference site built around a simple idea: make common calculations easy to find, easy to use and easy to understand.
The library covers money, math, dates, business, construction, school, health, conversions and other everyday topics. Calculators are supported by topic hubs and practical guides so visitors can understand the method instead of seeing only a number.
The current tools run directly in the browser using JavaScript. Calculator pages show formulas, examples and assumptions where practical. For areas where an outside standard or authoritative reference matters, source links are added to the relevant pages.
We test calculation logic and work to keep assumptions visible. No calculator can account for every real-world circumstance, so important financial, legal, tax, payroll, construction or health decisions should be independently verified.
Read the full Calculator Methodology & Accuracy page for details about formulas, sources, browser processing and corrections.
If you find a result that looks wrong, please send the calculator URL, your inputs, the result you received and the result you expected. We also welcome suggestions for useful new calculators and guides.