Vanliga frågor (FAQ) — GratisRekenmachine

# Frequently Asked Questions (FAQ)

Common questions about our calculators, accuracy, and privacy.

## Accuracy & Formulas

**How accurate are the calculators on GratisRekenmachine?**

All calculation models and formulas are regularly verified against official standards and regulations:
- Financial calculations: Belastingdienst (Netherlands), HMRC (UK), IRS (USA)
- Health calculations: WHO (World Health Organization), CDC guidelines
- Mathematical formulas: ISO standards and academic benchmarks
- Unit conversions: SI units and international standards

Most calculations are accurate to 2-4 decimal places. For critical financial decisions, always consult a licensed accountant or tax professional.

**What formulas do you use?**

Each calculator uses scientifically recognized, peer-reviewed formulas:
- Mortgage calculation: standard amortization algorithm
- BMI: WHO formula (weight in kg ÷ (height in m)²)
- VAT: European standards per country
- Percentage: ISO 80000 standard

Formula details are available on each calculator page.

## Security & Privacy

**Is my personal data stored or shared?**

No. All calculations happen 100% locally in your browser. We:
- Do NOT store any numbers, input values, or personal information
- Do NOT share data with third parties (not even Google Analytics)
- Use only anonymous traffic statistics
- Fully comply with GDPR/data protection regulations

**Is my browser data secure?**

Yes. All data is processed in your browser sandbox. Nothing leaves your computer. This provides:
- 100% privacy (no server storage)
- Lightning-fast processing
- Works offline (after initial load)

**What about cookies?**

We use minimal cookies:
- **Functional:** Language preference and dark/light mode
- **Analytical:** Anonymous Google Analytics for site improvement
- **Advertising:** Google AdSense for web hosting costs

See our Cookie Policy for full details.

## Features & Support

**Which browsers are supported?**

All modern browsers with JavaScript:
- Chrome/Chromium (version 90+)
- Firefox (version 88+)
- Safari (version 14+)
- Edge (version 90+)
- Mobile browsers (iOS Safari, Chrome Android)

Older browsers may have limitations.

**Can I export or save results?**

Currently you can:
- Copy results to clipboard
- Take screenshots
- Print page (Ctrl+P)

We're evaluating CSV/PDF export for future releases.

**Can I request a calculator?**

Yes! Email mijnrekenmachine@gmail.com with:
- Calculator name
- Description of the calculation
- Use case scenario

Our engineering team will evaluate and potentially build it.

## Languages & Localization

**In how many languages is GratisRekenmachine available?**

We support 8 languages:
- Dutch (nl) - default
- English (en)
- German (de)
- French (fr)
- Italian (it)
- Swedish (sv)
- Norwegian (no)
- Danish (da)

Language is auto-selected based on your browser settings.

**Are calculations the same in all languages?**

Yes. Formulas and calculation logic are identical across all languages. Only interface labels and descriptions are translated.