When I started building CalculaCentro, I had one goal: create a clean, fast, free calculator site in Portuguese that actually works on mobile.
Most calculator sites I found were either in English, full of ads, or broken on phones. Brazilian and Portuguese users deserved better.
What We Built
Over the past months, we've shipped 100+ calculators across categories:
- Finance: compound interest, loan payments, ROI, inflation adjustment
- Taxes: Brazilian IR, INSS, FGTS, MEI, Simples Nacional
- Health: BMI, BMR, calorie needs, ideal weight
- Math: fractions, percentages, rule of three, equations
- Converters: currency, units, temperature
Key Technical Decisions
No frameworks for calculators – Each calculator is a standalone HTML/JS module. This keeps load times under 1s even on 3G.
Progressive enhancement – Works without JavaScript for basic inputs, enhanced with JS for real-time results.
Mobile-first – 70%+ of our users are on phones. Every layout was designed at 375px width first.
What I Learned
- Portuguese SEO is underserved – There's far less competition for Portuguese calculator keywords than English equivalents.
- Users want explanations – The most-visited pages explain how the calculation works, not just the result.
- Speed matters more than features – A fast, simple calculator beats a slow, feature-rich one every time.
Try It
Check out CalculaCentro – fully free, no signup required.
Would love feedback from the dev community on UX, performance, or anything else!
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