PT · Simulador gratuito de amortização antecipada de crédito habitação (Portugal). Compara as duas opções — diminuir prazo e diminuir prestação — lado a lado, com poupança em juros, comissão de reembolso antecipado (regras de 2026) e Imposto do Selo. Todos os cálculos correm no navegador: nenhum dado sai do seu computador.
EN · Free early mortgage repayment (overpayment) calculator for Portuguese mortgages. Compares both options — shorten the term and lower the payment — side by side, with interest savings, the 2026 early-repayment fee rules and stamp duty. Everything runs in your browser: no data ever leaves your machine.
Live: https://natobytes.com/simulador-amortizacao/ (PT) · https://natobytes.com/simulador-amortizacao/en/ (EN)
- Astro 6 static site, React island for the calculator
- TypeScript, Vitest (engine verified against live test vectors)
- GitHub Actions → GitHub Pages
npm install
npm run dev # local dev server
npm test # engine unit tests
npm run check # astro type check
npm run build # static build to dist/French amortization system (sistema francês), monthly rate = TAN/12. The
"next installment" summary replicates the rounding behavior used by Portuguese
mortgage simulators (half-to-even money rounding; the displayed installment is the
sum of independently rounded interest and principal; two-stage half-to-even rounding
of the recomputed term). Lifetime totals come from a full-precision month-by-month
schedule. See docs/superpowers/specs/ for the full verified spec.
Informational only — not financial advice. Figures assume constant Euribor; your contract, FINE and bank price list prevail. Fee rules current as of June 2026.