Compound Interest Calculator

Full-stack personal finance app with a .NET API and React SPA.

Current Functionality

API calculators

• POST /api/v1/growth/contribution: compound growth with monthly contributions
• POST /api/v1/growth/savings: compound growth with no recurring contributions
• POST /api/v1/debt/payoff: debt payoff timeline and interest totals
• POST /api/v1/debt/strategy: snowball and avalanche payoff planning for multiple debts
• POST /api/v1/mortgage/estimate: monthly payment and total-interest estimate

Web app tabs

• Interest calculator: UI for growth, debt payoff, and mortgage calculations
• Budget tracker: local-first monthly budgeting and expense tracking
• Debt log: local-first debt ledger, snowball/avalanche payoff planning, CSV import/export, and JSON backup/restore

Tech Stack

• .NET 10 ASP.NET Core Web API with versioning, Swagger, health checks, FluentValidation, and structured logging
• CompoundCalc domain library for deterministic decimal math
• React 18 + Vite + Tailwind SPA served by the API from wwwroot
• IndexedDB persistence for budget and debt-log tab data

Run Locally

1. Restore .NET dependencies:

   dotnet restore

2. Install and build frontend assets:

   pnpm --dir src/web install
   pnpm --dir src/web build

3. Start the API + SPA host:

   dotnet run --project api/CompoundInterestCalculator.Api/CompoundInterestCalculator.Api.csproj

4. Open:
   • App: http://localhost:5032
   • Swagger: http://localhost:5032/swagger

Tests

dotnet test