sureFIRE

When can I retire? — a free FIRE calculator and net-worth forecaster.

Live app: https://lynchifer.github.io/sureFIRE/

Project your path to financial independence (leanFI · FI · fatFI), pick a retirement age (or let it auto-track the recommended "don't go broke" age), and stress-test the plan against 1,000 fat-tailed market simulations. Model life events — kids, a home (with a real amortizing mortgage), marriage, sabbaticals — and see each one's marginal impact on your FI date.

Your data never leaves your browser. There is no backend and no account; plans persist in localStorage. Don't take our word for it — this is the source.

How it works

Directory	What it is
engine/	Kotlin Multiplatform library — all financial math lives here (projections, tiers, drawdown strategies, Monte Carlo, life-event compilation). JVM target runs the test suite; JS/IR target emits the ESM package (+ TypeScript definitions) the web app consumes.
web/	React + TypeScript + Vite + Tailwind + Apache ECharts front end. A thin boundary (web/src/engine.ts) marshals inputs to the engine — no math in TypeScript.

Everything is computed in today's (real) dollars.

Development

# Engine: run the math test suite (fast, JVM)
cd engine && ./gradlew --no-daemon jvmTest

# Engine: build the JS package the web app imports
cd engine && ./gradlew --no-daemon jsNodeProductionLibraryDistribution

# Web: install & run (after building the engine JS once)
cd web && npm install && npm run dev

After changing Kotlin code, rebuild the engine JS distribution and restart the Vite dev server (clear web/node_modules/.vite if the old package is still cached).

CI / deploy

• engine.yml — runs the JVM test suite on engine changes.
• web.yml — builds the engine JS, lints + type-checks + builds the web, and deploys to GitHub Pages on main.