Calculators

A collection of self-contained browser calculators.

Included calculators

• Group Expense Tracker: split shared costs by group, headcount, date ranges, and prior payments. Includes CSV import/export and two sharing modes: snapshot links (data encoded in the URL hash) and optional live cloud trackers (shared at a link anyone can edit, keeping the last 5 revisions).
• Retirement Planner: project savings year by year through retirement and run a Monte Carlo simulation to estimate the probability the plan lasts. Models account types (taxable/traditional/Roth/HSA), taxes, RMDs, Social Security claiming, phased spending, and healthcare/long-term care. Calculation logic lives in retirement-engine.js. See docs/retirement-calculator-plan.md for the design.

Open index.html to start from the calculator landing page.

Calculator data can be shared in two ways. Snapshot links store data in the URL hash using a compact browser-readable format, with no server involvement — best for personal backup, one-off sharing, or static handoff. The Group Expense Tracker also supports live cloud tracker links, which store data server-side and are editable by anyone holding the link. Older compressed snapshot links from development builds still load in browsers that support built-in gzip decompression.

Checks

Run these before committing page changes:

node scripts/check-links.js
node scripts/check-handlers.js
node scripts/retirement-tests.js
node scripts/cloud-client-tests.js

check-handlers.js verifies that every inline onclick-style handler resolves to a function that actually exists — with no build step, a mistyped handler otherwise fails silently at runtime.

The optional cloud backend for the expense tracker lives in worker/ (see worker/README.md and docs/cloud-tracker-plan.md). Its suite needs no install:

cd worker && npm test