Introducing retplan

Most retirement calculators want your email before they show you a number. retplan starts from the opposite premise: your financial plan is nobody's business but yours, so the entire planner - the projections, the Monte Carlo simulation, even a century of market data - ships to your browser and runs there. There is no account, no server that sees your numbers, and nothing to delete later.

What's inside

The core is a scenario-based retirement modeler. Describe your income, savings, accounts, and spending, and it projects your financial life decade by decade - three ways:

• Deterministic - one clean projection from your expected returns.
• Monte Carlo - thousands of randomized runs that turn "will it last?" into a success rate.
• Historical backtest - your plan replayed against every rolling window of real market history since 1928.

Around the planner sits a growing set of standalone tools: a mortgage early-payoff calculator, the true cost of car ownership, a raising-a-child fund, a subscription audit, box spread loan pricing, and a browsable century of market history.

Statically compiled, aggressively private

The site is a static bundle served from a CDN. Your scenarios live in your browser's local storage; sharing a plan encodes it into a token that only the people you send it to can decode. The tool pages carry ads, which is what keeps everything free - the planner itself has none.

What's next

More tools, deeper writeups on the modeling assumptions, and whatever the feedback asks for loudest. If a number looks wrong, tell us - the fastest way to make a planner trustworthy is to let people check its math.