About

retplan is a free, browser-based financial planner. Its core is a retirement modeler: describe your income, savings, accounts, and spending, and it projects your financial life decade by decade - deterministically, through Monte Carlo simulation, and by replaying your plan against roughly a century of real market history. Around the planner sits a growing set of standalone calculators for specific money questions: financing a purchase with a box spread instead of a consumer loan, the all-in cost of owning a car, funding the cost of raising a child, paying a mortgage off early, laddering Roth conversions through the low brackets, auditing subscriptions, and exploring market history directly.

Everything computes in your browser. There are no accounts, and the numbers you enter stay on your device - plans are saved locally and can be shared only by links you create yourself. The market dataset ships with the site, so even the backtests run offline.

retplan is an independent project. The standalone tool pages show advertising, which is what keeps the site free; the planner itself carries no ads.

One important limit: retplan is an educational modeling tool. It illustrates how assumptions play out, but it does not know your full situation and is not financial, investment, tax, or legal advice. For decisions that matter, consult a qualified professional.