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Personal Finance

2 tools in the Finance and Business area.

Loan Payoff

Payment, total interest and the full amortization schedule of a fixed-rate loan (mortgage, car loan, student loan or a credit-card balance paid at a fixed amount), and what an extra payment each period does to the payoff date and the interest. The standard annuity formula gives the payment; the schedule is built period by period, so an extra payment, a lump sum or a balloon can be followed exactly. Charts show the balance against time with and without the extra payment and the split of each payment between interest and principal.

Retirement Planner

Retirement savings and withdrawal plan in one currency: a deterministic projection at the expected return (balance by year, the year the money runs out or the terminal balance, the sustainable inflation-indexed withdrawal by the annuity formula) and a seeded Monte Carlo simulation of lognormal annual returns from the stock / bond / cash allocation's means, standard deviations and correlations, or a block bootstrap of Robert Shiller's 1871–2022 annual data or of a pasted return history. Outputs: the probability that the money lasts to the planning age, the percentile fan of the balance by year, the distributions of the terminal balance and of the depletion age, the safe withdrawal rate for a target success probability (Pfau's maximum withdrawal rate of every path), the contribution today that funds the plan with that probability, a sequence-of-returns illustration (the median path with its retirement returns reversed), the sensitivity to ±1 % return, ±10 % spending and retiring two years earlier or later, and the rolling-start historical test of Bengen (1994) and the Trinity study on Shiller's data. Withdrawal rules: fixed real amount, Bengen's initial rate indexed to inflation, a fixed percentage of the balance, and the Guyton–Klinger (2006) guardrails (±20 % bands, 10 % adjustments). Other income (Social Security or a pension) from a chosen age with its own cost-of-living adjustment, a flat tax rate on withdrawals, fees, and the NCHS 2020 life table for the planning horizon. The default case is illustrative: age 40, retiring at 65 with a plan to 95, 200,000 saved, 20,000 a year contributed, 60,000 a year spent in today's money, 60/40 stocks/bonds with the 1926–2010 real-return parameters of Pfau (2011), 10,000 paths; the method reproduces Pfau's published maximum withdrawal rates.

1 worked example reproduced, listed on the tool page.

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