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Saving and Planning

10 tools in the Investing area.

Compound Growth and Fees

How saving, time, return and fees combine. Enter a starting amount, a regular contribution, the years, an expected yearly return, the yearly fee and inflation; the page works out the future balance step by step with and without the fee, what the fee costs in money and as a share of the final balance, the same in today's money, how much of the balance is money paid in and how much is growth, a year-by-year table and a table of the final balance against the fee and the return. Advanced mode adds contributions that rise each year, a tax drag, a lump sum against spreading it in, the Rule of 72 and the contribution needed to reach a target. A calculator for education and analysis, not investment advice.

1 worked example reproduced, listed on the tool page.

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.

Capital Gains and Tax Lots

Which purchase lots a sale takes, and the gain or loss that results. Paste the lots (date, shares, cost per share), enter the sale and choose a lot method; the page shows the lots taken, the gain or loss on each, whether it is short-term or long-term under the one-year holding rule of IRS Publication 550, the totals, the tax at two rates you enter, the lots that remain, and the same sale under every method side by side. Advanced mode adds a wash-sale check against other purchases, the average-cost method of mutual funds and a sale commission. The page describes U.S. federal rules as general facts; it is an illustration, not tax advice. A calculator for education and analysis, not investment advice.

1 worked example reproduced, listed on the tool page.

Personal Rate of Return

What did my account actually earn? Enter the opening and closing value of an account with their dates and paste the deposits and withdrawals in between; the page works out the gain in money and three rates of return step by step: the money-weighted return (the internal rate of return of the dated cash flows, the figure a spreadsheet calls XIRR), the time-weighted return when the account value at each deposit or withdrawal is given, and the Modified Dietz approximation, and it explains why they differ. Advanced mode adds the value the same deposits would have reached at a benchmark return and the effect of fees paid from outside the account. A calculator for education and analysis, not investment advice.

1 worked example reproduced, listed on the tool page.

Inflation Calculator

What an amount of U.S. dollars from one year is worth in another. Enter an amount and two years; the page looks up the Consumer Price Index for All Urban Consumers (CPI-U) of the Bureau of Labor Statistics for both, which runs from 1913, and works out step by step the equivalent amount, the cumulative inflation, the average yearly rate and what the original amount still buys, with a table every fifth year and charts of the index and of yearly inflation. Advanced mode compares single months, turns a nominal return into a real return and carries the index past the published data at an inflation rate you assume. A calculator for education and analysis, not investment advice.

1 worked example reproduced, listed on the tool page.

Traditional versus Roth

Which retirement account leaves more after tax: a Traditional account, where the money goes in untaxed and is taxed when withdrawn, or a Roth account, where the money is taxed now and withdrawn tax free. Enter an amount, the years to withdrawal, a return and two tax rates you choose; the page works both out step by step, shows why they are equal when the two rates are equal, the difference in money and percent, the break-even retirement tax rate, and a table and chart across retirement tax rates. Advanced mode adds contributing the same dollar amount to each, an employer match, a contribution every year, converting an existing balance and an early-withdrawal penalty rate. The page describes U.S. federal rules as general facts of IRS Publications 590-A and 590-B; contribution and income limits change every year and are not included. It is an illustration, not tax advice. A calculator for education and analysis, not investment advice.

1 worked example reproduced, listed on the tool page.

Social Security Claiming Age

The monthly U.S. Social Security retirement benefit at each claiming age from 62 to 70, and the ages at which a later claim catches up with an earlier one. Enter the benefit at full retirement age from your Social Security statement, your year of birth, an assumed cost-of-living increase, a discount rate and the age the comparison runs to; the page finds the full retirement age, writes out the reduction for claiming at 62 and the credit for waiting to 70, tabulates the benefit at every claiming age, and gives the break-even ages and the present value of each choice. Advanced mode computes the benefit from average indexed monthly earnings with the bend points you enter, and adds a spouse with the survivor benefit. The rules are quoted from the Social Security Administration's regulations; the page describes them and does not say when to claim. It is an illustration, not tax, legal or benefits advice. A calculator for education and analysis, not investment advice.

1 worked example reproduced, listed on the tool page.

Required Minimum Distributions

The yearly withdrawal that U.S. federal rules require from a tax-deferred retirement account such as a traditional IRA, and how the account runs down under it. Enter the balance at the end of last year and the owner's age; the page divides the balance by the factor of the IRS Uniform Lifetime Table (Publication 590-B, edition for 2025 returns), then projects the balance, the required withdrawal, the tax at a rate you enter and the amount left after tax, year by year. Advanced mode adds a spouse more than ten years younger (this year only, from the Joint Life factor you enter), an inherited account under the ten-year rule, a qualified charitable distribution and withdrawals above the minimum. The page states the rules as general facts of that publication; it is an illustration, not tax advice. A calculator for education and analysis, not investment advice.

1 worked example reproduced, listed on the tool page.

Pay Off Debt or Invest

An extra sum each month can prepay a loan or be invested. Enter the loan balance, its rate and the months left, the extra per month, an expected investment return and the years to compare; the page follows both paths month by month with the same money leaving the budget in each, and works out step by step the payment, the interest and months that prepaying saves, the net worth of each path at the end, the difference, and the break-even investment return with the reason it equals the loan rate. A table shows the difference across returns and a chart shows both net-worth paths. Advanced mode adds tax-deductible interest, tax on investment returns, an employer match and the probability, under a lognormal model of returns, that investing ends ahead. A calculator for education and analysis, not investment advice.

1 worked example reproduced, listed on the tool page.

Rent versus Buy

Compares buying a home with renting an equivalent one, in money. Enter the price, down payment, mortgage rate and term, the rent, how long you expect to stay and three yearly rates (home appreciation, rent increase, investment return); the page works out step by step the cash needed to buy, the mortgage payment, the monthly cost of each choice, the net worth of the buyer (home equity after selling costs) and of the renter (the same cash invested) year by year, the break-even year when buying pulls ahead, and the unrecoverable cost of each choice per year. Advanced mode opens the fixed assumptions: property tax, maintenance, insurance, buying and selling costs and the income-tax treatment. It describes the two paths under the rates entered and does not say which to choose. Tax effects are an illustration, not tax advice. A calculator for education and analysis, not investment advice.

1 worked example reproduced, listed on the tool page.

Other Investing sections

Economy and Rates · Company Financials · Stock Valuation · Portfolio and Risk · Bonds · Options · Mergers and Buyouts · Private Markets