How it works

1. Set your timeline

Enter your current age, your first full year without employment income, and how far you want the plan to run. Add your partner to model separate ages and work schedules. Future years are aligned to the plan’s start year and your age.

2. Describe everyday finances

Enter yearly pay before taxes and your base monthly spending. Put predictable ongoing costs in that spending figure. Use life events for additional or time-limited costs, and avoid including the same expense twice.

Cash, brokerage and retirement accounts are separate. Pre-tax and Roth balances and contributions can be entered in Advanced or Quick’s optional assumptions. Cash set aside as a reserve is not available to fund spending; the alternative cash setting allows it to cover shortfalls first.

3. Choose your assumptions

Steady return

Applies the chosen annual investment return unless a year has an override. New Quick plans start at 6% before inflation and 3% inflation. These are editable starting assumptions, not predictions. Allow for investment fees in the return you choose.

Sample market path

Generates one path from your age ranges, target average, limits and down-year settings. Re-forecast generates another sample; Undo can restore the previous one. A sample is not a probability-of-success analysis.

Historical returns

Replays a chronological window of annual S&P 500 total returns, including dividends. It is a U.S. stock benchmark, not a diversified portfolio or a forecast. Your own inflation and tax settings still apply.

Today’s versus future dollars

Future dollars show modeled amounts in each future year. Today’s dollars discount those amounts using your inflation assumption to show purchasing power relative to the plan’s starting year.

4. Add changes that matter to you

Life events can add recurring expenses, one-time withdrawals, incoming lump sums or loan payments. Event ages refer to your timeline. For recurring expenses, both the starting and ending ages are included.

Choose today’s dollars to inflate an amount to its event year, or event-year dollars when you already know the future amount. Incoming lump sums should be net of taxes and transaction costs. One-time events occur at the start of the modeled year. Uninvested lump-sum proceeds are excluded rather than tracked as extra cash.

Loan events model payments and outstanding balances. Property and business values are not automatically added as assets, so the investment projection is not a complete household net-worth statement.

5. Read the result, then compare

The calculator combines modeled earnings, benefits, contributions, investment growth, spending and withdrawals. It identifies the first year spending cannot be funded. Negative displayed balances represent accumulated unmet spending; they do not create an investable negative account or an automatic loan.

Pin a comparison before changing inputs, or compare saved scenarios. Keep the same market path when isolating the impact of a decision. Export Excel for a portable backup; saved browser scenarios do not sync across devices.

Taxes and account limits

The automatic estimate uses the model’s implemented 2026 U.S. federal rules and a user-entered state/local estimate. It simplifies real tax returns. Manual rates are also available. Filing details, credits, deductions, gains, benefit taxation and future laws can make actual taxes different.

Custom early retirement-account access assumes an applicable exception; early-withdrawal penalties are not modeled. Qualified Roth treatment assumes the relevant conditions are met. Contribution eligibility and limits are not fully enforced. Confirm these details independently before relying on a plan.

Useful references: Social Security benefit estimates, IRS retirement-plan information, and the historical market data source. More model notes and sources are in the calculator’s How it works tab.