How Afterwork Plan works

You enter your numbers once. Afterwork Plan replays them, year by year, through every stretch of US market history since 1928 and reports the earliest month your plan pays what you need in every one of them. This page lists every step and every assumption.

The market history

Yearly returns for the S&P 500 with dividends reinvested, 10-year US Treasury bonds and 3-month Treasury bills, plus US inflation (CPI), for 1928 through 2025. The figures come from Professor Aswath Damodaran's historical returns data at NYU Stern. Stocks and bonds use your own mix, rebalanced every year. Cash earns the Treasury bill rate.

Every amount is adjusted for inflation, so a dollar in your results buys what a dollar buys now.

Every stretch of history

A stretch runs from your age today to the age your plan ends (95 unless you change it). If you're 55, that's 40 years, and there are 59 full 40-year stretches between 1928 and 2025: one starting in 1928, one in 1929, and so on. Your saving years run through the same history as your retirement, so a plan that stops working in five years meets those five years of markets first.

Your plan holds if it pays everything you need, every year, in every stretch. A shortfall under 0.1% of a year's spending is treated as rounding.

Your answer

• Earliest month you can stop. The planner tries stop dates month by month and finds the first one that holds in every stretch.
• Most it pays each month. The highest after-tax monthly spending, to the nearest $10, that holds in every stretch at the stop date you chose.
• The typical and the worst stretch. The typical stretch is the one whose ending savings sit in the middle of all of them. The worst is the one where your paycheck dips lowest.
• Stopping right before a crash. Your stop date is placed right before 1929, 1966, 1973, 2000 and 2008. When a stretch needs years before 1928 or after 2025, those years use long-run averages, and the result says so.

The trim rule

If you turn it on, spending drops by the share you choose (10% by default) in any year your savings are below where they stood on the day you stopped by more than the amount you choose (20% by default). Spending returns to normal as soon as savings recover. Your answer shows the result with the rule, and a second line shows it with no trimming at all.

Taxes

• Federal income tax uses 2026 law: brackets and standard deduction, the extra deduction at 65, the senior deduction for 2025 through 2028, tax on Social Security benefits, and capital gains tax on the gains in brokerage withdrawals.
• Required minimum distributions start at 73 if you were born before 1960 and at 75 if you were born in 1960 or later, using the IRS Uniform Lifetime Table. A required withdrawal you don't need to spend is reinvested in your brokerage account.
• Pre-tax money taken out before 59½ pays the 10% penalty.
• State tax is one flat rate that you enter, applied to taxable income.
• Every withdrawal is grossed up so the full amount you need is left after tax.

Where the money comes from

Each year, income you entered (Social Security, pensions, rental income, part-time work and the rest) is used first. The rest comes out of cash, then the brokerage account, then pre-tax accounts, then Roth accounts. Savings while you're still working go to the account you choose.

Spending can change at ages you choose, and one-time costs (a roof, a car) come out of savings in the year they happen; the trim rule never trims those. Money coming in once, like a home sale or an inheritance, is added to your brokerage account that year. A spouse's pay counts as income until the age they stop working, taxed as ordinary income.

Social Security, pensions and other income

Social Security keeps its buying power every year. So does any income you mark as rising with inflation. A pension or income without cost-of-living raises shrinks with the actual inflation of each stretch. If you don't know your Social Security amount, the estimator uses the 2026 benefit formula (bend points of $1,286 and $7,749, a full retirement age of 67, smaller checks for claiming early and 8% more for each year you wait, up to 70). Your statement at ssa.gov/myaccount is more accurate.

Health insurance before 65

You enter a monthly cost for the years between stopping work and Medicare, or estimate it. The estimate is the 2026 national average benchmark silver marketplace premium for a 40-year-old ($625 a month, from KFF), scaled to your age with the federal default age curve, before any premium tax credit.

What it simplifies

• Your salary while you're still working isn't modeled, so tax on anything you do with pre-tax money in those years is understated.
• Roth accounts are treated as fully available; the five-year and early-withdrawal rules aren't modeled.
• State tax is a single flat rate.
• Investment fees aren't subtracted.
• Payroll taxes on a working spouse's pay aren't modeled.
• Medicare premiums after 65 are assumed to be part of your monthly spending.
• History is a guide, and future markets can be worse than any stretch since 1928.

Your data

The calculations run on your device. Your answers stay in your browser unless you create an account to save them, and they're never shared or sold. The privacy policy has the details.

Afterwork Plan is educational software. It is not a registered investment adviser, broker-dealer or insurance agent, and nothing here is a recommendation to buy or sell any security or to hold any mix of investments.