Net Worth Planner

The first row is today. Each row after that is a full year: account balances grow by that year's return, then the year's money in and out is added or taken at year end. Salaries grow at your salary growth rate and stop at retirement age (an end age can only stop them sooner). Everything else you enter in today's dollars (spending, benefits, purchases) rises with inflation, and college costs rise with college cost inflation.

Income is entered before taxes. Each year the planner estimates taxes on pay (federal brackets and standard deduction, Social Security and Medicare, and your state rate), subtracts them along with what you put into retirement accounts, and uses the rest for spending and saving. Contributions to pre-tax accounts lower the tax estimate; Roth contributions don't, because they're made with after-tax money. "Total saving" under Income adds up what goes into retirement accounts from your pay, what your employer adds, and what's left of take-home pay after spending and loan payments. College and big purchases are left out of that figure because they're paid from savings when they happen. The tax rules live in config.js and are simplified: no itemized deductions, credits or local quirks. You can replace the estimate with one overall rate under Assumptions.

Retirement contributions go into retirement accounts while their owner is working. Whatever is left over after spending, debt payments, college and purchases is added to non-retirement savings. When there's a shortfall, it comes out of non-retirement savings first, then pre-tax retirement accounts (taking out enough extra to pay the tax on it), then Roth accounts, which are tax-free. Home and other assets grow but are never sold to cover spending.

Required withdrawals (RMDs). From age 73 (75 if born in 1960 or later), the IRS requires a minimum to come out of pre-tax retirement accounts every year: last year-end's balance divided by a factor from the IRS Uniform Lifetime Table, about 3.8% at 73 and rising with age. The planner takes it each year for each person, taxes it along with that year's other income, uses it for that year's spending first and adds anything left over to non-retirement savings. If one partner's plan ends first, the other takes over their accounts. Roth accounts have no required withdrawals. It's simplified: there's no still-working exception.

Taxes in retirement. Each year, money taken out of pre-tax accounts (RMDs and any other withdrawals) is added to that year's other income and taxed through the federal brackets, plus your state rate. Social Security is taxed on the IRS formula: none of it if your other income is low, up to 85% as it rises. Those IRS thresholds have never been raised for inflation, so over a long plan more of it becomes taxable. People 65 and older get the larger standard deduction, and through 2028 the extra senior deduction (smaller at higher incomes). Withdrawals from Roth accounts and non-retirement savings aren't taxed (capital gains aren't modeled). Enter a Tax on withdrawals under Assumptions to use one flat rate instead.

Loans are paid down month by month: each month interest is added at the yearly rate divided by 12, then the monthly payment is taken off, so payoff dates match a normal amortization schedule. If you give a paid-off year without a payment, the planner calculates the payment that clears the loan that year.

To get best, mid and worst cases, the planner simulates 1,000 market paths every time an input changes. In each path, every year gets a random return drawn around your typical return, spread out by the market ups and downs you set (the same draw applies to retirement and non-retirement accounts, since they're in the same market). For each year it then ranks the 1,000 net worths: the best case is the 90th percentile, the mid case is the median, and the worst case is the 10th percentile. The random numbers use a fixed seed, so the same inputs always give the same answer, which keeps scenario comparisons fair. "Savings last in X% of markets" is the share of the 1,000 paths in which savings never run out.

What changes between best, mid and worst? Only market returns. Inflation, Social Security, pensions, spending and taxes on income follow your assumptions the same way in every simulated market, so the worst case means poor investment years, not high inflation. To see higher inflation, use the Inflation slider in Play with it or change it under Assumptions. Social Security rises with inflation every year, like its cost-of-living raise; pensions and annuities only rise if you tick "Rises with inflation". Up to 85% of Social Security counts for federal tax, depending on your other income; it isn't charged state tax, since most states don't tax it. Taxes on withdrawals do change between cases, because how much you take out depends on markets.

Privacy. Your plan is saved automatically in this browser's storage on this device, and nowhere else. The page carries a security rule that tells the browser to block any attempt to send data over the network, so even the planner itself couldn't upload your numbers if it tried. Use Save a copy to keep a backup file or move your plan to another device.

Work-optional age is the earliest age at which your savings would last the whole plan in at least 85 of 100 simulated markets, if you stopped working then (partners shift by the same number of years, and so does the end of each person's last salary, like a lower-paying job before retiring). Items marked Estimated are starting guesses from quick start; edit them to make them yours. The Social Security guess is very rough (a share of your pay, within set limits), so look up your real estimate at ssa.gov.

"Savings last" means there was always enough in savings and retirement accounts to cover the year. This is a simplified model for planning conversations, not tax or investment advice.