sandwich money · See what your savings could do

Your assumptions

Live

Change a number. Tap to learn what it means.

Plan your future income

Set your monthly income and timeline. Find how much you need invested today, with no further contributions.

Monthly take-home income needed

Spending money after modeled fees and tax, in today’s buying power when inflation indexing is on.

Start withdrawals in

Your savings remain invested during this time. No income is withdrawn and no new savings are added.

Withdraw income for

Number of years of monthly payments after withdrawals begin. Waiting plus withdrawals can total up to 80 years.

Savings to keep at the end

Target percentage of your starting savings left for the next generation, in today’s buying power.

Die with zero

Your income uses investment returns and the starting savings. We find the starting amount that funds every payment and leaves at least your chosen inheritance in 95% of simulated trials.

Increase income with inflationIncludes inflation while you wait, then increases once a year during withdrawals.

I know what I paid for these investmentsEnter the total purchase cost of the retirement portfolio. Otherwise it equals the calculated savings target.

Investment assumptions

Choose your return model, investment costs and rebalancing. Open Country settings in the header to adjust currency, tax and inflation.

How should your money grow?

Lots of possible futures, not one guess.

Each path picks actual past years in a new order. Bad years stay bad. All your withdrawals, fees, taxes and rebalancing still apply.

Years to sample from

Group historical S&P 500 years

Keep 3, 5 or 10 consecutive historical years together, in their original order. Blocks are sampled with replacement; the final block is shortened to fit your plan.

Historical compound return10.02%/ year

Before costs, inflation and tax. This describes the data; it is not the assumed return or a forecast.

How many possible futures?

Sampling details

Trial-shuffle seed

Same seed = same sampled paths. Change assumptions without changing the dice. New shuffle does not change the generated sample bank.

Annual total returns, including dividends. NYU Stern / Damodaran ↗ · January 2026 snapshot. Pre-1957 years are predecessor history.

Important simplifications: each annual return is spread across 12 model months. Total returns are used; dividends are not separately taxed or added to purchase cost. This is a total-return proxy, not a complete taxable-fund model. No currency movements are simulated.

Investment costs

Yearly management fee

A fund-like fee deducted monthly from savings, using the annual rate ÷ 12.

Buy / sell commission

Paid on each new purchase or sale. Not charged on existing starting investments.

These fees are applied separately to every simulated path, not subtracted from a single average return.

Portfolio rebalancing

Rebalance each year

Sell and reinvest this share of the remaining pot once a year. Default: 15%. Set 0% to switch it off.

Moving money, not spending it.

15% means selling 15 of every 100 still invested, then buying again after tax and two trading commissions. It is not a 15% fee.

Happens at the end of months 12, 24, 36… after normal withdrawals, growth, fees and new savings. These sales are extra to those funding your income.

Rebalancing and withdrawals share one yearly gains allowance. The new purchases update your purchase cost. This estimates taxable turnover in your account, not the performance of a stock/bond allocation or trades already reflected in a fund’s return.

Calculations run on the server

YOUR RETIREMENT TARGET

Starting savings for 95% simulated success