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ReallyEasyTools.com Monte Carlo Retirement Calculator

Will your money last? Run 10,000 simulations of your plan using real S&P 500 history. Free, private, and no sign-up. Read our guides or browse common scenarios.

Profile: Default

Your Financial Details

Current Status
Retirement Plan

Future Assumptions
Simulation Settings

Projected Savings at Retirement

$0

Est. Monthly Retirement Income

$0

Savings Depleted Age

Never

Success Rate (Age 95)

0%

Show Year-by-Year Breakdown
Age Savings Fixed Market Market % Social Sec. Tax Expense Expense % End Balance

How this retirement calculator works

  1. Enter your numbers. Your age, savings, income, savings rate, retirement age, spending and Social Security estimate.
  2. We simulate 10,000 futures. Each one replays S&P 500 annual returns from 1955 to 2024 in a random order, so you see good decades, bad decades and everything in between.
  3. Get your success rate. The share of simulations where your money lasts to age 95, plus your median, best and worst paths year by year.

Why use a Monte Carlo retirement calculator?

Popular retirement scenarios

See all 40 scenarios by age and savings →

Frequently asked questions

What is a good success rate for a retirement plan?

Most planners aim for a success rate of 80% to 90% or higher. A 100% success rate often means you are underspending. The rest of the gap is covered by staying flexible: trimming spending a little after a bad market year makes a big difference.

How does this Monte Carlo retirement calculator work?

It runs your plan 10,000 times. Each run draws S&P 500 annual returns from 1955 to 2024 in a random order and applies them to the stock portion of your savings, while the rest earns your fixed return. The success rate is the share of runs where your money lasts to age 95.

What is the 4% rule?

The 4% rule says you can withdraw 4% of your savings in your first year of retirement, then raise that amount with inflation each year, and your money should last about 30 years. Enter 4% of your projected savings as your withdrawals to see how the rule holds up for your own timeline.

What is sequence of returns risk?

It is the risk that a market crash arrives early in retirement, while you are withdrawing money from a shrinking portfolio. Two retirees with the same average return can end up with very different results depending on the order of those returns. Monte Carlo simulation shows this risk; a fixed-return calculator hides it.

How does inflation affect my retirement?

Your spending and Social Security benefits grow with the inflation rate you set, so a dollar figure decades away buys less than it does today. The calculator shows the present value of your withdrawals and benefits so you can compare them in today's dollars.

What should I enter for Social Security?

Use the estimate from your my Social Security account at ssa.gov for the age you plan to claim. The calculator treats it as the yearly amount when benefits start and raises it with inflation after that.

Is my financial data private?

Yes. All calculations run in your browser, and the numbers you enter are never sent to our servers. Your profiles are saved only in your browser's local storage.

Can I save or share my retirement plan?

Create profiles to save different plans in your browser, and use Share this scenario to copy a link that opens the calculator with your exact inputs.

Retirement planning guides