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Retirement withdrawal calculator

Simulate thousands of possible market paths to see how likely your withdrawals are to last, and how wide the range of outcomes is. Everything runs on your device.

By the Calcist team · Checked against known answers · Updated October 27, 2026

Private: calculated on your device. Nothing you type is sent anywhere.

Next: Prefer a steady, simple projection? How long will my money last? uses one fixed return. Need to know your required minimum? Try the RMD calculator.

How it works

Each simulation starts with your balance. At the start of each year it takes your withdrawal, then applies a random yearly return and removes inflation, so every figure stays in today's dollars:

Bnext = (B − withdrawal) × (1 + return this year) ÷ (1 + inflation)

The run "lasts" if every withdrawal is paid in full. After all the runs, Calcist sorts the balances for each year and reads off the 10th, 50th (median) and 90th percentiles.

Return models. The lognormal model draws ln(1 + return) from a normal distribution, with its settings chosen so the average yearly return and its standard deviation match what you enter. Returns can't fall below −100%. The normal model draws the return itself from a bell curve and caps losses at −100%. Returns are independent from year to year.

Reproducible. The random numbers come from a seeded generator (Mulberry32 with Box–Muller), so the same inputs and seed always give the same answer. "Re-run" just adds 1 to the seed, letting you see how much the result moves between batches.

Sequence-of-returns risk

Two retirees can earn the same average return and end up in very different places. If the bad years come first, you're selling investments while prices are low to fund withdrawals, and that money isn't there when markets recover. The same bad years late in retirement do far less harm, because the balance has already done most of its work. That's why the spread between the 10th and 90th percentile lines grows so wide, and why a fixed average return can't show this risk.

Checks you can do by hand

Set volatility to 0 and every run is identical. $1,000,000, $40,000 a year at 5% for 30 years with no inflation ends at 1,000,000 × 1.05³⁰ − 40,000 × 1.05 × (1.05³⁰ − 1) ÷ 0.05 = $1,531,511. At a 0% return the same withdrawal runs out in year 26, and a $0 withdrawal always lasts.

Limitations

  • Real markets have streaks, crashes and recoveries that independent draws don't capture, and the future may differ from any assumption you enter.
  • Inflation is fixed, and there are no taxes or fees. Enter a return after fees.
  • Real retirees adjust: they cut spending after bad years, or collect Social Security. A fixed withdrawal is the strictest test.

A planning estimate, not financial, tax or investment advice. Every assumption is listed under the result.

Sources

How we checked this

Before every update, this calculator is run in a real browser with these known answers, and it must match all of them:

  • Volatility 0: $1M, $40,000 a year, 5% for 30 years ends at exactly $1,531,511 ✓
  • Volatility 0 with 2% inflation: $445,593 in today's dollars ✓
  • 0% return: $1M at $40,000 a year runs out in year 26 ✓
  • Withdrawing $0 always lasts, even with 15% volatility ✓
  • 4% of the balance, volatility 0, 5% return, 2% inflation: $701,150 after 30 years ✓
  • Percent mode footnote describes percent-of-balance withdrawals ✓
  • 100% of the balance is refused ✓
  • 1 year, $0 withdrawal: singular year ✓

Last checked October 26, 2026. Spotted something wrong? The math is done in your browser with the formula shown on this page, so you can check any result by hand.

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Questions people ask

What is a Monte Carlo retirement simulation?

It runs your plan through thousands of randomly generated market paths with the same average return and volatility, and counts how often the money lasts. It shows a range of outcomes instead of one straight line.

What is a good success rate?

There's no single right number. A plan that never fails in simulation usually means spending less than you could, and real people can cut back if markets go badly, so a rate below 100% can still be a workable plan if you're willing to adjust.

What volatility should I use?

Volatility is the standard deviation of yearly returns. Broad US stocks have historically swung by roughly 15% to 20% a year; a balanced stock and bond mix swings less. Use a number that matches your mix.

Why do results change when I re-run?

Each seed gives a different set of random market paths. With 5,000 runs, the success rate usually moves by only a point or so between seeds, which shows the sampling error.

Is a percent-of-balance withdrawal safer?

It can never fully run out, because you always take a share of what's left. The trade-off is that your income falls after bad years, sometimes by a lot.

Related calculators

How long will my money last?See how many years your savings last with regular withdrawals.How much do I need to retire?Your target nest egg from spending, other income and a withdrawal rate, and whether you're on track.RMD calculatorRequired minimum distribution from the IRS Uniform Lifetime Table.FIRE calculatorYour FIRE number and years to financial independence from your savings rate.