Savings
How Long Will My Money Last?
Everyone asking "can I retire on this" is really asking how long a pile of money survives being spent. The honest answer needs both growth and inflation in the same simulation — money that grows at 5% while the life it pays for inflates at 3% behaves nothing like the back-of-envelope division suggests. This tool runs that simulation to the last dollar.
Results
Your money lasts: 20 years 10 months, Monthly withdrawal (today): $2,500.00, Final monthly withdrawal: $4,515.26, Total withdrawn: $851,262.80
- Your money lasts
- 20 years 10 months
- Short of your 30-year horizon by 9 years 2 months
- Monthly withdrawal (today)
- $2,500.00
- What it buys now, before inflation
- Final monthly withdrawal
- $4,515.26
- Same purchasing power, in the final year’s dollars
- Total withdrawn
- $851,262.80
- Everything the balance paid out over its life
Year by year
| Years in | Monthly withdrawal | Balance |
|---|---|---|
| Today | $2,500.00 | $500,000.00 |
| 5 | $2,898.18 | $461,684.02 |
| 10 | $3,359.79 | $383,842.56 |
| 15 | $3,894.91 | $250,709.26 |
| 20 | $4,515.26 | $41,323.77 |
| 21 | $4,515.26 | $0.00 |
- The withdrawal escalates every year by the inflation you entered, so the dollar column of this table is what keeps buying the same life — flat withdrawals would look safer and quietly lose a third of their purchasing power per decade.
- You are drawing 6% of the balance per year at the start: the classic 4%-rule guideline says roughly 4% of a diversified portfolio has historically lasted about 30 years — above it, the horizon shortens fast.
- The return is a planning assumption, not a promise — sequence matters in real life, and early bad years cut deeper than late ones. See the financial disclaimer before betting a retirement on one rate.
- The plan falls 9 years 2 months short of your 30-year horizon: either the withdrawal comes down, the balance grows before it starts, or the plan changes — the savings-rate calculator sizes the catch-up.
How to use this calculator
- Enter the balance you would live on: retirement accounts, savings, everything withdrawable.
- Enter the monthly spending it must cover — today’s number; the tool inflates it automatically.
- Enter the average annual return you expect on the balance while it is being spent, and the inflation you expect on your spending.
- Read how long the money lasts, the trajectory table, and how much the final year’s withdrawal has grown to in nominal dollars.
How the calculation works
each month: balance = balance × (1 + r ÷ 12) − withdrawal each year: withdrawal = withdrawal × (1 + inflation) result: the month the balance first reaches zero
A monthly simulation with annual inflation steps — the same structure lenders use for amortization, run backwards. Growth compounds monthly on the remaining balance while the withdrawal escalates once a year to hold its purchasing power; the horizon is the first month the balance can no longer cover the payment.
Worked example
Input
Savings: $500,000. Monthly withdrawal: $2,500 today. Average return: 5%. Spending inflation: 3%.
Result
The money lasts 20 years and 10 months (250 months). By the final year the same lifestyle costs $4,515.26 a month, and the account pays out $851,262.80 in total — $351k of it grown, the rest the original balance. Without the inflation step, the same inputs would look like 35 years 11 months: inflation quietly takes 15 years off.
Assumptions and important notes
- A single average return compounds monthly; real portfolios swing year to year, and early losses deplete faster than this average suggests (sequence-of-returns risk).
- The withdrawal escalates annually by the inflation entered — holding purchasing power, which is what an actual retirement budget demands.
- No taxes on withdrawals are modeled: traditional accounts owe income tax on every dollar out, Roth dollars come out free — the effective withdrawal for a traditional account is higher than it looks.
- Returns are nominal planning assumptions, not forecasts — see the financial disclaimer.
Frequently asked questions
How is this different from the FIRE calculator?
They are inverses. The FIRE calculator starts from your spending and solves for the portfolio that sustains it indefinitely; this one starts from a portfolio you have and finds the date it runs dry. If this tool says your money outlasts 100 years, you have passed your FIRE number — the two tools meet at the same boundary from opposite sides.
Why does inflation matter so much?
Because the withdrawal has to grow every year just to buy the same things, while the balance is shrinking. At 3% inflation the year-20 withdrawal is about 1.8× today’s — a $2,500 lifestyle becomes $4,515 a month. Skipping the inflation step is the single most common error in retirement napkin math; the worked example shows it adding 15 imaginary years.
What return should I enter?
A conservative long-run portfolio assumption is in the 4–6% nominal range for a diversified stock/bond mix; cash-like assets earn less but carry less sequence risk. Since withdrawals mean you are selling in down years too, temper optimism: the difference between 7% and 5% here is decades of runway.
What withdrawal rate is safe?
The classic guideline is about 4% of the starting balance per year, from historical U.S. portfolio studies (the Trinity study) — roughly $1,650 a month per $500,000. Higher initial rates shorten the horizon quickly: the 6% this page opens at buys 20 years, not 30+. Historical patterns are not a guarantee; see the financial disclaimer.
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