See how many years and months your savings last, with or without inflation-adjusted withdrawals.
Example Result
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The calculated result will appear here after you press Calculate.
Estimates for planning only; not financial, tax or investment advice. See our Disclaimer.
Once you stop contributing and start drawing down savings, the question changes from "how much will I have" to "how long will it last." Enter your retirement savings, the average annual return you expect, and the amount you plan to withdraw in the first year. The calculator runs a month-by-month simulation — the balance earns the monthly equivalent of your return, and one twelfth of the year's withdrawal comes out at the end of each month — and reports how many years and months the money lasts, counting only months it can fully cover. Add an inflation rate and the withdrawal rises every year to keep its buying power, which is how the 4% rule and most safe-withdrawal-rate studies define a withdrawal. Leave it empty for a fixed dollar amount.
Enter your total retirement savings.
Enter your expected average annual return.
Enter the amount you plan to withdraw in the first year.
Optionally enter an inflation rate to raise the withdrawal each year (as the 4% rule assumes), then press Calculate.
By O.E. — Partner, chairman of the board and CEO of a metal products manufacturer for 21 years; the company exports to 45 countries.
Drafted with AI assistance; calculations checked against primary sources and tested with the site's own code. About FlowUtil
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The simulation is monthly, because withdrawals are taken monthly in practice and because counting whole years overstates how long money lasts. Each month the balance first earns one month of return, then one twelfth of the year's withdrawal is taken out: Balance = Balance × (1 + i) − W ÷ 12. The simulation stops when the balance plus that month's return can no longer cover a full withdrawal.
The monthly rate is the compound equivalent of the annual return, i = (1 + r)^(1/12) − 1, not the annual rate divided by 12. A 4% annual return is 0.327374% a month, so that twelve months compound to exactly 4% (4% ÷ 12 would compound to 4.07%).
Withdrawals are monthly and at the end of the month. Only fully funded months count: "18 years 10 months" means 226 full withdrawals were made and the 227th could not be paid in full. With inflation, the monthly withdrawal is multiplied by (1 + inflation) at the start of year 2, 3, 4 … — with $40,000 and 3% inflation the second year's withdrawals are $41,200 ($3,433.33 a month) and the tenth year's $52,190.93.
Without inflation there is a closed-form check: months n = −ln(1 − S × i ÷ (W/12)) ÷ ln(1 + i). For $400,000 at 4% with $30,000 a year, n = 226.997, so 226 full months — the same as the simulation. If S × i ≥ W/12 (the first month's return covers the withdrawal) the money never runs out. The simulation stops at 100 years and reports "100+ years".
| Symbol | Meaning |
|---|---|
| S | Retirement savings at the start |
| r | Expected annual return, nominal (0% or higher) |
| i | Monthly rate = (1 + r)^(1/12) − 1 |
| W | First-year withdrawal in dollars (W ÷ 12 a month) |
| Inflation | Optional yearly increase applied to W from year 2 (0–50%) |
| W ÷ S | Initial withdrawal rate shown in the result |
1Testing the 4% rule: $1,000,000 savings, 5% return, $40,000 in year one (4.00%, $3,333.33 a month), raised 3% a year.
Monthly simulation; final-year withdrawal = 40,000 × 1.03³⁴ = 109,276.21
Savings last 34 years 10 months · Total withdrawn = $2,400,270.57
For a 65-year-old that runs to age 99. Sensitivity: with no inflation increase the savings last 100+ years (the first month's return, $4,074.12, exceeds the withdrawal); with 2% inflation they last 45 years 7 months. Inflation, not the return, decides the result here.
2A fixed withdrawal that is too high: $400,000 at 4%, $30,000 a year (7.50%, $2,500 a month).
Month 1: 400,000 × 1.00327374 − 2,500 = 398,809.50 — the return covers only $1,309.50 of the $2,500
Savings last 18 years 10 months · 226 withdrawals, $565,000.00 in total
Without a cost-of-living increase, the $2,500 a month in year 18 also buys far less than it does in year 1.
3Why months matter: $100,000 in a 0% account, $30,000 a year withdrawn.
100,000 ÷ 2,500 = 40 monthly withdrawals
Savings last 3 years 4 months
A year-by-year calculation would report "about 4 years", overstating the duration by eight months.
4Close to sustainable: $800,000 at 5%, fixed $40,000 (5.00%).
First month's return 800,000 × 0.407412% = 3,259.30, below the $3,333.33 withdrawal
Savings last 78 years
5% of $800,000 looks like exactly $40,000, but the return is earned on a balance that shrinks during the year, so the money erodes very slowly. At $39,000 a year it lasts 100+ years.
The 4% rule: in 1994 William Bengen tested historical US stock and bond returns and found that a first-year withdrawal of 4%, raised each year for inflation, had never exhausted a 50–75% stock portfolio in less than 33 years. The Trinity study (Cooley, Hubbard and Walz, 1998) found that inflation-adjusted withdrawal rates of 3–4% produced high success rates over 30 years for portfolios at least half in stocks. Both used real historical return sequences; this calculator uses one constant return, so treat it as an average-case check, not a success probability.
Initial withdrawal rate: below about 4% with inflation adjustment is the conventional safe zone for a 30-year retirement; 5–6% needs a shorter horizon or a higher return than most balanced portfolios have delivered after inflation; above 7% the money runs out in roughly 15–20 years even at a 4–5% return.
What keeps a plan alive is the gap between the return and inflation. In Example 1, 5% return with 3% inflation is a real return of about 1.9%; raise the return to 6% and the plan lasts 45 years 7 months.
Sequence-of-returns risk: two retirees with the same 5% average return can end up very differently if one suffers losses in the first years while withdrawing. A constant-return simulation cannot show this; common safeguards are a lower initial rate, a cash buffer of one to two years of spending, or skipping the inflation increase after a losing year.
Longevity: the CFPB suggests planning for 20 or more years in retirement and notes that, on average, a 65-year-old woman today lives to about 87 and a man to about 84 — and half live longer than average.