How to use
- Enter your age, the age you plan to retire, your current savings and your monthly contribution.
- Set an expected return. Try a cautious figure and an optimistic one.
- Optional: raise contributions each year, or add inflation to see the result in today’s money.
- Enter the monthly withdrawal you plan in retirement and the age the money should last to.
How the projection works (formula)
Monthly rate i = (1 + r)^(1/12) − 1
Each month balance = balance × (1 + i) + contribution
Today's money = balance ÷ (1 + inflation)^years
Months it lasts = −ln(1 − B × i ÷ W) ÷ ln(1 + i)
- r is the expected yearly return, so a lump sum grows by exactly r each year.
- Contributions are added at the end of each month.
- B is the balance at retirement and W the monthly withdrawal.
- If the monthly growth (B × i) is at least W, the money never runs out.
Example
You are 35, have $50,000 saved and add $500 a month until 67, at 6% a year:
- Balance at 67: about $882,847.
- You paid in $242,000; growth adds $640,847.
- With 3% inflation, that is about $342,842 in today’s money.
Withdrawing $6,000 a month, the money lasts about 21 years 7 months, until about age 88. To last until 95, withdraw about $5,342 a month instead.
Balance at 67 by contribution and return
Starting at 35 with $50,000 saved:
| Monthly contribution | 4% a year | 6% a year | 8% a year |
|---|---|---|---|
| $250 | $366,932 | $602,758 | $1,004,053 |
| $500 | $558,460 | $882,847 | $1,421,252 |
| $1,000 | $941,517 | $1,443,025 | $2,255,650 |
The return matters as much as the amount you save, which is why it is worth testing a lower rate.
Limits of this estimate
- Returns are assumed to be the same every year. Real returns rise and fall, so treat the result as a rough guide.
- Taxes, fees and pensions are not included. Lower the withdrawal if a pension will cover part of your spending.
- The withdrawal stays fixed. With inflation, the same amount buys less each year.
Why the monthly rate is not simply r ÷ 12
Dividing the yearly return by 12 and compounding monthly gives slightly more than r over a year. We use (1 + r)^(1/12) − 1 instead, so 6% a year means exactly 6% a year.
Other calculators may show slightly higher balances for that reason.
To see how a single amount or regular deposits grow without withdrawals, use the compound interest calculator.