Annuity Payout Calculator: Turning a Lump Sum Into Monthly Income
Sooner or later, a pile of money has to become a paycheck: a retirement account, a settlement, an inheritance, the proceeds from selling a business. The question is the same: if I have this much money, how much can I take out each month, and for how long? This annuity payout calculator answers that. Give it a lump sum and an expected return, and it turns that pot into a monthly income, or, flipped the other way, tells you how long a withdrawal you pick will last.
The part people underestimate is that the pot doesn't just sit there shrinking. While you draw from it, whatever is left keeps earning.
The two directions of the calculator
You can run this calculator in either direction, and the first starts with a time horizon: you say you want the money to last 25 years, and it tells you the monthly payment that pot supports over exactly that period, the version most people use for retirement planning. The second starts with a monthly amount instead: you say you need $2,500 a month, and it works out how long your pot lasts at that rate. Sometimes the answer is "longer than you'll need." Other times it's "about eighteen years," and then you know, right now, while you can still do something about it, that the amount has to come down or the pot has to grow. Better to learn that from a calculator than from an empty account at eighty.
Every input, explained
- Money available (the lump sum): the pot you're starting with: a retirement balance, a settlement, any sum you plan to draw down.
- Expected annual return: the yearly growth rate you assume the remaining pot earns. This is the input that matters most, and the one people are most tempted to flatter. Five percent is a common planning assumption. It's not a promise.
- Years (payout period): how long you want the money to last, in the plan-by-years direction. Longer period, smaller payment, though the return softens that trade-off.
- Monthly payout (withdrawal): the amount you want each month, in the plan-by-payout direction. The calculator turns this into a lifespan for the pot.
- Payment frequency: most payouts are monthly, which is what this calculator assumes. Quarterly or annual income should be converted to a monthly figure first.
- Timing: whether each payment comes at the end of each month (the usual setup, used in every number below) or at the beginning. Beginning-of-month payments are slightly more generous, because each payment skips a month of earning.
A worked example: $500,000 over 25 years
Work through one full example. A retiree has $500,000, expects a 5% annual return, and wants the money to last 25 years.
- Monthly rate: 5% ÷ 12 = 0.4167% per month, a small rate that matters a lot over 300 months.
- Count the payments: 25 years × 12 = 300 monthly payments.
- Apply the payout formula: monthly payment = lump sum × monthly rate ÷ (1 − (1 + monthly rate)−300). Feed in $500,000 and 0.4167% and you get $2,922.95 per month.
- Sanity-check it: simple division gives $500,000 ÷ 300 = $1,666.67 a month; the real answer is $1,256 higher every month, because the pot keeps earning while you draw it down.
- Flip it around: if our retiree only needs $2,500 a month, the same $500,000 at 5% lasts 431 months, about 35.9 years. That is nearly eleven years longer than the 25-year plan, for a payment about $423 a month smaller.
- Check what the $2,500 plan actually needs: funding exactly $2,500 a month for exactly 25 years at 5% takes $427,650.12. Our retiree has about $72,350 more than that, which buys either a higher payment ($2,922.95) or more years (35.9), not both.
The number behind the number: the formula assumes a smooth return, the same 5% every year, no crashes, no flat years. Real markets don't behave like that, and a bad few years right at the start, when the pot is biggest, hurts most. Stress-test it before you trust it with your life.
How stretching the years changes the payment
The same $500,000 at 5% pays out like this over four horizons, and the payment falls gently as the years stretch, because the return keeps cushioning the longer plans.
| Payout period | Monthly payments | Monthly payout | Total paid out |
|---|---|---|---|
| 15 years | 180 | $3,953.97 | $711,714.60 |
| 20 years | 240 | $3,299.78 | $791,947.20 |
| 25 years | 300 | $2,922.95 | $876,885.00 |
| 30 years | 360 | $2,684.11 | $966,279.60 |
Two things jump out. Doubling the horizon from 15 to 30 years only cuts the payment by about a third, from $3,953.97 to $2,684.11. And the total paid out grows with the horizon: $711,714.60 over 15 years versus $966,279.60 over 30 years, all from the same $500,000 pot.
The "never runs out" line
There's a threshold hiding in these numbers. If you withdraw only the interest the pot earns, the pot never shrinks. At 5% on $500,000, the pot earns $25,000 a year ($2,083.33 a month), and if you withdraw that or less, the principal stays whole forever, in nominal terms. Withdraw more, and the pot slowly drains.
Our $2,500 withdrawal sits above that line, $416.67 a month more than the pot earns, which is why it has a limit at all: after 431 months, it's gone. That limit is the plan working as designed. But know which side of the line you're on. Below it, your worry is inflation, not exhaustion. Above it, your worry is the calendar: does the pot outlive you? Don't romanticize the line itself. A pot that never shrinks in nominal terms still shrinks in real terms if prices rise.
Common mistakes
- Assuming the return is guaranteed. Five percent is an assumption, not a contract. If the real return averages 3% instead, that $2,922.95 payment drops sharply, and a plan built on 5% runs short years early.
- Ignoring inflation. A fixed $2,922.95 a month sounds comfortable today. In 25 years, at even modest inflation, it buys far less, possibly barely half what it buys now. No inflation adjustment means a pay cut every single year.
- Forgetting tax and fees. The calculator's numbers are pre-tax and pre-fee. Withdrawals from a traditional retirement account are usually taxed as income, and fund fees nibble at the return every year, so a $2,922.95 gross payment might land closer to $2,300 after tax.
- Spending the pot's growth in the early years. The early years are when the pot is largest and its earnings do the most work. Raiding it for a big expense in year two costs you decades of growth on that amount, not just the amount itself. The most expensive withdrawals are the early ones.
- Setting the plan once and never revisiting it. Markets move, health changes, costs shift. A payout plan drawn up at sixty-five and never touched again slowly goes stale.
Practical tips
- Stress-test at 3%. Run the calculator again with a lower return and see what payment that supports. If your lifestyle only works at 5% or better, your plan is fragile. Build the budget around the lower number.
- Keep a cash buffer. Hold one to two years of withdrawals in cash, separate from the invested pot. When markets fall, draw from the buffer instead of selling investments at depressed prices.
- Re-run the numbers yearly. Once a year, plug in your real balance and the years you still need to cover. Adjust early, while a small trim still fixes it.
Frequently asked questions
How much monthly income will $500,000 give me?
It depends on the return and the horizon. At 5% a year, $500,000 pays $3,953.97 a month over 15 years, $2,922.95 over 25 years, and $2,684.11 over 30 years. Shorter horizon, bigger payment, but the pot empties sooner.
How long will $500,000 last if I withdraw $2,500 a month?
At 5% a year, about 431 months, roughly 35.9 years. That's far longer than the 200 months simple division would suggest, because the pot keeps earning while you draw from it.
What withdrawal rate never runs out?
Any withdrawal at or below the pot's earnings. On $500,000 at 5%, that's $2,083.33 a month. At that rate the principal never shrinks in nominal terms, so the income can continue indefinitely. The catch is inflation: a payment that never rises buys less every year.
Is the 5% return guaranteed?
No. It's a planning assumption, and real returns vary year to year, sometimes sharply. A guaranteed annuity from an insurer is a different product: it trades a lump sum for promised payments, and the insurer bears the market risk.
Should I take monthly payments or a lump sum?
Monthly payments protect you from yourself: they turn a pot into a paycheck and make it hard to spend decades of income in a single year. A lump sum gives you control, but also the full responsibility of making it last. Most people sleep better with a monthly plan, plus a cash buffer for big expenses.
Related calculators: Annuity Calculator, Bond Calculator and Finance Calculator.
What a pot pays out depends on the years it had to grow. The growth side of the story is on the CalcMega Blog.
This guide is general information, not financial advice. Returns are assumed, not guaranteed; taxes, fees and inflation will change your real outcome. Talk to a qualified financial adviser before making retirement decisions.
Investor.gov, run by the US Securities and Exchange Commission, keeps a plain-language section on annuities and payout choices.