Annuity Payout Calculator

How to use this calculator

Three modes answer three different retirement questions. Choose the tab that matches what you are trying to find out.

Find Payout tab. You know your balance, your expected return, and how many years you need income. The calculator tells you the maximum sustainable periodic withdrawal that will deplete the account to zero exactly at the end of the period.

Find Duration tab. You know your balance, your return, and how much you want to withdraw each period. The calculator tells you how long the money will last before the balance reaches zero.

Find Required Balance tab. You know how much monthly income you need and for how long. The calculator tells you the lump sum you need to have at retirement to fund that income stream.

Inflation adjustment. Enable the toggle to enter an annual inflation rate. The calculator shows both the nominal withdrawal schedule and the real (inflation-adjusted) purchasing power of each year’s withdrawals. The balance depletion chart displays both lines when inflation is enabled.

What this calculator models

This calculator answers the mathematical form of the retirement income question. Given a pool of money earning interest, how much can you draw down periodically before the pool is empty?

The payout formula is the present value formula in reverse. Instead of asking what stream of payments is worth today, you ask: what equal payment can I extract from a given lump sum over a given period at a given interest rate?

This is also the same math used for mortgage payments. The bank has a lump sum (the loan principal); you pay it down in equal installments over a fixed term. The only difference is direction: you are paying down someone else’s balance then, and drawing down your own now.

The practical implication is that the factors controlling how long your money lasts are the same ones that control mortgage payoff: the balance, the interest rate, the payment size, and the number of periods.

The formulas used in each tab

Find Payout (PMT):

PMT = PV x r / [1 - (1 + r)^(-n)]

Where PV is the starting balance, r is the periodic rate (annual rate / payment frequency), and n is total periods (years x frequency).

Find Duration (n):

n = -ln(1 - PV x r / PMT) / ln(1 + r)

This formula requires that PMT > PV x r, meaning the withdrawal must exceed the interest earned each period. If withdrawals are smaller than interest, the balance never depletes.

Find Required Balance (PV):

PV = PMT x [1 - (1 + r)^(-n)] / r

This is the standard present value of an annuity formula. It answers: what lump sum today is equivalent to receiving PMT every period for n periods at rate r?

Withdrawal rate benchmarks

How sustainable is your withdrawal rate? The ratio of annual withdrawal to starting balance is the withdrawal rate, and it has been studied extensively in the context of retirement planning.

Annual Withdrawal Rate	Balance Required for $4,000/mo	Est. Duration at 5% Return	Common Name
3.0%	$1,600,000	50+ years	Ultra-conservative
3.5%	$1,371,429	40+ years	Conservative
4.0%	$1,200,000	~30 years	The 4% rule
5.0%	$960,000	~22 years	Moderate
6.0%	$800,000	~17 years	Aggressive
7.0%	$686,000	~14 years	High risk
8.0%	$600,000	~12 years	Rapid depletion

The 4% rule (originated by financial planner William Bengen in 1994) suggests that a portfolio of stocks and bonds can sustain a 4% initial withdrawal, adjusted annually for inflation, for at least 30 years with high probability. More recent research suggests 3.5% may be more appropriate given lower expected bond returns and current valuations.

How inflation erodes fixed payouts

A fixed nominal payout loses purchasing power every year inflation occurs. At 3% annual inflation, purchasing power halves in approximately 23 years.

Several approaches address this:

Inflation-indexed annuities. Some insurance products offer payments that increase with inflation, but they start lower to compensate for future increases.

Rising withdrawal rates. Plan to withdraw more each year to maintain purchasing power. This depletes the balance faster but maintains real income.

Growth allocation. Keeping a portion of retirement assets in equities that historically outpace inflation helps preserve real value over long retirements.

Delay Social Security. For US retirees, Social Security benefits are inflation-indexed. Delaying benefits to age 70 maximizes the inflation-adjusted guaranteed income floor, reducing dependence on portfolio withdrawals.

Longevity risk and the find-duration result

The hardest part of retirement income planning is not knowing how long you will live. The Find Duration tab shows exactly when your balance reaches zero at a given withdrawal rate. But life does not follow a schedule.

Average life expectancy in the United States for a 65-year-old is approximately 19-21 more years (to age 84-86). But nearly 25% of 65-year-olds today will live past age 90, and roughly 10% past age 95.

If your balance is projected to last 22 years and you live 30, you face a shortfall. Strategies to manage this:

Use a conservative withdrawal rate. At 3.5-4%, most balanced portfolios historically last 30+ years even through poor market sequences. Running the calculator at 3.5% withdrawal versus 5% shows the difference in projected duration clearly.

Purchase guaranteed income. A life annuity from an insurance company that pays until death removes longevity risk entirely at the cost of flexibility and liquidity. This is the insurance product version of an annuity.

Keep a growth allocation. Even in retirement, keeping 30-50% in equities provides growth that can extend portfolio life and outpace inflation, at the cost of increased short-term volatility.

Sequence-of-returns awareness. Poor returns in the first 5-10 years of retirement do disproportionate damage because you are drawing down a large balance before growth can compound. A 40% stock market drop in year 2 of retirement is far more damaging than the same drop in year 15.

Using find-required-balance to set a savings target

The Find Required Balance tab is the most actionable mode for people still in the accumulation phase. It answers: “How much do I need to retire with the income I want?”

Enter your desired monthly income (PMT), expected portfolio return during retirement, and how many years you need the income to last. The result is a concrete savings target.

Pair this with the Annuity Calculator’s Retirement Planning tab to see whether your current savings rate gets you there. The process:

1. Use Find Required Balance to compute target balance (say, $1.1 million for $5,000/month for 25 years at 5%)
2. Switch to the Annuity Calculator, Retirement Planning tab
3. Enter your current age, retirement age, expected return, and current savings rate
4. If the projected balance falls short, increase the PMT (contribution) until the gap closes

This two-calculator workflow models the full savings-to-income lifecycle: how contributions grow during working years and how the resulting balance supports income during retirement.

Common mistakes in withdrawal planning

Using a return rate that is too high. If you assume 8% returns during retirement but the portfolio earns 5%, your balance depletes much faster than projected. Use conservative assumptions in retirement, when there is less time to recover from shortfalls.

Forgetting taxes. Withdrawals from traditional IRAs and 401(k)s are taxed as ordinary income. A $4,000/month gross withdrawal at a 22% marginal rate leaves $3,120/month after federal tax. Factor taxes into your target income before running the calculator.

Treating the plan as static. Life circumstances change. Review and recalculate your withdrawal plan every few years, especially after major market moves. If your balance has grown faster than expected, you may be able to increase withdrawals. If it has fallen, cutting back early preserves the balance much more effectively than waiting.

Not accounting for large irregular expenses. Medical costs, long-term care, home repairs, and travel can create spending spikes that exceed the regular withdrawal amount. Keep a cash buffer outside the annuity calculation for irregular needs.

Overlooking Social Security and other income. The PMT in this calculator is the income needed from your portfolio. If Social Security or a pension covers $2,500/month and you need $5,000/month total, enter $2,500 as the portfolio requirement, not $5,000.

The bottom line

The annuity payout formula does one thing: it translates a starting balance into a sustainable periodic income for a known period. Use it to answer the three core retirement questions — how much can I draw, how long will it last, and what balance do I need — and to model the impact of inflation on real purchasing power over time.

The most actionable output for people still saving is the Required Balance calculation. Work backward from your income target to a concrete savings goal, then use the Annuity Calculator to plan your contribution path to reach it.

For those already in retirement, the Find Duration and Find Payout tabs provide the ongoing sanity check: given what the portfolio has actually earned and what you have actually spent, does the original plan still hold? Rerunning the calculation each year with current values gives you an early warning if spending adjustments are needed before a shortfall becomes unavoidable.

Sequence of returns risk in retirement drawdowns

One factor the simple payout formula does not capture is sequence of returns risk: the outsized damage that early poor returns cause during the withdrawal phase.

When you are accumulating savings, a bad year early simply means more time to recover. When you are withdrawing, a bad year early means selling depreciating assets to fund withdrawals, permanently reducing the shares available to benefit from the eventual recovery.

Research by financial planner Michael Kitces and others shows that the actual 30-year portfolio survival rate depends heavily on what happens in the first ten years. A retiree who experiences a 30% portfolio drop in year 2 and then 7% returns for the next 28 years fares far worse than one who experiences 7% returns for 28 years and then a 30% drop in year 29. The math of the payout formula treats all years equally; the reality of sequence risk does not.

Practical defenses against sequence risk:

Cash buffer strategy — Keep one to two years of expenses in cash or short-term bonds. Draw from this buffer during market downturns instead of selling equities at depressed prices. Replenish the buffer during strong years.

Dynamic withdrawal rate — Reduce withdrawals modestly (by 5-10%) in years when the portfolio falls significantly. Even a small short-term reduction in spending can extend portfolio life meaningfully.

Floor and upside approach — Fund non-discretionary expenses (housing, food, healthcare) from guaranteed sources (Social Security, pension, fixed annuities) and use the investment portfolio only for discretionary spending. This means market volatility affects lifestyle choices but not survival.

Bucket strategy — Divide the portfolio into buckets by time horizon: a near-term bucket (1-5 years) in stable assets, a mid-term bucket (5-15 years) in bonds, and a long-term bucket in equities. Withdrawals come from the near-term bucket, which gets refilled from the mid-term bucket during good years.

The payout calculator shows the steady-state math. Layer sequence risk awareness on top of it to build a plan that accounts for the variability of actual returns.