Retirement Duration Calculator
Estimate how many years your nest egg may last based on your spending, expected investment return, inflation, and outside retirement income.
Assumption: withdrawals begin now and increase monthly with inflation.
What this calculator helps you answer
The biggest retirement question is simple: Will my money last? This calculator estimates how long your retirement savings can support your lifestyle after accounting for:
- Your starting investment balance
- Your desired annual spending
- Guaranteed income such as Social Security or pension
- Expected portfolio return
- Inflation over time
It gives you a practical estimate of your retirement runway, plus a year-by-year snapshot so you can see how balances and withdrawals evolve.
How the retirement savings calculation works
1) Net withdrawal need
First, the tool calculates how much you need from your portfolio each year:
Net annual withdrawal = Annual spending − Other annual income
If your outside income covers all spending, your investments may continue growing (depending on return assumptions).
2) Monthly simulation
Instead of using one large yearly step, the calculator uses monthly compounding for better realism:
- Portfolio balance grows by your expected monthly return
- A monthly withdrawal is deducted
- The withdrawal amount increases each month with inflation
This process repeats until the balance is depleted, or until a long horizon is reached.
3) Final estimate
The output includes:
- Estimated years and months your savings may last
- Approximate age when depletion could happen
- Total amount withdrawn over the simulation
- A projection table for quick planning review
How to use this tool effectively
Use realistic assumptions. It is tempting to overestimate returns and underestimate inflation, but conservative inputs usually lead to better planning decisions.
- Try multiple return scenarios (optimistic, baseline, conservative)
- Test spending reductions of 5% to 15%
- Increase outside income assumptions if you plan delayed Social Security
- Revisit your estimate yearly as markets and life plans change
Example scenario
Suppose you have $850,000 saved, spend $60,000 per year, receive $24,000 from Social Security, expect 5.5% returns, and plan for 2.5% inflation. Your net draw from investments is $36,000 in year one, and that amount increases over time due to inflation.
Depending on returns and inflation outcomes, the plan might last decades or run short earlier than expected. The point of this calculator is to help you spot risk now, when you can still adjust your plan.
Ways to make your money last longer
Reduce withdrawals slightly
Even small spending cuts can add years to portfolio longevity. A few hundred dollars less per month can materially improve outcomes.
Delay benefits if possible
For some retirees, delaying Social Security increases guaranteed lifetime income, reducing pressure on investments later.
Stay flexible in down markets
Large withdrawals during bear markets can damage long-term sustainability. Having a flexible spending rule can help reduce sequence-of-returns risk.
Keep an emergency cash buffer
A reserve of cash or short-term bonds can reduce the need to sell equities at bad times.
Important limitations
This is an educational estimator, not a guarantee. Real life includes taxes, changing spending needs, healthcare costs, long-term care events, and unpredictable market sequences.
Use this as a planning starting point, then validate your strategy with a fiduciary financial planner if you need personalized guidance.