How much you can safely spend depends on your portfolio, your other income, and how closely your plan is monitored. Rather than a fixed 4%, we run your plan through Monte Carlo software that scores its probability of success, set a floor you’re comfortable with, and watch that score over time, adjusting if it slips or climbs.
Key takeaways:
– A “safe” spending amount is a number tied to your plan’s probability of success, not a fixed percentage.
– Monte Carlo software tests your plan against thousands of market scenarios and produces a single probability score.
– We set a floor probability you’re comfortable with, then monitor for slippage below it or room above it.
– Guaranteed income covering your essentials lets you carry more spending flexibility with confidence.
Every retiree wants the same number: how much can I pull from my savings each year without running out. It’s the central question of retirement income, and the honest answer is that a single fixed figure is the wrong way to think about it. A number set once, years ago, can’t know what your portfolio or the markets are doing now. Here’s a better way.
What is a safe withdrawal rate?
A safe withdrawal rate is the amount you can spend each year with a high chance the money lasts through retirement. The best-known benchmark is the 4% rule, which came from research by financial advisor William Bengen and the later Trinity study. Spend 4% of your starting balance in year 1, adjust that dollar amount for inflation each year after, and history suggests a diversified portfolio survives 30 years in most cases.
Treat 4% as a reference point, not a plan. It was built on specific assumptions about time horizon, asset mix, and market history, and small changes to those assumptions move the safe number in either direction. For a full look at why the fixed rule has fallen out of favor, see why the 4% rule is dead.
Why is a fixed withdrawal rate risky?
A fixed withdrawal rate is risky because it ignores what your portfolio is actually doing. When you lock in a dollar amount and raise it every year regardless of the market, you spend the same in a crash as you do in a boom. Pulling a fixed amount from a portfolio that just dropped 25% is how a plan runs dry early.
This is the sequence-of-returns problem that makes the early years of retirement so fragile. A fixed rule does nothing to defend against it, because it never adapts. What protects you is a plan that’s measured and adjusted as conditions change, rather than a number set in stone at retirement.
What is Monte Carlo income monitoring?
Monte Carlo income monitoring tests your specific plan against thousands of possible market futures and reports the odds it succeeds. Instead of assuming a single average return, the software runs your income plan through thousands of randomized scenarios, good markets, bad markets, and everything between, and calculates the share of them in which your money lasts. That share is your probability of success.
The power is that the score reflects your actual plan: your portfolio, your spending, your guaranteed income, and your time horizon, all together. A probability of 90% means your plan held up in 90% of the simulated futures. It turns “am I spending too much?” from a guess into a measured number you can watch and manage.
How does the probability floor work?
The floor is a probability of success you’re comfortable with, and monitoring keeps your plan at or above it. We set that floor with you based on how much certainty you want, then track your score over time as markets move and your spending evolves. The score isn’t static; it drifts as your portfolio and the world change, and that drift is the signal.
We watch it in both directions. If the score slips toward your floor, usually after a rough market stretch or a spending increase, that’s the cue to make a modest adjustment before a small problem becomes a real one. If the score climbs well above your floor, often after strong markets, that’s a sign you may have room to spend more and enjoy it. The floor gives you a clear line, and the monitoring turns spending into an ongoing conversation rather than a
one-time bet.
Fixed rule versus monitored plan
The contrast between a static rule and a monitored plan is the whole point.
| Fixed 4% Rule | Monte Carlo Income Monitoring | |
|---|---|---|
| The Number | Set once at retirement | Scored against thousands of scenarios |
| Personalization | Same rule for everyone | Built on your portfolio and plan |
| Response to Markets | None; keeps rising with inflation | Score moves; you adjust before trouble |
| When Markets Are Strong | You may die with a large surplus | Rising score can signal room to spend more |
| The Experience | Rigid, ignores reality | A floor you hold and monitor over time |
The tradeoff is that your plan requires attention rather than running on autopilot. For most retirees that’s a feature, not a burden, because the alternative is either overspending into a shortfall or underspending out of fear.
How much can you spend, specifically?
Your safe spending number comes from 3 inputs: your guaranteed income, your portfolio, and the probability floor you want to hold. Start by adding up your guaranteed income from Social Security and any pension. Then set a target spending level, run it through the Monte Carlo model, and see the probability of success it produces. Adjust the spending until the score sits at a floor you’re comfortable with.
The result is a spending level with a confidence score attached, not a number pulled from a rule of thumb. From there the job is monitoring: revisit the score as markets and spending change, and adjust when it drifts. This whole process is 1 building block of a complete plan, and it connects directly to your income need and account order, covered in how do you create a retirement income plan.
Frequently Asked Questions
Is 4% still a safe withdrawal rate?
4% remains a reasonable reference point, but it’s rigid and impersonal. A plan monitored against its own probability of success adapts to your portfolio and the markets, rather than locking in a fixed inflation-adjusted amount for 30 years.
What probability of success should I aim for?
There’s no single right number; it depends on how much certainty you want and how much flexibility you have. The idea is to set a floor you’re personally comfortable with, then manage your plan to stay at or above it over time.
What happens if my probability score drops?
A slipping score is an early warning. It usually calls for a modest adjustment, such as trimming discretionary spending for a while, made before a small shortfall becomes a serious one. Catching it early is the whole reason to monitor.
Does guaranteed income change how much I can spend?
Yes. The more of your essentials are covered by Social Security or a pension, the more flexibility you have with portfolio withdrawals, because a bad market year only touches your discretionary spending rather than
your core bills.
The safe-spending question is really about how you want to manage income for the next few decades, and monitoring your plan against a probability floor gives you both confidence and flexibility. If you’d like to see your own probability of success and set a floor, request a meeting and we’ll model it.
About the Author
Kurt Supe, CPA, is a Retirement Planner and Chief Investment Officer for Creative Financial Group. He has spent 30 years helping retirees turn their savings into sustainable, monitored income. Connect on X and YouTube at @KurtSupeCPA, or read more on the CFG team page.