Published April 2026
How to Stress-Test Your Retirement Plan Until It Breaks
Most people run the Monte Carlo simulation, see a high success rate, and call it a day. Plan's good. Moving on.
That's fine as far as it goes. But it leaves an important question unanswered: how much cushion do you actually have? A 91% success rate and a 99% success rate both feel like "good." They are not the same thing.
There's a simple test that takes about five minutes and tells you a lot more than the headline number. I call it finding your pain point.
What Is a Pain Point?
Your pain point is the monthly expense level at which your retirement plan starts to crack — specifically, where your Monte Carlo success rate drops below 90%.
Why 90%? Because it's a reasonable threshold for "I can sleep at night." Below that, you're in territory where one-in-ten historical market scenarios ends with you running out of money. That's not catastrophic, but it's not comfortable either. Above 90%, you've got a plan with real margin. Below it, you've got a plan that depends on things going reasonably well.
The gap between your actual expenses and your pain point is your true financial cushion. It's more informative than any single success rate number.
How to Find It
The process is straightforward:
Step 1. Enter your real monthly expenses in the calculator and run the Monte Carlo simulation. Note your success rate.
Step 2. Go back to the Expenses tab and start raising your numbers — housing, food, healthcare, whatever makes sense. You're not trying to be realistic here. You're stress-testing.
Step 3. Run the simulation again. Keep pushing expenses higher and re-running until your success rate drops below 90%.
Step 4. The expense level where you cross that threshold is your pain point. The difference between that number and your real expenses is your cushion.
It sounds tedious. It takes maybe five minutes. Do it anyway.
What I Found When I Did It
I'll walk through my own numbers, roughly. My actual monthly expenses in retirement — mortgage, healthcare for two, everything — come in around $10,500 a month. That includes $2,000 a month for medical coverage, which is a real number for early retirees who aren't yet on Medicare.
With those expenses, my Monte Carlo success rate came back at 100%. Which felt great, but also made me suspicious. A 100% success rate means your plan survived every single one of 10,000 historical market scenarios going back to 1928. That includes the Great Depression. That includes the 2008 crash. If you're hitting 100%, you either have a very strong plan, or something is off.
In my case, it turned out to be a little of both. (More on that in a moment.)
I started pushing expenses up. At $12,000 a month, still 100%. At $13,000, still 100%. At $14,000 a month, the success rate finally cracked — dropping to 92%.
My pain point is roughly $13,800 a month. My real expenses are $10,500. That's a cushion of about $3,300 a month — or roughly $40,000 a year of spending margin before my plan starts showing stress.
That's a number I can actually use. It tells me how much healthcare costs can rise before I need to worry. It tells me how much lifestyle inflation I can absorb. It tells me what a bad sequence of market returns actually costs me in spending flexibility.
A Word About 100% Success Rates
If you're seeing 100% and it feels too good to be true, check a few things before you declare victory.
First, make sure the simulation is using the right retirement age. The Monte Carlo tool uses the earliest withdrawal age across all your accounts as the point where accumulation stops. If your earliest withdrawal is from a high-yield savings account at 55, but your brokerage withdrawals don't start until 65, the simulation should be stopping contributions at 55 — not growing your portfolio for another decade it doesn't actually have.
Second, check your return assumptions. If your high-yield savings account is set to a 10% annual return, that's not a savings account anymore — that's a stock market account with a different label. HYS rates are historically much lower. Inflated return assumptions will inflate your success rate.
What the Pain Point Actually Tells You
Once you have your number, a few things become clearer.
It tells you what your real financial risks are. If your cushion is $500 a month, healthcare cost increases are an existential problem. If your cushion is $3,000 a month, healthcare is manageable. You don't need to guess — the math tells you.
It tells you whether your plan is fragile or resilient. A plan that breaks at $11,000 when your real expenses are $10,500 is fragile. A plan that doesn't break until $15,000 when your real expenses are $10,500 is resilient. Both might show a 94% success rate. Only one of them has room to absorb bad surprises.
It also gives you an early warning threshold. If your actual spending ever starts creeping toward your pain point — because of inflation, medical costs, a kid who needs help, whatever — you know it's time to make adjustments. You're not flying blind.
One More Thing Worth Knowing
Run the simulation three times with the same inputs. You'll get slightly different results each time — maybe 91.2%, then 90.8%, then 91.5%. That's not a bug. That's 10,000 random samples of historical market sequences producing natural variation. Small differences between runs mean the simulation is working correctly. If the number swung from 70% to 95% between runs, you'd have a problem. Tight variation means you can trust the number.
The pain point exercise works best when you run each expense level two or three times and take the average. Adds maybe two minutes. Worth it for a decision this important.
The Short Version
Don't stop at your success rate. Find the expense level where your plan breaks. Note the gap between that number and what you actually spend. That gap is what your retirement plan is really worth — not the percentage on the screen.
A plan with a 94% success rate and $4,000 a month of cushion is a better plan than one with a 97% success rate and $400 a month of cushion. The headline number doesn't tell you that. The pain point does.