Odds of success (Monte Carlo)

What it does

Your main forecast assumes a single, steady rate of return every year. But markets don't hand you the same return each year — some years are up 20%, some are down 15%, and the *order* they arrive in matters. Odds of success (a technique called Monte Carlo) faces that head-on.

It runs about 500 separate projections of your plan. In each one, the app rolls fresh, random investment returns year by year — clustered around the return you expect, but with realistic ups and downs. Then it counts how many of those 500 runs your money lasted the whole plan.

• "Success" means one thing: your money never runs out before the end of

your plan.

• The percentage is simply the share of runs that succeeded. 500 runs, 425 of

them never ran out → about 85%.

Cash-like savings barely move in these simulations; investment accounts get the full swing. You'll find this under Stress-test your plan → Odds of success on the Forecast tab. It's a premium feature.

Why it captures "sequence-of-returns" risk

Two retirees can earn the *same average return* over 30 years and end up in very different places — because the one who hit a bad stretch early, while withdrawing, sold investments at low prices and never fully recovered. That's sequence-of-returns risk (defined in the glossary), and a single steady projection can't show it. Running hundreds of randomized orderings does.

What a low or 0% result means

This is the most important part to understand.

A 0% result almost never means "the simulation is broken." It means your plan already runs out of money in the normal, steady projection — so essentially every randomized run also runs out. When you're spending far more than your income plus savings can support, *no amount of good luck in the market rescues it*. Better returns help a plan that's close; they can't close a large, permanent gap.

An honest example. Say your income is $3,400/month, you spend $7,000/month, and you have modest savings. That's a $3,600/month shortfall drawn from savings every month. The savings drain quickly, the plan runs out, and so the odds of success come back at roughly 0%. Running more simulations won't change that — the math is the same in every run.

The fix is the plan, not more simulations. To move a 0% (or very low) result, you change the underlying numbers:

• Bring in more income — delay Social Security for a bigger check, work a

little longer, add a pension or annuity.

• Spend less — trim expenses, or check your real spending on the

Budget tab in case the plan is overstated.

• Both — even small moves on each side add up.

After a change, run the odds again and watch the percentage climb.

How to read the number

There's no official "passing" score, and this is an estimate, not advice. As a rough guide, many planners treat a high probability (say 85–95%+) as comfortable, a middling one as worth shoring up, and a low one as a signal to revisit income or spending. Use it to compare before and after a change — that's where it's most useful.

Next: try the what-if levers to see which single changes move the needle most.