How a retirement date becomes an odds range.
We do not forecast one clean line. We build thousands of plausible futures and run your plan through every one of them. Each future has its own markets, its own inflation, and your spending year by year. Then we count how often the money still lasts.
You give us the real numbers
Your balances, your accounts, your spending, your planned moves. Nothing is assumed about you that you did not enter. You can change any of it and watch the plan respond.
We model 10,000 different futures
Each future is one plausible run of market returns and inflation. We draw them to match how markets have actually behaved over long histories. That means good years, bad years, and unlucky runs of bad years in a row.
10,000 paths ยท returns, inflation, and bad years coming firstWe run your whole life through each one
In every future, we apply your spending, your taxes, your withdrawal strategy, and your life events. We do it year by year, from today to your life expectancy. Each future ends with a balance: enough, or not enough.
We count, and we tell you plainly
If your money lasts in 9,200 of the 10,000 futures, your success rate is 92 percent. We do not hide that behind one rosy average. We show you the whole spread, including the futures where things go wrong.
Every dial is yours to turn.
A model is only as honest as its assumptions and we don't bury them. Each assumption is visible, editable, and explained where you set it.
Expected returns
Pick a conservative, historical, or custom return model. The default leans cautious on purpose.
Inflation
Set the long-run inflation rate, or let it vary across the simulated futures alongside returns.
Life expectancy
Plan to a specific age. Planning longer is more conservative, and we recommend it.
Spending and one-offs
Base spending plus large financial changes: a home sale, a college bill, a new roof, a windfall.
Withdrawal strategy
Fixed, guardrails, or bucket. Each changes how you draw down, and how taxes land.
Asset mix and taxes
Your stock and bond split, account types, and the tax rules that apply to each.
How Glidepath generates the market paths.
We run three return-generation modes and let you see how they compare. Each has different strengths and different blind spots.
Random futures (Monte Carlo): 10,000 paths
Monte Carlo is the name for building many random futures instead of one forecast. We base the assumptions on historical market data, then run 10,000 different scenarios. Each one plays out differently, so you can see how much timing matters. It is not just whether markets go up or down, but when the ups and downs happen.
History replay, back to 1872
We replay every rolling retirement window in the historical record, back to 1872. This includes the Great Depression, 1970s stagflation, and every other bad stretch markets have actually lived through.
Real-world pattern mixing
We take multi-year chunks from actual history and shuffle them in new combinations. This preserves the real market patterns people have actually experienced, while creating new scenarios that could happen but haven't yet.
What the three lines actually mean.
Your chart shows a range and not a prediction. Here is how to read it without fooling yourself in either direction.
The best tenth (teal)
Markets are kind and you got lucky. Useful to see, dangerous to plan around. Hope is not a strategy.
The median (green)
The middle future. Half of the simulations did better than this, half did worse. An honest center, not a promise.
The worst tenth (persimmon)
The unlucky futures, including bad returns early in retirement. This is the line that matters most. A plan that survives here is a plan you can trust.
The success rate
The share of all 10,000 futures where you never run out. Higher is safer, but no honest number reaches 100 percent.
The honest limits of any model.
The future is not the past
We sample from history, but markets can do things no history has recorded. A high success rate lowers risk; it never removes it.
Garbage in, garbage out
The numbers are only as good as the balances and spending you enter. Feed Glidepath garbage and it will hand you a confident, wrong answer.
We do not know your life
Health, family, job changes, and the things you cannot foresee are outside any model. Revisit your plan as life moves.
Laws will change
We model today's rules and update as they change, but decades of future policy are nobody's to predict.
Glidepath is a planning and education tool, not financial advice. Using it does not make us your advisor. For decisions with real money at stake, talk to a fiduciary who knows your whole situation. We would rather earn your trust by being precise than by overstating. Curious how we protect the numbers behind all this? Read about security.