Monte Carlo simulation
Available on Plus and ProSee the range, not just one retirement date
Run your FI plan through 10,000 simulated market paths. See how likely you are to reach your target by a date, when you're likely to get there, and whether your retirement income lasts.
Monte Carlo is included in Plus and Pro · Start on Free, no card required
Illustrative demo plan, computed by Yield Clarity's simulation engine. Results are estimates, not predictions.
Why one path isn't enough
Markets don't deliver an average return every year
The expected path assumes a steady return, so it gives one date. Real returns arrive unevenly, and the order matters, especially once you start withdrawing. Monte Carlo replays your plan thousands of times with returns that vary.
What the simulation shows
Four answers from the same 10,000 paths
Each result sits alongside your expected path, using the same plan and assumptions.
- Probability of reaching FI
The share of paths that reach your FI target by a date you choose (by default, your expected-path date).
Demo plan: 48% by Jun 2035 (4,837 of 10,000 paths)
- Likely FI window
The middle half of FI dates among the paths that get there, with the median date alongside.
Demo plan: October 2033 – November 2037
- Range of outcomes
How widely portfolio values spread over time, around the median outcome.
Demo plan: 50% and 80% bands
- Retirement spending funded
The share of paths whose money lasts 5 to 20 years past retirement (15 by default) while you draw your income.
Demo plan: 99% through May 2050
Reading the probability
A share of simulated paths, not a forecast
About 48% of simulated paths (4,837 of 10,000) reached the target by June 2035. It describes your assumptions; it isn't the chance that real markets will behave this way.
- It reflects the assumptions you chose. Change them and it changes.
- Early-retirement risk is shown separately, because weak first years can matter more than the average.
- Compare results after changing one input, rather than chasing a single number.
Inputs
What goes into each path
Your plan supplies the starting point, contributions and retirement income. The market assumptions are fixed and shown with every result.
- Simulated paths
- Monthly steps, repeatable results
- 10,000
- Average return
- Your planning return, less a 0.2% fee allowance
- 6.2%
- Volatility
- From fixed asset-class assumptions for your FI-eligible mix
- 11.4% a year
- Inflation
- Varies path by path, loosely linked to returns
- 2.5% on average
- Contributions and income
- Contribution phases, retirement income and withdrawal strategy
- From your plan
What the model leaves out
Limitations- Smooth, simple markets
- Returns follow a log-normal pattern: no fat tails or regime changes, and asset classes are treated as uncorrelated.
- One portfolio
- Your FI-eligible assets move together as one portfolio; individual holdings aren't simulated.
- Before tax
- No tax, state pension or defined benefit income in the simulated paths.
- Planning, not advice
- Probabilities describe your assumptions. They are not a recommendation or a guarantee.
Questions
Monte Carlo, answered
Which plans include Monte Carlo?
Monte Carlo is included in Plus and Pro. You can create a Free account without a card, build your plan and see its expected path, then upgrade when you want the probability view.
Compare plansIs a 50% probability bad?
Not necessarily. It is measured at your expected-path date, and because simulated returns average out to your planning return, roughly half of paths tend to arrive by then. The likely window often says more than one number.
Does the simulation include tax, state pensions or defined benefit income?
No. The simulation models your FI-eligible portfolio, contributions and retirement withdrawals before tax. State pension and defined benefit income are not added to the simulated paths.
Why do my results not change each time I run it?
The simulation uses a fixed random seed, so the same plan gives the same result. Changes you see come from changes to your plan or assumptions, not from chance.
Test your plan against thousands of futures
Build your plan free and see its expected path. Monte Carlo is included in Plus and Pro.
No card required for the Free plan.