Full Control Over Your Financial Simulations
One-time purchase, yours forever. We're putting the finishing touches on it.
What's coming
Features and pricing subject to change.
| Feature | Free | Personal Edition |
|---|---|---|
| People | 1 | Unlimited |
| Portfolio Holdings | 3 presets | Custom |
| Return Distribution | Normal | Normal, Log-Normal, Historical, Correlated |
| Inflation | Fixed rate | Normal + Historical |
| Withdrawals | Simple % | Fixed, Dynamic, Smoothed + Guardrails |
| Contributions | Basic monthly | Custom frequency, growth, age ranges |
| Rebalancing | — | Target allocations + drift tolerance |
| One-Time Events | — | Lump sums, windfalls, expenses |
| Threshold Triggers | — | Conditional rules on portfolio value |
| Control Interface | — | Sliders, toggles & inputs to control your simulation |
| Save & Share | Share link | Save, revisit, share read-only links |
| Simulation Runs | 1,000 | 1,000 or 10,000 |
| Analytics | Portfolio, failure rate, distributions | Full charts, stats, yearly breakdowns |
| For personal use only. | Try for free |
Want to know the moment it's ready?
One email when we launch, then we delete your address. Nothing else.
Features in Detail
Your questions, your pace
Financial planning is inherently complex. A good advisor simplifies it for you — but they're also limited by what they can showcase in a session and explain with their tools. Some questions go unasked because there's no easy way to model them on the spot.
ButterflyForge puts the full complexity in your hands, on your own time. Ask "what if I retire two years earlier?" and see the answer in seconds. Wonder about a market crash in year three? Run it. Curious whether a guardrail strategy beats a fixed withdrawal? Compare them side by side. No appointment needed, no simplification required.
And when you want expert input, share your scenario with a financial advisor. They see exactly what you built, with all the assumptions visible. Better conversations, better advice — because you've already done the thinking.
People
Retirement rarely involves just one person. If you and your partner retire at different ages, have different life expectancies, or draw from the same portfolio at different rates, that changes everything. A plan that looks safe for one person's timeline can fall apart when a second person's needs overlap.
Free: One person. Personal: Unlimited people. Withdrawals, contributions, and life events can be tied to specific people, so you can model your household as it actually works.
Portfolio Holdings
Your portfolio isn't just "stocks and bonds." You might hold international equities, REITs, small-cap funds, inflation-protected bonds, or a mix of all of them. Each behaves differently, and how they move together during a downturn determines whether your portfolio weathers the storm or compounds the damage. Modeling your actual holdings gives you a much clearer picture of your real risk.
Free: Three preset portfolios (conservative, balanced, aggressive). Personal: Define any number of custom holdings with individual return profiles and volatilities. Model your actual portfolio.
Return Distribution Models
The return model you choose directly affects how often your simulation produces extreme outcomes. Normal distributions are the textbook default, but real markets crash harder and more often than a bell curve suggests. Log-normal models prevent impossible negative portfolio values. Historical bootstrapping replays actual market sequences. Correlated models capture how asset classes move together during crises. Choosing the right model helps you see the risks that simpler approaches miss.
Free: Normal distribution only. Personal: Normal, log-normal, historical bootstrap, and correlated multi-asset models. Pick the one that matches your assumptions about how markets behave.
Inflation Modeling
A fixed 2.5% inflation rate feels safe until you realize that inflation spikes early in retirement do far more damage than later ones. Your purchasing power erodes faster when you're spending the most, and the compounding effect over 30 years can double or triple your expenses. Variable inflation lets you see how sensitive your plan is to the timing, not just the average.
Free: Fixed inflation rate slider. Personal: Stochastic inflation that varies each year — normal distribution or based on historical patterns. See how your plan holds up when inflation doesn't cooperate.
Withdrawal Strategies
A fixed withdrawal rate is simple but rigid. In good years, you leave money on the table. In bad years, you drain your portfolio faster than necessary. Flexible strategies adapt: spend a bit more when markets are strong, pull back when they're not. The result is often more usable income over your lifetime and better protection against running out.
Guardrail strategies let you set hard spending limits — a floor you won't go below and a ceiling you won't exceed. Smoothed withdrawals prevent year-to-year spending whiplash. You can fine-tune all of this to match your own flexibility in spending and comfort with uncertainty.
Free: Simple percentage rate. Personal: Fixed, dynamic, smoothed, and guardrail strategies with configurable floors, ceilings, smoothing periods, and age-based rules.
Contributions
Your retirement doesn't start on day one of the simulation. Model the years of saving that come before: how much you contribute, how that grows with your salary, and when it stops. This lets you see the full picture — from your first regular investment to your last withdrawal — and understand how early decisions compound into later outcomes.
Free: Basic monthly contribution. Personal: Custom frequency, salary growth rate, start and end ages per person. Model the full lifecycle.
Portfolio Rebalancing
After a strong equity run, your portfolio can drift far from your intended allocation. That means more risk than you planned for, right when markets might be due for a correction. Rebalancing brings things back in line, but the method matters — how far you let it drift before acting, and whether you shift gradually or all at once. Simulating rebalancing lets you see how different approaches affect your long-term outcomes and risk exposure.
Free: Not available. Personal: Set target allocations with drift tolerance bands. Tie rebalancing to specific people and age ranges.
One-Time Events
An inheritance at 55 changes everything. So does a new roof at 68 or university fees for the kids. These aren't recurring expenses — they're singular events that can shift your plan's trajectory in one year. Ignoring them means your simulation doesn't reflect the life you're actually planning for.
Free: Not available. Personal: Add lump sum additions or withdrawals at specific ages. Model the events that matter to your plan.
Threshold Triggers
Sometimes the right action depends on where your portfolio is, not just when you are. "If my portfolio drops below 300k, cut spending by 20%." "If it exceeds 2M, gift 50k to the kids." "If below 500k and I'm still younger than 75, scale back withdrawals." These conditional rules combine portfolio value with age and let your simulation respond to market outcomes the way you would in real life.
Free: Not available. Personal: Conditional rules that fire based on portfolio value, age, or both. Trigger withdrawals, contributions, or one-time actions automatically.
Control Interface
The most valuable question in retirement planning is "what if?" What if I retire at 60 instead of 65? What if my withdrawal rate is 3.5% instead of 4%? The Control Interface lets you define sliders, toggles, and inputs that other modules reference. Change one value and instantly see the effect across your entire scenario. No hunting through settings, no risk of forgetting one. Just change the control and compare.
Free: Not available. Personal: Define named controls. Other modules reference them. Change one value, update everything.
Simulation Runs
More runs means better resolution on the outcomes that matter most — especially the bad ones. With 1,000 runs you get a solid picture. With 10,000, you see tail risks more clearly: those rare but devastating scenarios where everything goes wrong at once. If you're making real decisions based on your simulation, the extra confidence is worth it.
Free: 1,000 runs. Personal: 1,000 or 10,000 runs.
Analytics
Knowing your failure rate is a start, but it doesn't tell you why plans fail or when things start to go wrong. The Personal Edition lets you track any value's distribution year by year, see how often triggers fire, visualize withdrawal and contribution ranges over time, and spot the years where your plan is most vulnerable. More angles, better intuition.
Free: Portfolio projections, failure rate, withdrawal and portfolio value distributions. Personal: All of the above plus yearly value distributions, trigger frequency tracking, and detailed range analysis.
Don't miss the launch
One email when it's ready. We'll delete your address right after.
One email when we launch, then we delete your address. Nothing else.
This tool provides statistical simulations based on historical data and modeled assumptions. Results are not predictions or guarantees of future performance. This is not financial advice. The creators accept no liability for decisions made based on these simulations. Please seek professional financial advice before making investment decisions.