Future wealth projections are inherently uncertain — the difference between a 5% and 9% annual return over 25 years can more than double your final net worth. Most calculators hide this uncertainty behind a single estimate. The Future Net Worth Simulator makes it explicit: enter your financial inputs once and see three parallel projections — pessimistic (5%), base case (7%), and optimistic (9%) — so you can plan for the realistic range of outcomes rather than a single line that may or may not materialize. Beyond the projection itself, the calculator integrates FIRE analysis: based on your monthly expenses, it calculates your FIRE number (25× annual expenses — the 4% rule threshold) and determines at what age each scenario would make work financially optional. This FIRE age is often the most actionable output: it shows whether your current trajectory leads to financial independence on a reasonable timeline, and what changes to savings rate or expenses would accelerate or delay that date. The simulator also shows the decade-by-decade breakdown: where you'll be at 10 years, 20 years, and 30 years under each scenario, with the split between your contributions and compound interest to illustrate how the growth engine shifts from savings-driven to interest-driven over time.