Financial Tools

AI is a black box — it gives you an answer but hides its assumptions. Our tools show you the exact formula, let you change every assumption with a slider, and give you the same answer every time for the same inputs. In finance, transparency beats convenience.

Yes. Every calculation runs in your browser — your salary, savings, and debt numbers never touch our servers. You can optionally back up your data to your own Google Drive, which we never access.

Nominal return is what your account shows. Real return is what you can actually buy with that money after inflation. A 7% return with 3% inflation means your actual buying power only grew by ~4%. Our compound interest tool shows both.

The safe withdrawal rate (SWR) is the percentage of your portfolio you can withdraw each year without running out of money. The '4% rule' is a common starting point based on historical market data, calibrated by the Trinity Study (1998) for 30-year retirements. For early retirement (45-50 year horizons), a 3.3-3.5% rate is safer — our FIRE calculator runs the Monte Carlo simulation either way.

Every dollar you spend is a dollar that could have been invested. Opportunity cost is the growth you give up by choosing to spend. If you invest $10,000 at 7% for 20 years, it becomes ~$38,700 — so the true cost of spending that $10,000 today is really $38,700 in future value.

25× covers a 30-year retirement at 95% historical survival (the Trinity Study calibration). For early retirement at 45-50, that survival rate drops to 76-86% over a 50-year horizon — too thin for most planners. Use 28-33× expenses if you're aiming for early FIRE; the extra 5-8× is sequence-risk insurance, not over-saving.

It does two things at once. The cut reduces your FIRE target by $150K (at 25× expenses) AND adds $6K/year of investable surplus. The raise only adds the surplus — the target stays put. Same monthly dollars, roughly 2.7× faster path to FIRE because both levers move simultaneously.

Depends on your specific risk profile. Dual-earner couples in stable industries can sit at 3 months. Single-income households with kids and gig work need 9-12 months. Run the Emergency Fund calculator — it scores four risk factors (income concentration, dependents, job stability, unemployment insurance) and maps the total to 3 / 6 / 9 / 12 months, with the audit visible so you can adjust if you disagree with the weighting.