Inputs
Example Data Table
| Scenario | Current | Monthly Contrib | Spend / mo | Return % | Inflation % | SWR % | |
|---|---|---|---|---|---|---|---|
| LeanFIRE | 25000 | 800 | 1500 | 7 | 2 | 4 | |
| CoastFIRE | 120000 | 500 | 2500 | 6 | 2.5 | 3.5 | |
| FatFIRE | 350000 | 1500 | 5000 | 6.5 | 2 | 3.5 |
Formulae Used
- Annual spending:
S = 12 × monthly_spending - FI target (4% rule example):
FI = S / (SWR/100) - Real return:
r = (1 + r_nominal) / (1 + inflation) − 1 - Projection (end‑of‑year contributions):
FV(n) = PV × (1+r)^n + PMT × [((1+r)^n − 1)/r]
In the table we also iterate year by year to show progress versus the FI target.
Assumptions ignore taxes and fees and treat contributions as constant in real terms.
Results
—
FI number (real)
—
Estimated years to FI
—
Estimated age at FI
| Year | Age | Start Balance | Contrib | End Balance | FI Target |
|---|
Pro tip: Use a more conservative withdrawal rate or add a margin of safety if your portfolio is concentrated or your income needs might rise.