FIRE Number Calculator
The FIRE Number Calculator shows the amount of invested wealth needed to support your lifestyle indefinitely, translating yearly spending into a clear financial independence target using a sustainable withdrawal rate. It’s useful when you’re mapping an exit from mandatory work, stress-testing retirement timing, or comparing how choices—housing, location, or lifestyle upgrades—shift the finish line.
This tool lets us run practical “what-ifs” to shape a plan: tighten or expand spending, consider safer withdrawal assumptions, and see how saving more or earning extra accelerates the path. The goal is a concrete, confidence-building number and roadmap—so you can focus on the highest-impact levers, track momentum over time, and make trade-offs that bring work-optional living within reach.
Financial independence target & timeline — we compute a target portfolio from your annual spending and SWR, then estimate years to FI using your current portfolio, monthly contributions, and expected annual return.
We estimate a FIRE number from your annual spending and a chosen safe withdrawal rate (SWR), then project years to FI using your current portfolio, monthly contributions, and expected return. Use this as a planning guide—adjust assumptions to pressure-test the path.
We assume contributions at month-end and constant returns. Real paths vary—rerun with different assumptions to bracket outcomes.
Results interpretation
How it works
We use a standard future-value model with end-of-month contributions and a constant annual return split into monthly steps.
Formulas, assumptions, limitations
FIRE number. Target = Annual spending ÷ SWR. Example: $50,000 ÷ 4% = $1,250,000.
Monthly growth. Monthly factor m = (1 + r)^(1/12), where r is expected annual return.
Future value with deposits. FV = P·m^n + C·((m^n − 1)/(m − 1)), contributions at month-end.
Solve for months. m^n = (Target + C/(m−1)) ÷ (P + C/(m−1)), then n = ln(...) ÷ ln(m). We fall back to iteration if the closed-form is invalid.
Assumptions. Constant spending, constant SWR and return, no taxes/fees in growth estimate.
Limitations. Markets are volatile; taxes and inflation matter. Treat results as planning estimates, not guarantees.
Use cases & examples
Annual spend $48,000; SWR 4%; target $1.2M. With $300k saved, $1,500/mo contributions, and 6% return, we get a rough timeline to FI.
If we prefer 3.5% SWR, the target rises. We can offset by increasing contributions or accepting a longer path.
Temporarily doubling contributions during high-earning years can shave multiple years off the FI timeline.
FIRE FAQs
What SWR should we use?
Many planners start at 4% for long horizons, then adjust down for conservatism or higher sequence-of-returns risk. Try a range (3%–5%).
Do we include Social Security or pensions?
You can reduce required spending by expected external income sources. Lower spend → lower target.
How do taxes fit in?
Spending should be after-tax. If our withdrawals are taxable, increase the spending figure or lower SWR to compensate.
Why end-of-month contributions?
It’s conservative and matches typical payroll timing. Beginning-of-month contributions reach FI slightly faster.
What about inflation?
SWR is typically a real (after-inflation) rule. Keep spending in today’s dollars for consistency and revisit annually.
Unreachable results?
If contributions are too small relative to return or return is negative, the target may be unreachable. Adjust spend, SWR, return, or contributions.
Charting the path to financial independence
Financial independence is a math problem wrapped in life choices. Our goal is to translate those choices—how much we spend, how much we can save, and how we invest—into a clear target and a believable path. With a few inputs, we can see how fast the flywheel turns and which levers move it most.
Start with spending, not returns
Spending drives the target. We can’t invest our way out of undisciplined spending. If we tighten recurring costs, the target shrinks and the timeline shortens. One dollar less in annual spending lowers the target by roughly 1 ÷ SWR dollars.
Pick an SWR and sanity-check it
SWR is a design choice. Higher SWR means a smaller target but thinner safety margins. Lower SWR means a bigger target and a longer path but higher resilience to poor early returns. We like to test 3.5%, 4.0%, and 4.5% to understand trade-offs.
Contributions are the engine
Returns get the headlines, but contributions drive early progress. Automating savings, capturing employer matches, and routing windfalls can move the needle years sooner than chasing a small return edge.
Sequence risk and buffers
The order of market returns matters. Poor early returns can stress withdrawals even if the long-run average is fine. Buffers like a year of cash, flexible spending, or part-time income improve durability without requiring heroic returns.
Milestones
- 25× rule: Spend × 25 is a quick 4% SWR estimate.
- Halfway checks: When progress hits 50%, compounding accelerates. Stay the course.
- Glidepath: As we approach FI, consider dialing risk to match the plan’s fragility.
Make the plan your own
The best plan is one we’ll actually follow. Tune the inputs, revisit annually, and adjust the route as life changes. Financial independence isn’t a single date—it’s a range. With clarity on the math, we can make better choices all along the way.
Bottom line
Control what’s controllable—spending and saving. Invest simply, stay diversified, and let time do the compounding. The numbers here turn a big goal into small levers we can pull today.