Why the fire number progress calculator matters
FIRE maths is unusually sensitive to the savings rate, because every extra dollar saved both raises the balance and lowers the spending the balance has to fund. This page turns that decision into a handful of inputs you can defend in a budget review: volume, unit cost, rate of adoption, and time. The output is a planning baseline, not a promise — it tells you whether the idea deserves a vendor quote, a pilot, or a pass.
- • Biggest swing factor: your savings rate, which moves both sides of the equation
- • Second-order factor: the balance already invested
- • Often ignored: the return you assume over the accumulation years
What actually changes the answer
your savings rate, which moves both sides of the equation moves this number first, then the balance already invested. Run a conservative case and an upside case before you commit. If the maths only works in the upside case, treat it as a time-boxed test with a kill date rather than a line in next year's plan.
What to do with the result
Model a leaner spending year alongside the base case. Cutting the target is usually faster than earning your way to the original one.
Related guides
Long-form playbooks on the same topic, written by the RevenueLab editorial team.
FAQ
What does the fire number progress calculator work out?
It applies Net worth = assets − liabilities; Future = net worth × (1 + r)^years + annual savings × [((1 + r)^years − 1) ÷ r] to the values you enter for total assets you own, total debts you owe, monthly savings added, assumed annual growth rate, years to project. FIRE maths is unusually sensitive to the savings rate, because every extra dollar saved both raises the balance and lowers the spending the balance has to fund.
How accurate is this fire number progress calculator?
Projects a balance, not a withdrawal plan. Sequence-of-returns risk and healthcare costs need separate modelling. Replace the defaults with your own invoice, usage export, payroll data, statement, or vendor quote before making a commitment — the maths is exact, so the answer is only as good as the inputs you feed it.
Which input should I stress-test first?
your savings rate, which moves both sides of the equation. Re-run with a pessimistic value for it; if the decision flips, that assumption is the thing you need real data on before signing anything. After that, check the balance already invested and the return you assume over the accumulation years.
Which scenario should I start from?
Start with the preset closest to your situation — conservative, base case, aggressive saver — then edit the sliders. Presets are realistic starting points, not benchmarks to match, and every change updates the result instantly.
What should I do after running the numbers?
Model a leaner spending year alongside the base case. Cutting the target is usually faster than earning your way to the original one. A useful planning benchmark to compare against: The 4% rule implies a FIRE number near 25× annual spending.
Can I share or save this calculation?
Yes. Your inputs are written into the page URL, so copying the link shares the exact scenario you are looking at — the person who opens it sees the same numbers. You can also export the inputs and results to CSV or PDF from the result card and keep it with the rest of your workings.
How this calculator is built
Independently maintained
Written by Sam Doshi and the RevenueLab editorial team. We don't sell the data feeds this tool is built on.
Sourced from primary data
Benchmarks come from public AdSense / Stripe / IRS disclosures and reader-submitted data — never third-party "$X per view" claims. Full methodology.
Last editorial review
Reviewed on a rolling quarterly cycle. Dated reviews are published on the methodology record for each calculator.
Editorial standards
See our editorial policy and disclaimer. Results are estimates, not advice.