FIRE Calculator — Retire Early Scenarios

What you get

A single Excel workbook that models five distinct FIRE paths — Lean, Regular, Fat, Coast, and Barista — from one set of inputs, with no macros or external dependencies. Years-to-FI calculations run through Excel's native NPER function, then stress-tested across sequence-of-returns scenarios and a Monte Carlo percentile range so you see not just when you might retire, but how reliably.

Who it's for

Built for FIRE planners who are past the basics and want a rigorous side-by-side comparison of their options — whether you're deciding between coasting at 40 or grinding toward fat-FIRE at 50, or simply need to know how much a lifestyle change reshapes your timeline before you commit to it.

What's inside

• Dashboard sheet — enter current age, savings balance, monthly contributions, expected return, planned retirement expenses, and withdrawal rate once; all six sheets recalculate automatically.
• Five-path FI comparison — Lean, Regular, Fat, Coast, and Barista FIRE scenarios computed in parallel, each returning a years-to-FI figure from the same core inputs.
• Sequence-of-returns stress test — three scenarios (favorable, average, adverse early returns) applied to each path to surface withdrawal sustainability risk that a single-rate model hides.
• Monte Carlo percentile sheet — five return percentiles (10th through 90th) give a probability-weighted range around each FI date without requiring add-ins or external tools.
• Sensitivity analysis sheet — quantifies exactly how a 15% increase in projected retirement expenses shifts nest-egg targets and extends timelines across every FIRE path simultaneously.
• Withdrawal sustainability output — flags which paths remain solvent under each stress scenario, anchored to your specified safe withdrawal rate.

How to use it

Open the file in Microsoft Excel (2016 or later) or Google Sheets — no macros to enable and no external data connections to configure. Fill in the six input fields on the Dashboard sheet and every scenario, stress test, and sensitivity calculation updates immediately across all sheets.