FIcology 101

Getting started

• Fill in the Inputs tab on the left — the chart, table, and summary cards update instantly. Use the Assumptions tab for return rates and the Settings tab for projection length and table options.
• Annual / Monthly toggle (bottom of the Inputs tab) lets you type Contribution and Expenses as yearly or monthly amounts, whichever is easier — calculations and table rows are always annual-based.
• The table auto-switches to retirement withdrawals at your Target Retire Age. Your FI Number is shown as a milestone — it auto-calculates from Annual Expenses ÷ Safe Withdrawal Rate, or type a value to override it and click ↺ Reset to auto-calculate to go back.
• In the table, the Contribution / Withdrawal and Return % columns are editable (pencil icon in header). Click any cell to override it for a specific year. An amber highlight and ↺ icon appear when a cell has a manual override — click ↺ to restore just that cell to its calculated default.
• Phase Fill Down (Settings tab) cascades a cell edit to all rows below it within the same phase. Stops at Accumulation → Coasting → Retirement boundaries so edits don't accidentally overwrite other phases.
• Auto-Coast (Settings tab) automatically switches to $0 contributions once you hit Coast FI, letting compound growth carry you the rest of the way to retirement.
• Clear Manual Table Edits (link below the input panel) removes all cell overrides at once and restores the calculated defaults. Reset Calculator, next to it (shown only once anything's been changed), goes further — it also resets every input, assumption, and setting back to default and clears your saved data on this device.
• Your inputs, table edits, and settings are automatically saved on this device and restored next time you visit — nothing is sent anywhere, it stays in your browser. The 🔗 link icon (top-right of the input panel, next to the tabs) copies a share link that restores your Inputs, Assumptions, and Settings for you or someone else on any device — table edits aren't included in the link.
• Phase colors: blue = accumulation, yellow = coasting (no contributions, not yet withdrawing), green = retirement.

Scenarios & tips

• Simulate a market crash: click a Return % cell and enter a negative number (e.g., -20%). Repeat for each crash year. Click ↺ on each cell when done to restore it.
• Sabbatical or career break: override the Contribution cell to $0 for the years you won't be saving.
• Big one-time expense: enter a large negative number in a Contribution cell (e.g., -$50,000 for a home down payment) — it pulls that amount from the portfolio that year.
• Part-time income in retirement: override a retirement year's withdrawal cell to a smaller negative number, or even a positive number if your part-time income covers expenses.
• Lean FIRE vs. Fat FIRE: type a custom value in the FI Number field to compare different savings targets.
• Variable spending in retirement: override individual retirement withdrawal cells to model spending less during a market downturn.
• See the coast FI effect: check Auto-Coast and watch your FI Date — sometimes stopping contributions early moves your FI date by only a year or two; sometimes much more.