The Coast FIRE Calculator is a free, browser-based tool for people in their 30s and 40s who want to stop saving for retirement without quitting work. Enter a few numbers and it shows the lump sum you need today so your portfolio can grow into a full retirement number on its own — the Coast FIRE number.
Coast FIRE (often written “Coast FI”) is the point where your invested assets are large enough that, left to compound at your expected return, they will reach your full FIRE number by your target retirement age — without any additional contributions. After reaching it you can stop saving for retirement and still arrive on time.
Inputs: your current age, invested assets, annual spending, annual savings, expected return (default 7%), inflation (default 3%), safe withdrawal rate (default 4%), and target retirement age (default 65). Outputs: your Coast FIRE number, the age you reach it, a progress bar against today’s target, a year-by-year growth chart in today’s dollars, and a shareable result link.
First, your full FI number is annual spending divided by the safe withdrawal rate. The Coast FIRE number is that future FI number discounted back to today at your real (inflation-adjusted) rate of return. The tool compounds your current assets and annual savings each year, subtracts inflation, and tells you when your balance crosses the Coast FIRE threshold.
US savers in their 30s and 40s who want to reduce retirement contributions while staying at work. The tool is an estimate, not personalized financial advice — actual returns and inflation will differ from your assumptions.
Every calculation runs locally in your browser. Nothing you enter is uploaded, stored, or transmitted. The site is free, requires no account for the calculator, and never sells data.
Questions or feedback? Email [email protected].