Coast FIRE Calculator
A Coast FIRE calculator determines when you've saved enough that compound growth alone will fund your retirement—without any additional contributions. Once you reach Coast FIRE, you only need to cover current expenses.
Coast FIRE Formula
Coast FIRE Number = FIRE Number ÷ (1 + return)^years to retirement
Coast FIRE Numbers by Age
Target: $1,500,000 at age 65, 7% real returns:
| Current Age | Years to 65 | Coast FIRE Number | 2540$100,265 3035$140,559 3530$197,099 4025$276,402 4520$387,628 | 50 | 15 | $543,587 |
Coast FIRE Calculator Implementation
``javascript
function calculateCoastFIRE(targetFIRE, currentAge, retireAge, returnRate) {
const yearsToRetire = retireAge - currentAge;
const r = returnRate / 100;
// Present value of target FIRE number
const coastFIRE = targetFIRE / Math.pow(1 + r, yearsToRetire);
return {
coastFIRE: coastFIRE.toFixed(2),
yearsToRetire,
growthMultiple: Math.pow(1 + r, yearsToRetire).toFixed(2),
targetFIRE
};
}
console.log(calculateCoastFIRE(1500000, 35, 65, 7));
// { coastFIRE: '197099', yearsToRetire: 30, growthMultiple: '7.61' }
function checkIfCoasting(currentSavings, targetFIRE, currentAge, retireAge, returnRate) {
const coastNumber = calculateCoastFIRE(targetFIRE, currentAge, retireAge, returnRate);
const isCoasting = currentSavings >= parseFloat(coastNumber.coastFIRE);
return {
...coastNumber,
currentSavings,
isCoasting,
gap: (parseFloat(coastNumber.coastFIRE) - currentSavings).toFixed(2)
};
}
``
After Coast FIRE
Once coasting, you can take lower-paying but more fulfilling work, work part-time, or take career risks—as long as you cover current expenses. Your investments grow on autopilot to your retirement number.