{
  "slug": "coast-fire",
  "title": "Coast FIRE Calculator",
  "heading": "Coast FIRE Calculator",
  "category": "financial",
  "url": "https://www.revenuelab.fyi/toolbox/coast-fire",
  "summary": "The balance where you can stop saving and still retire on time.",
  "description": "Coast FIRE is the point where compounding alone gets you to your number. Hitting it does not mean quitting — it means you only need to cover current expenses from here.",
  "formula": "Coast number = Target ÷ (1 + real return)^(years to retirement).",
  "dateModified": "2026-09-30",
  "run_url": "https://www.revenuelab.fyi/api/public/calc?tool=coast-fire",
  "inputs": [
    {
      "id": "current",
      "label": "Current invested balance",
      "kind": "number",
      "hint": null,
      "default": 180000,
      "unit": "$",
      "min": 0,
      "max": null
    },
    {
      "id": "age",
      "label": "Current age",
      "kind": "number",
      "hint": null,
      "default": 34,
      "unit": null,
      "min": 15,
      "max": 80
    },
    {
      "id": "retireAge",
      "label": "Retirement age",
      "kind": "number",
      "hint": null,
      "default": 65,
      "unit": null,
      "min": 30,
      "max": 90
    },
    {
      "id": "spend",
      "label": "Annual spending in retirement (today's dollars)",
      "kind": "number",
      "hint": null,
      "default": 60000,
      "unit": "$",
      "min": 0,
      "max": null
    },
    {
      "id": "swr",
      "label": "Safe withdrawal rate",
      "kind": "number",
      "hint": null,
      "default": 4,
      "unit": "%",
      "min": 2,
      "max": 8
    },
    {
      "id": "realReturn",
      "label": "Real return after inflation",
      "kind": "number",
      "hint": null,
      "default": 6,
      "unit": "%",
      "min": 0,
      "max": 12
    }
  ],
  "outputs": [
    {
      "id": "coast",
      "label": "Coast FIRE number",
      "format": "currency",
      "hint": null,
      "primary": true
    },
    {
      "id": "gap",
      "label": "Still needed to coast",
      "format": "currency",
      "hint": null,
      "primary": false
    },
    {
      "id": "coastPct",
      "label": "Progress to Coast FIRE",
      "format": "percent",
      "hint": null,
      "primary": false
    },
    {
      "id": "target",
      "label": "Full FIRE number",
      "format": "currency",
      "hint": null,
      "primary": false
    },
    {
      "id": "projected",
      "label": "Projected balance at retirement",
      "format": "currency",
      "hint": null,
      "primary": false
    },
    {
      "id": "surplus",
      "label": "Surplus or shortfall vs target",
      "format": "currency",
      "hint": null,
      "primary": false
    }
  ],
  "worked_example": {
    "inputs": [
      "Current invested balance: 180000 $",
      "Current age: 34",
      "Retirement age: 65",
      "Annual spending in retirement (today's dollars): 60000 $",
      "Safe withdrawal rate: 4 %",
      "Real return after inflation: 6 %"
    ],
    "outputs": [
      "Coast FIRE number: $246,382.26",
      "Still needed to coast: $66,382.26",
      "Progress to Coast FIRE: 73.1%",
      "Full FIRE number: $1,500,000.00",
      "Projected balance at retirement: $1,095,858.12",
      "Surplus or shortfall vs target: -$404,141.88"
    ]
  },
  "how_to": {
    "title": "How to use this",
    "steps": [
      "Enter current invested balance ($).",
      "Enter current age.",
      "Enter retirement age.",
      "Enter annual spending in retirement (today's dollars) ($).",
      "Enter safe withdrawal rate (%).",
      "Enter real return after inflation (%).",
      "Read your coast fire number on the right — it updates as you type.",
      "Hit Share to keep the scenario or send it to someone."
    ]
  },
  "scenarios": [
    {
      "name": "Conservative",
      "description": "Lower-end numbers — what if things land soft?",
      "values": {
        "current": 108000,
        "age": 34,
        "retireAge": 39,
        "spend": 36000,
        "swr": 2.4,
        "realReturn": 3.5999999999999996
      }
    },
    {
      "name": "Typical",
      "description": "Defaults — the most common real-world setup.",
      "values": {
        "current": 180000,
        "age": 34,
        "retireAge": 65,
        "spend": 60000,
        "swr": 4,
        "realReturn": 6
      }
    },
    {
      "name": "Ambitious",
      "description": "Higher-end numbers — what if things really pop?",
      "values": {
        "current": 288000,
        "age": 34,
        "retireAge": 90,
        "spend": 96000,
        "swr": 6.4,
        "realReturn": 9.600000000000001
      }
    }
  ],
  "limitations": [
    "Results are estimates before tax, fees, and inflation unless an input explicitly covers them.",
    "Rates are treated as fixed for the whole period — variable-rate products will drift from this projection.",
    "This is educational maths, not financial advice. Check anything contractual with the lender or your accountant."
  ],
  "faq": [
    {
      "q": "How does the coast fire calculator work?",
      "a": "Coast FIRE is the point where compounding alone gets you to your number. Hitting it does not mean quitting — it means you only need to cover current expenses from here. The underlying maths is: Coast number = Target ÷ (1 + real return)^(years to retirement)."
    },
    {
      "q": "What do I need to enter?",
      "a": "6 values: current invested balance, current age, retirement age, annual spending in retirement (today's dollars), safe withdrawal rate, and real return after inflation. Each field starts with a sensible default, so you can change one number at a time and watch the result move."
    },
    {
      "q": "What does the coast fire number result mean?",
      "a": "It is returned as a money amount in US dollars and updates live as you edit the inputs, so you can compare two or three versions of a scenario in a few seconds."
    },
    {
      "q": "Is this calculator free, and do I need an account?",
      "a": "Yes, it's free, and no account is required. Nothing you type is stored on our servers — the maths runs entirely in your browser."
    },
    {
      "q": "How accurate is the result?",
      "a": "It applies the standard formula exactly, so the arithmetic is precise. Results are estimates before tax, fees, and inflation unless an input explicitly covers them."
    },
    {
      "q": "Who is this tool for?",
      "a": "It's built for anyone comparing money scenarios before committing — budgeting a payment, sanity-checking a quote, or seeing what a change in rate or term actually costs."
    }
  ],
  "related": [
    "https://www.revenuelab.fyi/toolbox/safe-withdrawal-rate",
    "https://www.revenuelab.fyi/toolbox/portfolio-rebalance"
  ],
  "license": "CC-BY-4.0",
  "citation": "RevenueLab — Coast FIRE Calculator (https://www.revenuelab.fyi/toolbox/coast-fire)"
}