{
  "slug": "sinking-fund",
  "title": "Sinking Fund Calculator",
  "heading": "Sinking Fund Calculator",
  "category": "financial",
  "url": "https://www.revenuelab.fyi/toolbox/sinking-fund",
  "summary": "Monthly set-aside for a known future expense.",
  "description": "Sinking funds turn irregular expenses — insurance premiums, holidays, new tires — into a predictable monthly line item so they never become credit card debt.",
  "formula": "Monthly = (Goal − saved) ÷ months remaining.",
  "dateModified": "2026-09-30",
  "run_url": "https://www.revenuelab.fyi/api/public/calc?tool=sinking-fund",
  "inputs": [
    {
      "id": "goal",
      "label": "Total needed",
      "kind": "number",
      "hint": null,
      "default": 3600,
      "unit": "$",
      "min": 0,
      "max": null
    },
    {
      "id": "saved",
      "label": "Already saved",
      "kind": "number",
      "hint": null,
      "default": 400,
      "unit": "$",
      "min": 0,
      "max": null
    },
    {
      "id": "months",
      "label": "Months until you need it",
      "kind": "number",
      "hint": null,
      "default": 10,
      "unit": null,
      "min": 1,
      "max": 120
    },
    {
      "id": "apy",
      "label": "Savings APY",
      "kind": "number",
      "hint": null,
      "default": 4,
      "unit": "%",
      "min": 0,
      "max": 10
    }
  ],
  "outputs": [
    {
      "id": "monthly",
      "label": "Save this much per month",
      "format": "currency",
      "hint": null,
      "primary": true
    },
    {
      "id": "weekly",
      "label": "Weekly equivalent",
      "format": "currency",
      "hint": null,
      "primary": false
    },
    {
      "id": "perPaycheck",
      "label": "Per biweekly paycheck",
      "format": "currency",
      "hint": null,
      "primary": false
    },
    {
      "id": "gap",
      "label": "Amount still needed",
      "format": "currency",
      "hint": null,
      "primary": false
    },
    {
      "id": "total",
      "label": "Total you will contribute",
      "format": "currency",
      "hint": null,
      "primary": false
    },
    {
      "id": "interest",
      "label": "Interest earned along the way",
      "format": "currency",
      "hint": null,
      "primary": false
    }
  ],
  "worked_example": {
    "inputs": [
      "Total needed: 3600 $",
      "Already saved: 400 $",
      "Months until you need it: 10",
      "Savings APY: 4 %"
    ],
    "outputs": [
      "Save this much per month: $313.90",
      "Weekly equivalent: $72.44",
      "Per biweekly paycheck: $156.95",
      "Amount still needed: $3,200.00",
      "Total you will contribute: $3,138.96",
      "Interest earned along the way: $61.04"
    ]
  },
  "how_to": {
    "title": "How to use this",
    "steps": [
      "Enter total needed ($).",
      "Enter already saved ($).",
      "Enter months until you need it.",
      "Enter savings apy (%).",
      "Read your save this much per month 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": {
        "goal": 2200,
        "saved": 250,
        "months": 6,
        "apy": 2.4
      }
    },
    {
      "name": "Typical",
      "description": "Defaults — the most common real-world setup.",
      "values": {
        "goal": 3600,
        "saved": 400,
        "months": 10,
        "apy": 4
      }
    },
    {
      "name": "Ambitious",
      "description": "Higher-end numbers — what if things really pop?",
      "values": {
        "goal": 5800,
        "saved": 650,
        "months": 16,
        "apy": 6.4
      }
    }
  ],
  "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 sinking fund calculator work?",
      "a": "Sinking funds turn irregular expenses — insurance premiums, holidays, new tires — into a predictable monthly line item so they never become credit card debt. The underlying maths is: Monthly = (Goal − saved) ÷ months remaining."
    },
    {
      "q": "What do I need to enter?",
      "a": "4 values: total needed, already saved, months until you need it, and savings apy. 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 save this much per month 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/emergency-fund",
    "https://www.revenuelab.fyi/toolbox/budget-50-30-20"
  ],
  "license": "CC-BY-4.0",
  "citation": "RevenueLab — Sinking Fund Calculator (https://www.revenuelab.fyi/toolbox/sinking-fund)"
}