{
  "slug": "compound-interest",
  "title": "Compound Interest Calculator",
  "heading": "Compound Interest Calculator",
  "category": "financial",
  "url": "https://www.revenuelab.fyi/toolbox/compound-interest",
  "summary": "See how a lump sum grows with compounding over time.",
  "description": "Project the future value of a starting balance compounded at a chosen frequency.",
  "formula": "FV = P × (1 + r/n)^(n·t)",
  "dateModified": "2026-10-03",
  "run_url": "https://www.revenuelab.fyi/api/public/calc?tool=compound-interest",
  "inputs": [
    {
      "id": "principal",
      "label": "Starting amount",
      "kind": "number",
      "hint": null,
      "default": 10000,
      "unit": "$",
      "min": 0,
      "max": null
    },
    {
      "id": "rate",
      "label": "Annual rate",
      "kind": "number",
      "hint": null,
      "default": 6,
      "unit": "%",
      "min": -50,
      "max": null
    },
    {
      "id": "years",
      "label": "Years",
      "kind": "number",
      "hint": null,
      "default": 10,
      "unit": "years",
      "min": 0,
      "max": 80
    },
    {
      "id": "freq",
      "label": "Compounding",
      "kind": "select",
      "hint": null,
      "default": "12",
      "options": [
        {
          "value": "1",
          "label": "Annually"
        },
        {
          "value": "2",
          "label": "Semi-annually"
        },
        {
          "value": "4",
          "label": "Quarterly"
        },
        {
          "value": "12",
          "label": "Monthly"
        },
        {
          "value": "365",
          "label": "Daily"
        }
      ]
    }
  ],
  "outputs": [
    {
      "id": "future",
      "label": "Future value",
      "format": "currency",
      "hint": null,
      "primary": true
    },
    {
      "id": "earnings",
      "label": "Interest earned",
      "format": "currency",
      "hint": null,
      "primary": false
    }
  ],
  "worked_example": {
    "inputs": [
      "Starting amount: 10000 $",
      "Annual rate: 6 %",
      "Years: 10 years",
      "Compounding: Monthly"
    ],
    "outputs": [
      "Future value: $18,193.97",
      "Interest earned: $8,193.97"
    ]
  },
  "how_to": {
    "title": "How to use this",
    "steps": [
      "Enter starting amount ($).",
      "Enter annual rate (%).",
      "Enter years (years).",
      "Enter compounding.",
      "Read your future value 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": {
        "principal": 6000,
        "rate": 6,
        "years": 6,
        "freq": "12"
      }
    },
    {
      "name": "Typical",
      "description": "Defaults — the most common real-world setup.",
      "values": {
        "principal": 10000,
        "rate": 6,
        "years": 10,
        "freq": "12"
      }
    },
    {
      "name": "Ambitious",
      "description": "Higher-end numbers — what if things really pop?",
      "values": {
        "principal": 16000,
        "rate": 6,
        "years": 16,
        "freq": "12"
      }
    }
  ],
  "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 compound interest calculator work?",
      "a": "Project the future value of a starting balance compounded at a chosen frequency. The underlying maths is: FV = P × (1 + r/n)^(n·t)"
    },
    {
      "q": "What do I need to enter?",
      "a": "4 values: starting amount, annual rate, years, and compounding. 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 future value 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/investment",
    "https://www.revenuelab.fyi/toolbox/savings",
    "https://www.revenuelab.fyi/toolbox/cd"
  ],
  "license": "CC-BY-4.0",
  "citation": "RevenueLab — Compound Interest Calculator (https://www.revenuelab.fyi/toolbox/compound-interest)"
}