{
  "slug": "simple-interest",
  "title": "Simple Interest Calculator",
  "heading": "Simple Interest Calculator",
  "category": "financial",
  "url": "https://www.revenuelab.fyi/toolbox/simple-interest",
  "summary": "Interest = P × r × t (no compounding).",
  "description": "Compute simple interest on a principal over a number of years.",
  "formula": "I = P × r × t",
  "dateModified": "2026-10-03",
  "run_url": "https://www.revenuelab.fyi/api/public/calc?tool=simple-interest",
  "inputs": [
    {
      "id": "principal",
      "label": "Principal",
      "kind": "number",
      "hint": null,
      "default": 5000,
      "unit": "$",
      "min": 0,
      "max": null
    },
    {
      "id": "rate",
      "label": "Annual rate",
      "kind": "number",
      "hint": null,
      "default": 5,
      "unit": "%",
      "min": 0,
      "max": null
    },
    {
      "id": "years",
      "label": "Years",
      "kind": "number",
      "hint": null,
      "default": 3,
      "unit": null,
      "min": 0,
      "max": null
    }
  ],
  "outputs": [
    {
      "id": "interest",
      "label": "Interest",
      "format": "currency",
      "hint": null,
      "primary": true
    },
    {
      "id": "total",
      "label": "Total balance",
      "format": "currency",
      "hint": null,
      "primary": false
    }
  ],
  "worked_example": {
    "inputs": [
      "Principal: 5000 $",
      "Annual rate: 5 %",
      "Years: 3"
    ],
    "outputs": [
      "Interest: $750.00",
      "Total balance: $5,750.00"
    ]
  },
  "how_to": {
    "title": "How to use this",
    "steps": [
      "Enter principal ($).",
      "Enter annual rate (%).",
      "Enter years.",
      "Read your interest 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": 3000,
        "rate": 5,
        "years": 1.7999999999999998
      }
    },
    {
      "name": "Typical",
      "description": "Defaults — the most common real-world setup.",
      "values": {
        "principal": 5000,
        "rate": 5,
        "years": 3
      }
    },
    {
      "name": "Ambitious",
      "description": "Higher-end numbers — what if things really pop?",
      "values": {
        "principal": 8000,
        "rate": 5,
        "years": 4.800000000000001
      }
    }
  ],
  "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 simple interest calculator work?",
      "a": "Compute simple interest on a principal over a number of years. The underlying maths is: I = P × r × t"
    },
    {
      "q": "What do I need to enter?",
      "a": "3 values: principal, annual rate, and years. 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 interest 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/compound-interest",
    "https://www.revenuelab.fyi/toolbox/loan"
  ],
  "license": "CC-BY-4.0",
  "citation": "RevenueLab — Simple Interest Calculator (https://www.revenuelab.fyi/toolbox/simple-interest)"
}