{
  "schemaVersion": 1,
  "slug": "simple-interest-calculator",
  "category": "finance",
  "kind": "implementation",
  "independentValidation": false,
  "implementationHash": "3a3faddb3d12857d76c428f317754be87c9692f52c82e08addb2bca46031101b",
  "provenance": "Generated from the calculation contract used by the published page. Publication is not external validation.",
  "sourceFiles": [
    "data/calculators/simple-interest-calculator.json",
    "src/engine.js"
  ],
  "runtimeSource": "/sources/engine.txt",
  "runtimeHash": "5c888d8898afbdee36267bb9977829e1e2ac568f6677c8ee87469c139864645c",
  "scope": "The compute function records implemented equations, constants, lookup tables and custom rules. Inputs record defaults and allowed values; outputs record precision and units. Defaults are examples, not recommendations. General background references are not evidence for this specific algorithm.",
  "publishedFormula": {
    "formula": "I = P×r÷100×t; A = P + I; I_y = P×r÷100",
    "vars": [
      [
        "P",
        "Principal"
      ],
      [
        "r",
        "Annual interest rate (%)"
      ],
      [
        "t",
        "Years"
      ],
      [
        "I",
        "Total interest"
      ],
      [
        "A",
        "Principal plus interest"
      ],
      [
        "I_y",
        "Interest per year"
      ]
    ],
    "note": "Simple interest does not capitalise accumulated interest; currency follows the principal input."
  },
  "externalEvidence": {
    "reviewedAt": "2026-10-04",
    "sources": [
      {
        "name": "OpenStax — Simple interest",
        "url": "https://openstax.org/books/contemporary-mathematics/pages/6-3-simple-interest"
      }
    ],
    "basis": "Interest = principal × annual percent / 100 × years.",
    "limitations": "Interest is not compounded; the principal and rate stay constant.",
    "implementationHash": "3a3faddb3d12857d76c428f317754be87c9692f52c82e08addb2bca46031101b"
  },
  "contract": {
    "compute": "const interest = principal*rate/100*years; return { interest, total: principal+interest, perYear: principal*rate/100 };",
    "inputs": [
      {
        "name": "principal",
        "type": "number",
        "default": 10000,
        "min": 0,
        "max": 1000000000,
        "step": 100
      },
      {
        "name": "rate",
        "type": "number",
        "default": 5,
        "min": 0,
        "max": 100,
        "step": 0.01
      },
      {
        "name": "years",
        "type": "number",
        "default": 3,
        "min": 0,
        "max": 100,
        "step": 0.25,
        "slider": true
      }
    ],
    "outputs": [
      {
        "name": "interest",
        "precision": 2,
        "unit": "$"
      },
      {
        "name": "total",
        "precision": 2,
        "unit": "$"
      },
      {
        "name": "perYear",
        "precision": 2,
        "unit": "$"
      }
    ],
    "interpret": null
  }
}