Loan Calculator API

Fixed-rate loan or mortgage repayment: monthly payment, total interest, total repaid, a yearly amortisation summary and optionally the full monthly schedule.

POST /api/v1/tools/loan-calculatorMCP loan_calculatorCalculators

Calculate the monthly repayment, total interest and total cost of a fixed-rate loan or mortgage, with a yearly amortisation table and CSV export.

Input

Send these as a JSON object. Unknown fields are rejected.

amount: Amount borrowed. (number, 0 to …, required)
rate: Annual interest rate in percent, e.g. 6 for 6%. Interest is charged monthly at rate ÷ 12. (number, 0 to 100, required)
term: Loan term in termUnit; must come to a whole number of months, at most 600. (number, 0 to …, required)
termUnit: years or months. (string, one of years, months, default "years")
schedule: Include the month-by-month schedule (payment, principal, interest, balance). (boolean, default false)

Try it in the browser JSON Schema Get an API key

curl https://pithlab.com/api/v1/tools/loan-calculator \n  -H "Authorization: Bearer $PITHLAB_KEY" \n  -H "Content-Type: application/json" \n  -d '{"amount":200000,"rate":6,"term":30,"termUnit":"years"}'

Example response

{
  "ok": true,
  "result": {
    "monthlyPayment": 1199.1010503055138,
    "months": 360,
    "totalPaid": 431676.3781099775,
    "totalInterest": 231676.37810997642,
    "yearly": [
      {
        "year": 1,
        "principal": 2456.023424553548,
        "interest": 11933.189179112618,
        "balance": 197543.97657544646
      },
      {
        "year": 2,
        "principal": 2607.5055752679655,
        "interest": 11781.707028398201,
        "balance": 194936.47100017848
      },
      {
        "year": 3,
        "principal": 2768.3308135749776,
        "interest": 11620.881790091187,
        "balance": 192168.14018660353
      },
      {
        "year": 4,
        "principal": 2939.0754006733514,
        "interest": 11450.137202992815,
        "balance": 189229.06478593018
      },
      {
        "year": 5,
        "principal": 3120.3511402916597,
        "interest": 11268.861463374506,
        "balance": 186108.71364563858
      },
      {
        "year": 6,
        "principal": 3312.8075708737433,
        "interest": 11076.405032792423,
        "balance": 182795.90607476485
      },
      {
        "year": 7,
        "principal": 3517.1342929733823,
        "interest": 10872.078310692785,
        "balance": 179278.77178179147
      },
      {
        "year": 8,
        "principal": 3734.063440197574,
        "interest": 10655.149163468592,
        "balance": 175544.7083415939
      },
      {
        "year": 9,
        "principal": 3964.372302552185,
        "interest": 10424.840301113982,
        "balance": 171580.33603904172
      },
      {
        "year": 10,
        "principal": 4208.886111589831,
        "interest": 10180.326492076336,
        "balance": 167371.44992745193
      },
      {
        "year": 11,
        "principal": 4468.480997339572,
        "interest": 9920.731606326595,
        "balance": 162902.96893011234
      },
      {
        "year": 12,
        "principal": 4744.087127613573,
        "interest": 9645.125476052592,
        "balance": 158158.88180249877
      },
      {
        "year": 13,
        "principal": 5036.692040939319,
        "interest": 9352.520562726848,
        "balance": 153122.18976155948
      },
      {
        "year": 14,
        "principal": 5347.344185059795,
        "interest": 9041.868418606371,
        "balance": 147774.84557649968
      },
      {
        "year": 15,
        "principal": 5677.15667368064,
        "interest": 8712.055929985527,
        "balance": 142097.68890281903
      },
      {
        "year": 16,
        "principal": 6027.3112749252,
        "interest": 8361.901328740965,
        "balance": 136070.3776278939
      },
      {
        "year": 17,
        "principal": 6399.06264578881,
        "interest": 7990.1499578773555,
        "balance": 129671.31498210509
      },
      {
        "year": 18,
        "principal": 6793.74282776492,
        "interest": 7595.469775901246,
        "balance": 122877.57215434017
      },
      {
        "year": 19,
        "principal": 7212.766019751597,
        "interest": 7176.446583914568,
        "balance": 115664.8061345886
      },
      {
        "year": 20,
        "principal": 7657.633645340491,
        "interest": 6731.578958325673,
        "balance": 108007.17248924809
      },
      {
        "year": 21,
        "principal": 8129.939732645066,
        "interest": 6259.272871021099,
        "balance": 99877.23275660301
      },
      {
        "year": 22,
        "principal": 8631.37662594487,
        "interest": 5757.835977721297,
        "balance": 91245.85613065813
      },
      {
        "year": 23,
        "principal": 9163.741049611535,
        "interest": 5225.4715540546285,
        "balance": 82082.11508104658
      },
      {
        "year": 24,
        "principal": 9728.940546044469,
        "interest": 4660.272057621696,
        "balance": 72353.17453500211
      },
      {
        "year": 25,
        "principal": 10329.000310684301,
        "interest": 4060.212292981864,
        "balance": 62024.174224317794
      },
      {
        "year": 26,
        "principal": 10966.070448595048,
        "interest": 3423.142155071119,
        "balance": 51058.10377572274
      },
      {
        "year": 27,
        "principal": 11642.43367861634,
        "interest": 2746.7789250498254,
        "balance": 39415.6700971064
      },
      {
        "year": 28,
        "principal": 12360.513512690952,
        "interest": 2028.6990909752128,
        "balance": 27055.15658441544
      },
      {
        "year": 29,
        "principal": 13122.88293967531,
        "interest": 1266.3296639908551,
        "balance": 13932.27364474013
      },
      {
        "year": 30,
        "principal": 13932.273644740128,
        "interest": 456.9389589177103,
        "balance": 0
      }
    ],
    "text": "Monthly payment 1,199.10 for 360 months: total interest 231,676.38, total repaid 431,676.38"
  }
}