Loan payment calculator API

Computes the fully-amortizing monthly payment via M = P*r/(1-(1+r)^-n) and returns total paid, total interest, and an interest-vs-principal breakdown. Answers 'What is the monthly payment on this loan?','How much total interest will I pay?'.

Price$0.01per request

MethodPOST

Route/v1/calc/loan-payment

StatusLive

MIME typeapplication/json

Rate limit120/minute

CacheNo cache

loanamortizationmortgagepaymentinterestfinancecalculator

API URLhttps://x402.hexl.dev/v1/calc/loan-payment

Integration docs

Example request

{
  "principal": 250000,
  "annualRatePct": 6.5,
  "termMonths": 360
}

Example response

{
  "monthlyPayment": 1580.17,
  "totalPaid": 568861.22,
  "totalInterest": 318861.22,
  "principal": 250000,
  "termMonths": 360,
  "annualRatePct": 6.5,
  "formula": "M = P*r/(1-(1+r)^-n), r = monthly rate",
  "breakdown": {
    "principal": 250000,
    "interest": 318861.22,
    "interestShareOfPayments": 0.5605
  }
}

Input schema

{
  "type": "object",
  "required": [
    "principal",
    "annualRatePct",
    "termMonths"
  ],
  "properties": {
    "principal": {
      "type": "number",
      "description": "Loan principal in currency units.",
      "examples": [
        250000
      ]
    },
    "annualRatePct": {
      "type": "number",
      "description": "Annual nominal interest rate in percent.",
      "examples": [
        6.5
      ]
    },
    "termMonths": {
      "type": "number",
      "description": "Term in months.",
      "examples": [
        360
      ]
    }
  }
}

Output schema

{
  "type": "object",
  "additionalProperties": true
}