Balloon payment calculator API

Computes the lump-sum balloon owed when a loan amortized over a long schedule is settled early, via B_k = P*(1+r)^k - M*((1+r)^k-1)/r. Answers 'What is my balloon payment?','How much is left after the balloon term?'.

Price$0.01per request

MethodPOST

Route/v1/calc/loan-balloon-payment

StatusLive

MIME typeapplication/json

Rate limit120/minute

CacheNo cache

loanballoonamortizationmortgagecommercialinterestcalculator

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

Integration docs

Example request

{
  "principal": 200000,
  "annualRatePct": 5,
  "amortizationMonths": 360,
  "balloonAtMonth": 84
}

Example response

{
  "monthlyPayment": 1073.64,
  "balloonPayment": 175890.03,
  "balloonAtMonth": 84,
  "totalOfPayments": 266075.79,
  "interestPaid": 66075.79,
  "formula": "B_k = P*(1+r)^k - M*((1+r)^k - 1)/r",
  "breakdown": {
    "principal": 200000,
    "payment": 1073.64,
    "paymentsBeforeBalloon": 84
  }
}

Input schema

{
  "type": "object",
  "required": [
    "principal",
    "annualRatePct",
    "amortizationMonths",
    "balloonAtMonth"
  ],
  "properties": {
    "principal": {
      "type": "number",
      "description": "Loan principal.",
      "examples": [
        200000
      ]
    },
    "annualRatePct": {
      "type": "number",
      "description": "Annual nominal rate in percent.",
      "examples": [
        5
      ]
    },
    "amortizationMonths": {
      "type": "number",
      "description": "Amortization schedule length in months.",
      "examples": [
        360
      ]
    },
    "balloonAtMonth": {
      "type": "number",
      "description": "Month at which the balloon is due (< amortizationMonths).",
      "examples": [
        84
      ]
    }
  }
}

Output schema

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