Prepayment penalty calculator API

Weighs a prepayment penalty (penaltyPct of outstanding balance) against the remaining interest that would otherwise accrue, and recommends whether to prepay. Answers 'Is it worth prepaying despite the penalty?','How much does the prepayment penalty cost me?'.

Price$0.01per request

MethodPOST

Route/v1/calc/loan-prepayment-penalty

StatusLive

MIME typeapplication/json

Rate limit120/minute

CacheNo cache

loanprepaymentpenaltypayoffinterestmortgagecalculator

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

Integration docs

Example request

{
  "outstandingBalance": 50000,
  "annualRatePct": 6,
  "remainingMonths": 60,
  "penaltyPct": 2
}

Example response

{
  "penaltyAmount": 1000,
  "interestIfKept": 7998.4,
  "netSavingsFromPrepaying": 6998.4,
  "worthPrepaying": true,
  "recommendation": "Prepay — interest saved exceeds the penalty.",
  "breakdown": {
    "outstandingBalance": 50000,
    "penaltyPct": 2,
    "remainingMonths": 60,
    "monthlyPayment": 966.64
  }
}

Input schema

{
  "type": "object",
  "required": [
    "outstandingBalance",
    "annualRatePct",
    "remainingMonths",
    "penaltyPct"
  ],
  "properties": {
    "outstandingBalance": {
      "type": "number",
      "description": "Current outstanding balance.",
      "examples": [
        50000
      ]
    },
    "annualRatePct": {
      "type": "number",
      "description": "Annual nominal rate in percent.",
      "examples": [
        6
      ]
    },
    "remainingMonths": {
      "type": "number",
      "description": "Months remaining on the loan.",
      "examples": [
        60
      ]
    },
    "penaltyPct": {
      "type": "number",
      "description": "Prepayment penalty as percent of balance.",
      "examples": [
        2
      ]
    }
  }
}

Output schema

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