Mortgage Calculator API

About the Mortgage Calculator API

Mortgage Calculator works by using the loan amount, interest rate, and loan term to calculate the monthly mortgage payment, total interest, and more.

What people use it for

Listing Affordability Estimates

Real estate portals display estimated monthly costs, factoring in local taxes and HOA dues beside listing sale prices.

Mortgage Offer Comparisons

When prospective borrowers evaluate competing quotes, financial platforms run side-by-side payment breakdowns across differing interest rates and terms.

Budget Planning Applications

To assess homeownership readiness, personal finance apps calculate prospective monthly housing obligations against user savings and down payment targets.

Client Payment Previews

Mortgage brokers quote projected monthly housing dues to prospective buyers during initial consultations before submitting formal underwriting applications.

Ways to call it

One endpoint, many ways in — REST with JSON, XML, YAML and CSV, plus GraphQL and an MCP interface for AI agents.

JSON

Default REST response

XML

Markup format

YAML

Human-readable

CSV

Tabular export

Beta

GraphQL

Query language

New

MCP

For AI agents

Request parameters — POST /v1/mortgagecalculator

Sent as JSON in the request body. Premium parameters are accepted on every plan but only take effect on plans that include them. Anything not listed here is dropped rather than passed through.

Required

Optional

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curl -X POST "https://api.apiverve.com/v1/mortgagecalculator" \
  -H "x-api-key: YOUR_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{"amount":570000,"rate":6.8,"years":30,"downpayment":1,"annual_propertytax":1,"annual_homeinsurance":1,"annual_hoa":1}'

Authentication

Send your key in the x-api-key header. That is the only auth step — no token exchange, and no per-endpoint scope to configure.

Response — POST /v1/mortgagecalculator

Every APIVerve endpoint returns the same three top-level keys, so one response handler covers your whole integration: status, error and data. Only data changes shape.

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{
  "status": "ok",
  "error": null,
  "data": {
    "amount": 570000,
    "downpayment": 0,
    "rate": 6.8,
    "years": 30,
    "total_interest_paid": 767750.49,
    "total_loan_payment": 1337750.49,
    "interestRatio": 57.39,
    "monthly_payment": {
      "total": 3715.97,
      "mortgage": 3715.97,
      "property_tax": 0,
      "hoa": 0,
      "home_insurance": 0
    },
    "annual_payment": {
      "total": 44591.68,
      "mortgage": 44591.68,
      "property_tax": 0,
      "hoa": 0,
      "home_insurance": 0
    },
    "formatted": {
      "amount": "$570,000",
      "monthlyPayment": "$3,715.97",
      "totalInterestPaid": "$767,750.49",
      "totalLoanPayment": "$1,337,750.49"
    },
    "amortization_schedule": [
      {
        "month": 1,
        "interest_payment": 3230,
        "principal_payment": 485.97,
        "remaining_balance": 569514.03
      },
      {
        "month": 2,
        "interest_payment": 3227.25,
        "principal_payment": 488.73,
        "remaining_balance": 569025.3
      },
      {
        "month": 3,
        "interest_payment": 3224.48,
        "principal_payment": 491.5,
        "remaining_balance": 568533.8
      }
    ]
  }
}

Response fields

Paths are relative to data. Premium fields are absent rather than zeroed on plans that do not include them, so check for presence instead of comparing to 0.

Response headers

Every response carries your balance, so your own code always knows where it stands without polling anything. All four are exposed to browsers through CORS.

Errors

Read the HTTP status first, then error for the specific reason. The body names the parameter that has to change.

What a call costs — 2 credits per call

Credits are shared across every APIVerve API — one balance, one key, one bill. Failed requests never count against it, so a rejected input costs nothing.

Calls are what the credits buy at this API's rate — spend them here, on any of the other APIs, or across both. Nothing is reserved per endpoint.

Zero-code embed — one snippet, no backend

Drop an interactive Mortgage Calculator form onto any page. The widget calls the API for you, so no key ever appears in your markup and there is nothing to deploy.

Changelog — Mortgage Calculator API

Every change to this endpoint, newest first. Breaking changes ship as a new version and the previous one keeps serving — response fields are added, never removed or retyped in place, so an integration written against v1 keeps working.

Currently v1