Mortgage Calculator

Overview

A mortgage API and payment calculation API for real estate listings, lending tools and budgeting apps. Mortgage Calculator works by using the loan amount, interest rate, and loan term to calculate the monthly mortgage payment and loan-to-value ratio, with total interest paid, PMI and its removal date, payoff dates and extra-payment payoff scenarios on paid plans.

Live Test Mortgage Calculator API →

Endpoint

One host, one path per API. The block below shows this call in four languages; every one of them is the same HTTP request. Making requests covers the timeouts, retries and parameter rules that apply to all of them. The SDKs wrap the same call in a typed client.

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curl -X POST https://api.apiverve.com/v1/mortgagecalculator \
  -H "x-api-key: your_api_key_here" \
  -H "Content-Type: application/json" \
  -d '{
  "amount": 570000,
  "rate": 6.8,
  "years": 30,
  "downpayment": 57000,
  "pmi_rate": 0.5,
  "extra_monthly": 200,
  "start_date": "2026-11-01"
}'

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const res = await fetch('https://api.apiverve.com/v1/mortgagecalculator', {
  method: 'POST',
  headers: {
    'x-api-key': 'your_api_key_here',
    'Content-Type': 'application/json',
  },
  body: JSON.stringify({
  "amount": 570000,
  "rate": 6.8,
  "years": 30,
  "downpayment": 57000,
  "pmi_rate": 0.5,
  "extra_monthly": 200,
  "start_date": "2026-11-01"
}),
});

if (!res.ok) throw new Error(`${res.status} ${await res.text()}`);

const { data } = await res.json();
console.log(data);

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import requests

res = requests.post(
    "https://api.apiverve.com/v1/mortgagecalculator",
    headers={"x-api-key": "your_api_key_here"},
    json={
    "amount": 570000,
    "rate": 6.8,
    "years": 30,
    "downpayment": 57000,
    "pmi_rate": 0.5,
    "extra_monthly": 200,
    "start_date": "2026-11-01"
},
    timeout=15,
)
res.raise_for_status()

print(res.json()["data"])

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package main

import (
	"fmt"
	"io"
	"net/http"
	"strings"
)

func main() {
	body := strings.NewReader(`{
  "amount": 570000,
  "rate": 6.8,
  "years": 30,
  "downpayment": 57000,
  "pmi_rate": 0.5,
  "extra_monthly": 200,
  "start_date": "2026-11-01"
}`)
	req, _ := http.NewRequest("POST", "https://api.apiverve.com/v1/mortgagecalculator", body)
	req.Header.Set("Content-Type", "application/json")
	req.Header.Set("x-api-key", "your_api_key_here")

	res, err := http.DefaultClient.Do(req)
	if err != nil {
		panic(err)
	}
	defer res.Body.Close()

	out, _ := io.ReadAll(res.Body)
	fmt.Println(string(out))
}

Replace your_api_key_here with the key from your dashboard. When the inputs arrive as a list rather than one at a time, batch requests run up to 200 of them through this same API in a single call.

Authentication

Send your key in the x-api-key header. That is the only auth step — there is no token exchange and no per-endpoint scope to configure. Authentication covers creating, rotating and revoking keys.

Parameters

Sent as JSON in the request body. Premium parameters are accepted on every plan but only take effect on plans that include them.

Response

Every API returns the same three top-level keys, so one response handler covers your whole integration: status, error and data. Only data changes shape. Response format covers the envelope, the other output formats and how premium fields are withheld.

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{
  "status": "ok",
  "error": null,
  "data": {
    "amount": 570000,
    "downpayment": 57000,
    "rate": 6.8,
    "years": 30,
    "total_interest_paid": 690975.44,
    "total_loan_payment": 1203975.44,
    "interestRatio": 57.39,
    "monthly_payment": {
      "total": 3558.13,
      "mortgage": 3344.38,
      "property_tax": 0,
      "hoa": 0,
      "home_insurance": 0,
      "pmi": 213.75
    },
    "annual_payment": {
      "total": 42697.51,
      "mortgage": 40132.51,
      "property_tax": 0,
      "hoa": 0,
      "home_insurance": 0,
      "pmi": 2565
    },
    "formatted": {
      "amount": "$570,000",
      "monthlyPayment": "$3,344.38",
      "totalInterestPaid": "$690,975.44",
      "totalLoanPayment": "$1,203,975.44"
    },
    "loan_amount": 513000,
    "ltv": 90,
    "payoff_date": "2056-11",
    "pmi": {
      "required": true,
      "rate": 0.5,
      "monthly": 213.75,
      "months_charged": 113,
      "removal_month": 114,
      "total": 24153.75,
      "removal_date": "2036-05"
    },
    "extra_payments": {
      "monthly": 200,
      "months_to_payoff": 304,
      "months_saved": 56,
      "total_interest_paid": 563208.85,
      "interest_saved": 127766.58,
      "payoff_date": "2052-03"
    },
    "amortization_schedule": [
      {
        "month": 1,
        "interest_payment": 2907,
        "principal_payment": 437.38,
        "remaining_balance": 512562.62,
        "date": "2026-12"
      },
      {
        "month": 2,
        "interest_payment": 2904.52,
        "principal_payment": 439.85,
        "remaining_balance": 512122.77,
        "date": "2027-01"
      },
      {
        "month": 3,
        "interest_payment": 2902.03,
        "principal_payment": 442.35,
        "remaining_balance": 511680.42,
        "date": "2027-02"
      }
    ]
  }
}

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.

Errors

Read the HTTP status first, then error for the specific reason. The body names the parameter that has to change. Error handling covers the full status list and which of them are worth retrying.

Start from a template

A working app built on this API, ready to deploy with your own key. Vercel asks for the key when you deploy; the code is on GitHub to change first.

Mortgage Calculator

A full monthly mortgage payment with tax, insurance and HOA, and a breakdown of where it goes.

• Next.js
• TypeScript

Deploy to VercelSee the template →

Use cases

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.

Other ways to use Mortgage Calculator

Set up Mortgage Calculator on APIVerve, or reach the same source a different way. Your APIVerve account and credits work on all of them — one key, one balance.

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