Mortgage Calculator

Calculate monthly mortgage payments and generate a full amortization schedule for any fixed-rate loan. Returns the monthly payment, total cost, total interest, and a month-by-month breakdown.

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Overview

Use Cases

Mortgage calculators for real estate platforms
Loan comparison tools
Personal finance dashboards
Amortization schedule exports for borrowers
Financial planning and budgeting apps

Features

Standard fixed-rate amortization formula

Full month-by-month schedule (principal, interest, balance per payment)

Summary fields — monthly payment, total payment, total interest

Supports loan terms from 1 to 50 years

Any principal and annual interest rate

API Endpoints

Calculate Mortgage

Returns the monthly payment, total cost, and full amortization schedule for a fixed-rate mortgage.

GET

https://api.requiems.xyz/v1/finance/mortgage

Parameters

Name	Type	Required	Description
principal	`number`	Required	Loan amount in your chosen currency (e.g. 300000 for $300,000)
rate	`number`	Required	Annual interest rate as a percentage (e.g. 6.5 for 6.5%). Must be greater than 0.
years	`integer`	Required	Loan term in years (1–50)

Try it out

Live Demo

Request

principal * (number)

Loan amount in your chosen currency (e.g. 300000 for $300,000)

rate * (number)

Annual interest rate as a percentage (e.g. 6.5 for 6.5%). Must be greater than 0.

years * (integer)

Loan term in years (1–50)

Response Fields

Field	Type	Description
principal	`number`	The original loan amount passed in the request
rate	`number`	The annual interest rate passed in the request
years	`integer`	The loan term in years passed in the request
monthly_payment	`number`	Fixed monthly payment amount (rounded to 2 decimal places)
total_payment	`number`	Total amount paid over the life of the loan
total_interest	`number`	Total interest paid (total_payment minus principal)
schedule	`array`	Full amortization schedule — one entry per month (years × 12 entries)
schedule[].month	`integer`	Month number (1 to years × 12)
schedule[].payment	`number`	Total payment for this month
schedule[].principal	`number`	Portion of this month's payment applied to principal
schedule[].interest	`number`	Portion of this month's payment applied to interest
schedule[].balance	`number`	Remaining loan balance after this payment

Code Examples

curl "https://api.requiems.xyz/v1/finance/mortgage?principal=300000&rate=6.5&years=30" \
  -H "requiems-api-key: YOUR_API_KEY"

import requests

url = "https://api.requiems.xyz/v1/finance/mortgage"
headers = {"requiems-api-key": "YOUR_API_KEY"}
params = {"principal": 300000, "rate": 6.5, "years": 30}

response = requests.get(url, headers=headers, params=params)
data = response.json()["data"]
print(data["monthly_payment"])  # 1896.2
print(data["total_interest"])   # 382632.0
print(len(data["schedule"]))    # 360

const params = new URLSearchParams({ principal: 300000, rate: 6.5, years: 30 });
const response = await fetch(
  `https://api.requiems.xyz/v1/finance/mortgage?${params}`,
  { headers: { 'requiems-api-key': 'YOUR_API_KEY' } }
);

const { data } = await response.json();
console.log(data.monthly_payment);  // 1896.2
console.log(data.total_interest);   // 382632.0
console.log(data.schedule.length);  // 360

require 'net/http'
require 'json'

uri = URI('https://api.requiems.xyz/v1/finance/mortgage')
uri.query = URI.encode_www_form(principal: 300000, rate: 6.5, years: 30)

request = Net::HTTP::Get.new(uri)
request['requiems-api-key'] = 'YOUR_API_KEY'

response = Net::HTTP.start(uri.hostname, uri.port, use_ssl: true) do |http|
  http.request(request)
end

data = JSON.parse(response.body)['data']
puts data['monthly_payment']  # 1896.2
puts data['total_interest']   # 382632.0

Error Responses

bad_request

A required parameter is missing, not a valid number, or out of range (e.g. years > 50 or rate <= 0).

internal_error

Unexpected server error.

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