Mortgage calculator API. Payments and amortization in one call.
Pass principal, interest rate, and loan term. Get monthly payment, total interest, and a full month-by-month amortization schedule — in structured JSON.
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What the Mortgage Calculator API Does
One endpoint. Monthly payment, total cost, total interest, and a full amortization schedule for any fixed-rate loan.
Structured output
Every response includes the fixed monthly payment, total amount paid over the life of the loan, total interest, and a schedule array with one entry per month — principal paid, interest paid, and remaining balance.
{
"monthly_payment": 1896.20,
"total_payment": 682632.00,
"total_interest": 382632.00,
"schedule": [
{ "month": 1, "payment": 1896.20,
"principal": 271.20, "interest": 1625.00,
"balance": 299728.80 }
]
}
Simple to integrate
Three query parameters: principal, rate, and years. No SDK, no configuration. A single GET request returns everything a mortgage calculator or financial planning tool needs.
GET /v1/finance/mortgage?principal=300000&rate=6.5&years=30
Host: requiems.xyz
requiems-api-key: YOUR_API_KEY
Build Mortgage Tools in Any Stack
From real estate platforms to personal finance apps — any product that deals with loans can use the Mortgage Calculator API.
Embed a mortgage calculator on property listings
Let buyers estimate monthly payments directly on listing pages. Pass the asking price as principal, pre-fill a market rate, and render the result inline.
Power loan comparison tools
Compare multiple loan offers side by side using the batch endpoint. Different principal, rate, and term combinations returned in a single API call.
Build budget planners with real amortization data
Use the month-by-month schedule to show users exactly how much of each payment goes to principal vs. interest over the full loan term.
Generate amortization schedules for borrowers
Produce PDF-ready amortization tables by iterating over the schedule array. Each entry has month, payment, principal, interest, and remaining balance.
Teach mortgage math interactively
Give students a real API to explore how rate changes or extra years affect total interest — without building the formula themselves.
Add financial modeling to your platform
Integrate mortgage calculations into CRM, ERP, or financial planning tools via a single authenticated API call — no custom math logic required.
Use together with complementary APIs.
Mortgage Calculator works even better when paired with other Requiems APIs.
Benefit: Layer CPI inflation rates on top of amortization data.
Outcome: Show borrowers the real purchasing-power cost of their loan adjusted for expected inflation in their country.
Benefit: Convert monthly payment amounts to the borrower's local currency.
Outcome: Display mortgage costs in multiple currencies for international buyers or cross-border lending platforms.
Benefit: Generate realistic borrower profiles paired with sample mortgage scenarios.
Outcome: Populate demo environments and test datasets with plausible names, addresses, and loan parameters in one pass.
Frequently Asked Questions
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Add mortgage calculations to your product with Requiems.
One API key. Mortgage calculator, inflation rates, currency exchange, and 50+ other financial APIs.