---
title: "Amortizing and interest-only payment math for a commercial loan: monthly and annual debt service, total interest over..."
method: POST
path: "/api/v1/tools/calculate_payment"
tags: ["Calculators"]
---

# Amortizing and interest-only payment math for a commercial loan: monthly and annual debt service, total interest over...

`POST /api/v1/tools/calculate_payment`

## Request

- Base URL: `https://relendi.com`
- URL: `https://relendi.com/api/v1/tools/calculate_payment`
- Auth: none declared

Amortizing and interest-only payment math for a commercial loan: monthly and annual debt service, total interest over the term, and the balloon balance at maturity when the term is shorter than the amortization (the normal CRE case — a 10-year term on a 30-year schedule).

## Request body

- object
  - `loanAmount` number, required
  - `rate` number, required: DECIMAL (0.0725 = 7.25%)
  - `amortizationYears` integer
  - `termYears` number: Balloon at this point
  - `interestOnly` boolean

## Response `200`

The computed result.

- object
  - `tool` 'calculate_payment', required
  - `deterministic` boolean
  - `result` object, required: Result fields: monthlyPayment, annualDebtService, interestOnly, amortizationYears, termYears, totalInterestOverTerm, balloonBalance, totalPaidOverTerm, note.

## Other responses

- `400`: Error. Possible codes: invalid_input.
- `404`: Error. Possible codes: unknown_tool, not_found.
- `405`: Error. Possible codes: method_not_allowed.
- `429`: Error. Possible codes: rate_limited, quota_exhausted.
- `500`: Error. Possible codes: tool_error.
- `503`: Error. Possible codes: flag_off.

---

[API](https://skmtc.dev/relendi/apis/relendi-public-api.md) · [All operations](https://skmtc.dev/relendi/apis/relendi-public-api/llms.txt) · [OpenAPI document](https://skmtc.dev/relendi/apis/relendi-public-api/revisions/7e4b30838121?raw)