Index onlineMerchant portal
Api Endpoint

Mortgage & Loan Amortization Cal

Give this API a loan amount, an interest rate, and a repayment term, and it returns the exact monthly payment plus a full month-by-month schedule: interest paid, principal repaid, and balance remaining for every payment. Ask what an extra $300 a month, or a $10,000 lump sum in month 24, would do and it reports the months and interest saved. Every figure uses banker's rounding at pinned precision, so two correct systems agree to the cent. You supply the rate; the API does the math.

Open interactive test console

Offering

Provider
mortgage-amortization.underscoredone.com
Method
POST
Offering type
Api Endpoint
Transport type
http
Category
Financial Analysis
Delivery
Not provided
Pricing model
Not provided
x402 version
2

Endpoint context

URL
https://mortgage-amortization.underscoredone.com/calculate
MIME type
application/json
First seen
2026-10-16T01:50:10.647Z
Last seen
Tags
mortgage calculator, loan amortization, amortization schedule, mortgage, monthly payment calculator

Website

Payment pricing

x402 payment terms are the authoritative price for calling this endpoint.

Payment option 1
0.01 USDC
Atomic price: 10000 · Network: eip155:8453 · Asset: USDC · Scheme: exact
Payment option 2
0.01 USDC
Atomic price: 10000 · Network: solana:5eykt4UsFv8P8NJdTREpY1vzqKqZKvdp · Asset: USDC · Scheme: exact
Raw x402 terms
[
  {
    "scheme": "exact",
    "network": "eip155:8453",
    "asset": "0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913",
    "amount": "10000",
    "payTo": "0xE9740820225B3918b4ddd1292C7cA4Ca0e2C2F08"
  },
  {
    "scheme": "exact",
    "network": "solana:5eykt4UsFv8P8NJdTREpY1vzqKqZKvdp",
    "asset": "EPjFWdd5AufqSSqeM2qN1xzybapC8G4wEGGkZwyTDt1v",
    "amount": "10000",
    "payTo": "8ugAWAXDB8V18kiUrGZTq1oMvU3C6Fxs8hfC6rvzQT3b"
  }
]

Observed health

Status
Reachable
Latest latency
673 ms
Average latency
223 ms
HTTP status
405
Last checked
Reachability
100% over 5 checks

Latency is measured to the first response headers. A reachable result does not verify response accuracy or merchant identity.

Input schema

{
  "type": "object",
  "properties": {
    "type": {
      "type": "string",
      "const": "http"
    },
    "method": {
      "type": "string",
      "enum": [
        "POST",
        "PUT",
        "PATCH"
      ]
    },
    "bodyType": {
      "type": "string",
      "enum": [
        "json",
        "form-data",
        "text"
      ]
    },
    "body": {
      "type": "object",
      "properties": {
        "principal": {
          "type": "number",
          "description": "Amount borrowed, in dollars. Must be greater than zero."
        },
        "annual_rate_percent": {
          "type": "number",
          "description": "Yearly interest rate as a percentage - send 6.5 for 6.5%. Use 0 for an interest-free loan."
        },
        "term_months": {
          "type": "integer",
          "description": "Number of monthly payments. 360 for a 30-year mortgage. Minimum 1."
        },
        "start_date": {
          "type": "string",
          "description": "Date of the first payment, YYYY-MM-DD."
        },
        "extra_monthly_payment": {
          "type": "number",
          "description": "Optional extra principal paid every month. Defaults to 0."
        },
        "one_time_payments": {
          "type": "array",
          "description": "Optional lump-sum principal payments; each item needs 'month' and 'amount'."
        },
        "summary_only": {
          "type": "boolean",
          "description": "Set true to return totals only, without the row-by-row schedule."
        },
        "rounding": {
          "type": "integer",
          "description": "Decimal places for money values, 2 to 6. Defaults to 2."
        }
      },
      "required": [
        "principal",
        "annual_rate_percent",
        "term_months",
        "start_date"
      ],
      "additionalProperties": false
    }
  },
  "required": [
    "type",
    "method",
    "bodyType",
    "body"
  ],
  "additionalProperties": false
}

Output schema

{
  "type": "object",
  "properties": {
    "type": {
      "type": "string"
    },
    "example": {
      "type": "object",
      "properties": {
        "api_version": {
          "type": "string"
        },
        "inputs_echo": {
          "type": "object",
          "additionalProperties": true
        },
        "rounding": {
          "type": "object",
          "additionalProperties": true
        },
        "scheduled_payment": {
          "type": "number"
        },
        "summary": {
          "type": "object",
          "additionalProperties": true
        },
        "with_extra_payments": {
          "type": "object",
          "additionalProperties": true
        },
        "schedule": {
          "type": "array",
          "items": {
            "type": "object"
          }
        }
      },
      "required": [
        "api_version",
        "inputs_echo",
        "rounding",
        "scheduled_payment",
        "summary",
        "with_extra_payments",
        "schedule"
      ]
    }
  },
  "required": [
    "type"
  ]
}