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mortgage-amortization.underscoredone.com calculate
https://mortgage-amortization.underscoredone.com/calculate
answers 402
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,
We sent a real
POST request to this endpoint and it
answered 402 with payment requirements we could parse.
- Price
- $0.01
- Network
- base
- Pay to
- 0xE9740820225B3918b4ddd1292C7cA4Ca0e2C2F08
- Spec dialect
- v2 (declares x402Version 2)
- Transport
- PAYMENT-REQUIRED header
- HTTP method
- POST
- Response latency
- 162 ms
- Payment options
- 2 usable of 2
- Last checked
- 2026-09-06T01:08:12.053Z (31d ago)
- Category
- finance-crypto
Re-check it yourself:
curl "https://api.the402.dev/validate?url=https%3A%2F%2Fmortgage-amortization.underscoredone.com%2Fcalculate"