Loan Amortization Schedule
Full loan amortization: the exact monthly payment, a year-by-year principal/interest/balance table, total interest, and the effect of extra monthly payments — payoff months saved and interest saved. Deterministic mortgage math agents can quote line by line.
Worked examples
300k @ 4.5% / 30y
GET /api/v1/finance/amortization-schedule?principal=300000&annualRate=4.5&years=30
Result: 1,520.06/mo · paid off in 360 months (30.0 yrs)
…with $100/mo extra
GET /api/v1/finance/amortization-schedule?principal=300000&annualRate=4.5&years=30&extraMonthly=100
Result: 1,520.06/mo + 100 extra · paid off in 317 months (26.4 yrs)
20k @ 7% / 5y (car)
GET /api/v1/finance/amortization-schedule?principal=20000&annualRate=7&years=5
Result: 396.02/mo · paid off in 61 months (5.1 yrs)
Machine API (x402)
$0.003 / callThis tool is also a JSON API for AI agents. Requests without payment receive 402 Payment Required plus instructions; agents pay USDC on Base via the x402 protocol — no accounts, no API keys.
GET /api/v1/finance/amortization-schedule?principal=300000&annualRate=4.5&years=30 HTTP/1.1
Host: agentstoolshub.com
→ 402 (payment required, instructions in headers)
→ 200 (after X-PAYMENT header; JSON body below)
{
"tool": "finance/amortization-schedule",
"input": {"principal":300000,"annualRate":4.5,"years":30},
"result": { "value": 1520.055929, "answer": "1,520.06/mo · paid off in 360 months (30.0 yrs)" }
}Agent docs: /llms.txt · OpenAPI spec · integration guide
About this tool
The full amortization picture: exact payment, year-by-year principal vs interest split, running balance, and the concrete savings from extra monthly payments. Same closed-form payment as standard mortgage math, then a true month-by-month simulation — including final partial months.
payment = P·i/(1 − (1+i)^−n), i = rate/1200, n = months
Frequently asked questions
Why does the early schedule look all-interest?
Interest accrues on the outstanding balance, so it dominates early years. The yearly table shows the crossover point — useful when weighing extra payments.
How are extra payments applied?
Fully to principal each month (no re-amortization), which is why they shorten the term rather than lower the payment. The tool reports months and interest saved versus the plain schedule.