Full Amortization Schedule
Period-by-period payment / principal / interest / balance from loan amount, rate, and term.
Example
You enter
- Principal (loan amount, $) 320000
- APR (percent) 6.5
- Term (years) 30
You get
- Monthly P&I $2022.62
- Scheduled term (months) 360
- Total interest $408142
Details, formula, and sources
Optional extra-principal accelerates payoff. Reports total interest, total paid, months saved, and three sample rows.
Monthly P&I = (P * r) / (1 - (1 + r)^-n) where r = APR/12 and n = term in months. Per-row: interest = balance * r; principal = payment - interest + extra; balance = balance - principal; loop until balance <= 0 or n reached.
Standard mortgage amortization (closed-form annuity formula). FNMA Single-Family Selling Guide §B2-1.2 (loan term and amortization). 12 CFR §1026.18 (truth-in-lending payment schedule disclosure).
FNMA Selling Guide free at selling-guide.fanniemae.com. 12 CFR Part 1026 (Regulation Z) free at ecfr.gov.
Estimate. Lender governs final underwriting and rate / fee disclosure. Appraiser governs the appraised value. State law and the agency's program guidelines may impose stricter limits than the published thresholds.
Field names used by the API: principal, apr_percent, term_years, monthly_principal_and_interest, scheduled_term_months, total_interest
- Extra principal posting applied immediately each month before next interest accrualstandard / preferred convention
- Rounding no per-payment rounding; balance closes within $0.01 floating-point precisionconvention