My first amortization export shocked me: $17,268 paid in year 1 on a $240,000/6% loan, balance down just $2,945 — pulled from the mortgage calculator CSV in Sept 2026. It looks broken; it is front-loaded by design. This guide explains mortgage amortization schedules: how each payment splits, why the split flips over time, and how to read the schedule to time overpayments, refinances and PMI exits. (Same front-load hits Rs 60L/9% Indian EMIs — see the India guide.)
Part of the mortgage calculator guide. Generate your schedule in the mortgage calculator (yearly tables + CSV export); model extra payments in the overpayment calculator.
For informational purposes only — not financial advice. Estimates may vary; consult a qualified financial advisor for decisions. See /terms.
How each payment splits (the $240k/6% lens)
Month 1: $1,439 payment = ~$1,200 interest + ~$239 principal. Interest = 0.005 × $240,000; principal = the rest. Month 2: interest on $239,761 — slightly less, principal slightly more. That recursion, 360 times, is the schedule. Year 1: ~$14,300 interest, ~$3,000 principal. Year 15: roughly even. Final year: nearly all principal. The payment never changes (fixed-rate); only the ratio moves. Rule of thumb: in year N of 30, roughly (30−N)/30 of payment still goes to interest — coarse but directionally right.
How to read the schedule like a strategist
| Question | Read this column | Decision it drives |
|---|---|---|
| When does principal dominate? | Principal vs interest by year | Overpay hardest before the flip (~year 15) |
| When do I hit 20% equity? | Remaining balance vs value | PMI cancellation timing |
| Total cost of waiting? | Cumulative interest | Refinance vs overpay comparison |
| Payoff date? | Final row | Retirement and tenure planning |
- CSV export: download the yearly table from the calculator and chart cumulative interest — the curve's early steepness is the visual case for overpaying now, per overpayment guide.
- ARM warning: schedules assume fixed rates. Adjustable-rate resets rewrite every future row — never plan 10 years off an ARM's teaser schedule.
- Biweekly effect: extra-payment rows compress the whole table upward — payoff dates jump years on modest additions.
What extra payments look like inside the table
One $10,000 lump at month 12 of the example loan deletes roughly 30 future payments' worth of interest-small-principal rows and pulls every subsequent row upward — payoff jumps over a year closer. The visual to internalize: extra dollars do not shorten the table from the end like cutting chapters; they compress the whole table, because each dollar skips interest in every month after it lands. That is why $10,000 in year 1 outweighs $10,000 in year 20 by roughly 5× in interest saved. See exact compressions for your loan in the overpayment calculator, and the monthly automation version in extra payments guide.
Three milestones hidden in your schedule
- PMI exit (~20% equity): on 10%-down loans, extra early principal can pull PMI cancellation years forward — often worth more than the interest saved. Strategy in down payment & PMI guide.
- The flip (~year 12–15): payments turn principal-majority. Overpayments after the flip earn less — front-load extra cash early.
- Break-even vs refinance: compare remaining interest on your schedule against a new loan's total cost plus closing — method in refinance guide.
Rates and examples as of Sept 2026, illustrative only — not a lender offer. Excludes taxes, insurance, PMI, HOA, fees and ARM resets.
ARM schedules: why teaser tables lie
Every schedule above assumes fixed rates. Adjustable-rate mortgages print deceptively calm 5–7 year tables, then reset — and every row after reset is fiction until the index moves. A 5/1 ARM at 5.5% teaser amortizes beautifully for 60 months; at reset to 7.5% (within typical caps), the payment jumps ~20% and the remaining schedule rewrites entirely. Planning a decade off teaser rows is how payment shock happens: budget the reset scenario (rate + caps maximum) from day one, keep refinance eligibility intact (credit, equity, income documented), and set calendar alerts 12 months before reset to act early. If the worst-case reset payment breaks the 28% rule, the ARM was unaffordable at purchase — no matter how pretty years 1–5 looked.
For informational purposes only — not financial advice. Estimates may vary; consult a qualified financial advisor for decisions. See /terms.