Mortgage Amortization Table
Generate a full mortgage amortization schedule with charts and summary
关于此工具
Enter your loan amount, interest rate, loan term, and start date to generate a complete payment-by-payment amortization schedule. Each row shows the payment number, payment date, principal paid, interest paid, total payment, and remaining balance. The summary section displays total interest paid over the life of the loan, total amount paid, and the projected payoff date. Two SVG charts visualise the data: a remaining-balance curve showing equity growth over time, and a stacked principal-vs-interest bar chart revealing how the payment split shifts as the loan matures. Export the full table as a CSV for use in a spreadsheet.
使用方法
- 1 Enter the loan amount (principal).
- 2 Enter the annual interest rate as a percentage (e.g. 6.5).
- 3 Set the loan term in years.
- 4 Choose the loan start date — this determines payment dates in the schedule.
- 5 Click 'Generate Schedule' to build the full amortization table.
- 6 Review the summary for total interest, total paid, and payoff date.
- 7 Scroll through the payment table or click 'Export CSV' to download it.
What amortization really means for your loan
A fixed-rate mortgage is paid off with the same payment every month, yet the split between interest and principal inside that payment shifts dramatically over time. Amortization is the schedule that reveals this split, payment by payment. Early on, you owe interest on a large balance, so most of your payment is interest and only a sliver reduces what you owe. As the balance shrinks, the interest portion shrinks with it and more of each payment goes to principal — which is why a mortgage seems to make almost no dent for years and then collapses quickly near the end. This tool generates the full schedule, charts it, and lets you export it.
The formula behind the monthly payment
The fixed payment comes from the standard amortization formula:
M = P × r(1+r)ⁿ / ((1+r)ⁿ − 1)
where P is the loan amount, r is the monthly interest rate (the annual rate divided by 12), and n is the total number of monthly payments (years × 12). Each month, the tool then computes interest as balance × r, treats the rest of the payment (M − interest) as principal, and subtracts that principal from the balance before the next month repeats. If you ever enter a 0% rate, the math degenerates cleanly to P ÷ n — an equal-principal split with no interest.
A worked example you can verify
Take the tool's defaults: $300,000 at 6.5% for 30 years.
- Monthly rate
r = 0.065 ÷ 12 = 0.0054167; paymentsn = 360. - Plugging into the formula gives a monthly payment of about $1,896.20.
- Month 1: interest = $300,000 × 0.0054167 = $1,625.00; principal = $1,896.20 − $1,625.00 = $271.20. Balance drops to $299,728.80.
- Month 2: interest is now charged on the slightly smaller balance, so it dips to about $1,623.53 and a touch more goes to principal.
Over the full 360 payments you pay roughly $382,600 in interest — more than the loan itself. The summary cards surface exactly these numbers: monthly payment, total interest, total paid, and the projected payoff date.
Reading the two charts
The remaining-balance chart is a curve, not a straight line. It starts nearly flat — proof of how little principal you retire early — then bends steeply downward in the final years as principal payments dominate. The principal-vs-interest chart stacks the two components per year: tall red interest bars at the start that shrink every year, with green principal bars growing to take their place. Seeing the crossover point — the year where principal finally exceeds interest in each payment — is the single most useful insight an amortization schedule offers.
Practical uses
- Comparing loan terms. Run 30 years, then 15 years. The 15-year payment is higher, but the total-interest figure is often less than half. The schedule makes that trade-off concrete.
- Seeing the cost of rate differences. Re-run at 6.0% versus 6.5% to watch how a half-point changes both the monthly payment and the lifetime interest.
- Planning around the payoff date. The start-date field places real calendar months on every row, so you can see precisely which month the loan ends.
- Exporting for your records. The CSV export drops the whole table into a spreadsheet where you can add extra-payment columns of your own.
Common misunderstandings
- "My payment is mostly principal." Not at first. On a fresh 30-year loan at typical rates, over 85% of the first payment is interest. Check month 1 in the table.
- "A lower monthly payment is cheaper." Stretching the term lowers the monthly payment but raises total interest, sometimes by tens of thousands. Compare the Total Interest card, not just the monthly figure.
- Forgetting this is principal and interest only. Real mortgage payments often bundle property tax, homeowners insurance, and mortgage insurance. This schedule shows the loan itself — your actual escrow payment will be higher.
- Expecting it to model extra payments. The schedule assumes the exact contractual payment each month. Paying extra principal would shorten the term, which this view does not simulate.
Where the calculation happens
The entire schedule is computed in your browser from the numbers you type — loan amount, rate, term, and start date. Nothing is sent to a server, no account is needed, and the CSV is generated locally on your device. The figures are a mathematical projection of a standard fixed-rate loan, not financial advice; your lender's actual amounts may differ slightly due to rounding conventions and fees.