Amortization schedule calculator
Build a full month-by-month amortization schedule with extra payments and lump sums, then export it to CSV, Excel or PDF.
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- Nothing you enter is sent
- Free, no account
Total interest
$389,303.05
Total repaid
$709,303.05
principal + interest
Payoff date
January 1, 2056
30 years
Interest as % of loan
121.7%
of the amount borrowed
Add an overpayment on the left to see how much interest disappears and how many payments come off the end of the loan.
- Principal45.1%$320,000.00
- Interest54.9%$389,303.05
Split of everything you will hand over across the whole loan.
- Scheduled balance
Formula and working
Monthly payment
M = P × i / (1 − (1 + i)^−n) i = 6.25% ÷ 12 = 0.00520833 n = 30 × 12 = 360 M = 320,000 × 0.00520833 ÷ (1 − 1.00520833^−360) = $1,970.30
First payment split
Interest₁ = balance × i, Principal₁ = M − Interest₁ Interest₁ = 320,000 × 0.00520833 = $1,666.67 Principal₁ = $1,970.30 − $1,666.67 = $303.63
Total interest
Interest = Σ (opening balance × i) over every payment total repaid $709,303.05 − principal $320,000.00 = $389,303.05
Every figure on this page is computed with 40-digit decimal arithmetic and rounded once, at the end, the way a loan servicer rounds.
| # | Date | Payment | Principal | Interest | Balance |
|---|---|---|---|---|---|
| 1 | Feb 2026 | $1,970.30 | $303.63 | $1,666.67 | $319,696.37 |
| 2 | Mar 2026 | $1,970.30 | $305.21 | $1,665.09 | $319,391.16 |
| 3 | Apr 2026 | $1,970.30 | $306.80 | $1,663.50 | $319,084.36 |
| 4 | May 2026 | $1,970.30 | $308.40 | $1,661.90 | $318,775.96 |
| 5 | Jun 2026 | $1,970.30 | $310.01 | $1,660.29 | $318,465.95 |
| 6 | Jul 2026 | $1,970.30 | $311.62 | $1,658.68 | $318,154.33 |
| 7 | Aug 2026 | $1,970.30 | $313.25 | $1,657.05 | $317,841.08 |
| 8 | Sep 2026 | $1,970.30 | $314.88 | $1,655.42 | $317,526.20 |
| 9 | Oct 2026 | $1,970.30 | $316.52 | $1,653.78 | $317,209.68 |
| 10 | Nov 2026 | $1,970.30 | $318.17 | $1,652.13 | $316,891.51 |
| 11 | Dec 2026 | $1,970.30 | $319.82 | $1,650.48 | $316,571.69 |
| 12 | Jan 2027 | $1,970.30 | $321.49 | $1,648.81 | $316,250.20 |
Showing 1–12 of 360 rows
Assumptions
- A fixed nominal rate compounded monthly, with equal payments made on the same day each month.
- Interest accrues on the opening balance rather than daily, which is how most fixed-rate mortgages and instalment loans are serviced. Loans that accrue daily will differ by a few units of currency over the term.
- Overpayments are applied to principal in the month they are made, with no prepayment penalty. Check your loan agreement — some lenders hold extra money as a prepaid instalment instead.
- Property tax, insurance, PMI and arrangement fees are outside the amortization and are not included in the totals.
- The last instalment is adjusted so the balance lands exactly on zero, matching normal servicer practice.
What an amortization schedule actually tells you
A loan quote gives you one number: the monthly payment. An amortization schedule gives you the other three hundred and sixty. It shows, payment by payment, how much of your money is buying down the debt and how much is simply renting it — and on a long loan those two figures start out wildly lopsided.
On a 320,000 loan at 6.25% over thirty years, the payment is 1,970.30. Of the first one, 1,666.67 is interest and only 303.63 touches the balance. It takes until payment 228 — most of the way through year nineteen — before principal finally exceeds interest. That crossover point is marked under the balance chart above, with your own numbers.
The formula, and why it looks like that
The level payment on a fixed-rate loan comes from the annuity formula:
M = L × i / (1 − (1 + i)^−n) L is the amount borrowed, i is the monthly interest rate (the annual
nominal rate divided by twelve) and n is the number of payments. The denominator is
the present-value factor of an annuity — it answers "what single sum today is worth n payments
of one unit, discounted at i?" — so dividing the loan by it gives the payment that exactly
exhausts the debt in n months.
Each month the schedule then does two lines of arithmetic: interest is the opening balance times
i, and everything left over from the payment reduces the principal. That is the
whole mechanism. Everything else — the shape of the curve, the crossover point, the reason
overpayments are so effective — falls out of those two lines.
Why overpaying works so well
An extra payment is not a discount on the debt; it is the cancellation of every future interest charge that money would have generated. Paying 1,000 off a 6.25% loan with twenty years to run does not save 62.50 of interest — it saves the compounding on 1,000 for twenty years, which is roughly 2,450.
That is why the saving is so front-loaded. The same 1,000 paid in year 28 saves almost nothing, because there was almost no interest left to cancel. If you are going to overpay, early is worth dramatically more than large.
| Extra per month | Term becomes | Interest saved |
|---|---|---|
| 0 | 30 yr 0 mo | — |
| 100 | 26 yr 3 mo | 57,725 |
| 250 | 22 yr 4 mo | 115,679 |
| 500 | 18 yr 1 mo | 175,303 |
| 1,000 | 13 yr 3 mo | 238,435 |
For a 320,000 loan at 6.25% over 30 years, whose scheduled interest is 389,303. Run your own figures above — the calculator reports the exact saving and the new payoff date.
Before you overpay, check two things
- Prepayment penalties. Rare on US conventional mortgages, common on some European fixed-rate deals, and normal on subprime car finance. Read the agreement.
- How the payment is applied. Many servicers treat unmarked extra money as a prepaid instalment rather than a principal reduction, which saves you nothing. You usually have to say "apply to principal" explicitly, in writing, every time.
Reading the schedule
- Payment — the total leaving your account, including any extra principal.
- Interest — the opening balance multiplied by the monthly rate.
- Principal — the scheduled part of the payment that reduces the debt.
- Extra — any overpayment, applied to principal in the same month.
- Interest to date — the running total, which is the figure worth watching.
- Balance — what you owe after that payment clears.
The yearly tab collapses the same data into calendar years, which is the view lenders and tax preparers usually want. The Excel export contains both views as separate sheets; the CSV export is the monthly schedule, and the PDF prints both.
Precision
Every figure is computed with 40-digit decimal arithmetic rather than floating point, and rounded to the minor currency unit once, at the point a servicer would round it. Interest is charged on the opening balance and rounded to the cent each month, which is standard practice for fixed-rate mortgages and instalment loans. A schedule from this page matches a lender statement to the penny for a standard fixed-rate loan.
Loans that accrue interest daily — some HELOCs and Canadian variable mortgages — will differ by a few units over a full term, because the daily method charges slightly more when payment dates fall late in a long month.
Nothing here leaves your device
Your loan balance, rate and payoff plan are financial fingerprints. This page runs the entire calculation in your browser: there is no server, no account, no lead capture and no request to any third party. Open the network tab while you type and watch it stay empty, or turn off Wi-Fi and keep working — the schedule and all three export formats are generated locally.
Questions
What is an amortization schedule?
It is the payment-by-payment plan for a loan: how much of each instalment goes to interest, how much reduces the balance, and what is still owed afterwards. Early payments are mostly interest because interest is charged on whatever you still owe.
How much interest do extra payments actually save?
Every extra unit of principal cancels all the future interest that unit would have carried. On a 30-year loan at 6.25%, an extra 200 a month typically removes several years and tens of thousands in interest — enter your own numbers above and the saving is shown next to the schedule.
Why does the last payment differ from the others?
The level payment is rounded to the cent, which leaves a small remainder after the final scheduled instalment. Lenders absorb it in the last payment rather than adding an extra month, and this calculator does the same.
Can I export the schedule?
Yes — CSV, Excel (.xlsx) and PDF, all generated in your browser. Nothing is uploaded, so a schedule containing your real loan balance never touches a server.
Does this work for car loans and personal loans?
Yes. Any fixed-rate instalment loan with equal monthly payments amortises the same way — mortgages, car finance, student loans and personal loans all use this formula.