Amortization Calculator
It produces a full month-by-month schedule for any loan, showing how each payment splits between interest and principal, and what an extra monthly payment saves.
Monthly payment
$1,896.20
Total interest
$382,633
Total repaid
$682,633
Payments
360
Interest saved
$0
Months saved
0
Interest / principal
128%
| Yr | Principal | Interest | Balance |
|---|---|---|---|
| 1 | $3,353 | $19,401 | $296,647 |
| 2 | $3,578 | $19,177 | $293,069 |
| 3 | $3,817 | $18,937 | $289,252 |
| 4 | $4,073 | $18,681 | $285,179 |
| 5 | $4,346 | $18,409 | $280,833 |
| 6 | $4,637 | $18,118 | $276,196 |
| 7 | $4,947 | $17,807 | $271,249 |
| 8 | $5,279 | $17,476 | $265,970 |
| 9 | $5,632 | $17,122 | $260,338 |
| 10 | $6,009 | $16,745 | $254,328 |
| 11 | $6,412 | $16,343 | $247,916 |
| 12 | $6,841 | $15,913 | $241,075 |
| 13 | $7,299 | $15,455 | $233,776 |
| 14 | $7,788 | $14,966 | $225,987 |
| 15 | $8,310 | $14,445 | $217,677 |
| 16 | $8,866 | $13,888 | $208,811 |
| 17 | $9,460 | $13,294 | $199,351 |
| 18 | $10,094 | $12,661 | $189,257 |
| 19 | $10,770 | $11,985 | $178,487 |
| 20 | $11,491 | $11,263 | $166,996 |
| 21 | $12,261 | $10,494 | $154,735 |
| 22 | $13,082 | $9,673 | $141,653 |
| 23 | $13,958 | $8,797 | $127,695 |
| 24 | $14,893 | $7,862 | $112,803 |
| 25 | $15,890 | $6,864 | $96,912 |
| 26 | $16,954 | $5,800 | $79,958 |
| 27 | $18,090 | $4,665 | $61,868 |
| 28 | $19,301 | $3,453 | $42,567 |
| 29 | $20,594 | $2,161 | $21,973 |
| 30 | $21,973 | $781 | $0 |
What it calculates
It produces a full month-by-month schedule for any loan, showing how each payment splits between interest and principal, and what an extra monthly payment saves.
Why it matters
Early payments are almost entirely interest, which is invisible until you see the table. Overpaying early removes far more interest than the same amount overpaid later.
Who it's for
Mortgage holders planning overpayments, borrowers checking a lender's figures, and anyone wanting to see where their money actually goes.
Formula
- P
- Loan principal
- r
- Monthly interest rate
- n
- Number of scheduled payments
- Extra
- Additional principal paid each month
Worked example
$300,000 at 6.5% over 30 years, with $300 a month extra
- 1Scheduled payment = $1,896.20
- 2Each month: interest = balance × r, remainder cuts the principal
- 3The extra $300 goes entirely against principal
Clears the loan years early and saves six figures in interest
How the amortization calculator works
Each payment covers the interest accrued that month first; whatever is left reduces the balance. Because the balance falls, the interest portion shrinks and the principal portion grows, even though the payment never changes. An extra payment goes entirely against principal, so it removes every future month of interest that principal would have generated — which is why the saving is so much larger than the payment itself, and why an overpayment in year one is worth many times the same amount in year twenty.
Each payment covers the interest accrued that month first; whatever is left reduces the balance. Because the balance falls, the interest portion shrinks and the principal portion grows even though the payment never changes.
An extra payment goes entirely against principal, so it removes every future month of interest that principal would have generated. That is why the saving dwarfs the payment, and why overpaying early is worth many times the same amount later.
Common mistakes
- Assuming half the term means half the balance repaid — on a 30-year loan you are nowhere near halfway at year 15.
- Overpaying without checking whether the lender applies it to principal or simply holds it.
- Missing early repayment charges on a fixed deal.
Tips and best practice
- Overpay as early as you can; the interest saved compounds across every remaining month.
- Ask your lender to keep the term and reduce the balance rather than lowering the payment.
- Even one extra payment a year removes several years from a typical 30-year mortgage.
Frequently asked questions
What is an amortization schedule?
A month-by-month table showing each payment split into interest and principal, with the balance after every payment. It reveals how heavily front-loaded the interest is.
Why is so much of my early payment interest?
Interest is charged on the outstanding balance, which is at its largest at the start. As the balance falls the interest shrinks and more of each identical payment goes to principal.
How much does one extra payment a year save?
On a typical 30-year mortgage it removes roughly four to six years and a large share of total interest, because the extra goes entirely against principal.
Is it better to overpay or invest the difference?
Overpaying is a guaranteed return equal to your mortgage rate, tax-free. Investing may return more but is not guaranteed. The higher your rate, the stronger the case for overpaying.
Will overpaying reduce my monthly payment?
Usually it shortens the term instead, which saves far more interest. Some lenders will recalculate the payment on request, but that gives up most of the benefit.
Related calculators
Methodology & trust
- Formula source
- Standard amortizing loan schedule with additional principal payments.
- Last updated
- 2026-07-28
- Privacy
- Every calculation runs in your browser. No inputs are sent to a server or stored.
- Accessibility
- Keyboard navigable, labeled inputs and WCAG AA color contrast.