Amortization Calculator
See your complete payment schedule and how each payment builds equity
$37,500 down · $337,500 loan · +$59/mo PMI at 740 credit →
Loan Summary
Monthly payment
$2,133/mo
P&I · + $59 PMI
Payoff date
Dec 2055
30 years
Total interest
$430,463
128% of the loan (TIP)
Total PMI paid
$5,611
until 80% LTV, 7.9 years in
Understanding Amortization
An amortization schedule is a table showing how each mortgage payment splits between interest and principal over the life of the loan, and what balance remains after each one. The payment stays the same; the split shifts steadily from interest toward principal. Amort means to kill — the loan balance, slowly. Interest on the entire balance is paid in full each month, plus a small portion towards principal, and as the balance decreases more of each payment goes to principal.
Balance Over Time
Amortization Schedule
| Year | Payment | Principal | Interest | Balance |
|---|---|---|---|---|
| 2026 | $25,599 | $3,772 | $21,826 | $333,728 |
| Jan 2026 | $2,133 | $305 | $1,828 | $337,195 |
| Feb 2026 | $2,133 | $307 | $1,826 | $336,888 |
| Mar 2026 | $2,133 | $308 | $1,825 | $336,580 |
| Apr 2026 | $2,133 | $310 | $1,823 | $336,270 |
| May 2026 | $2,133 | $312 | $1,821 | $335,958 |
| Jun 2026 | $2,133 | $313 | $1,820 | $335,644 |
| Jul 2026 | $2,133 | $315 | $1,818 | $335,329 |
| Aug 2026 | $2,133 | $317 | $1,816 | $335,012 |
| Sep 2026 | $2,133 | $319 | $1,815 | $334,694 |
| Oct 2026 | $2,133 | $320 | $1,813 | $334,374 |
| Nov 2026 | $2,133 | $322 | $1,811 | $334,051 |
| Dec 2026 | $2,133 | $324 | $1,809 | $333,728 |
| 2027 | $25,599 | $4,025 | $21,574 | $329,703 |
| 2028 | $25,599 | $4,295 | $21,304 | $325,408 |
| 2029 | $25,599 | $4,582 | $21,017 | $320,826 |
| 2030 | $25,599 | $4,889 | $20,710 | $315,937 |
| 2031 | $25,599 | $5,216 | $20,382 | $310,721 |
| 2032 | $25,599 | $5,566 | $20,033 | $305,155 |
| 2033 | $25,599 | $5,939 | $19,660 | $299,216 |
| 2034 | $25,599 | $6,336 | $19,263 | $292,880 |
| 2035 | $25,599 | $6,761 | $18,838 | $286,119 |
| 2036 | $25,599 | $7,213 | $18,385 | $278,906 |
| 2037 | $25,599 | $7,696 | $17,902 | $271,210 |
| 2038 | $25,599 | $8,212 | $17,387 | $262,998 |
| 2039 | $25,599 | $8,762 | $16,837 | $254,236 |
| 2040 | $25,599 | $9,349 | $16,250 | $244,887 |
| 2041 | $25,599 | $9,975 | $15,624 | $234,912 |
| 2042 | $25,599 | $10,643 | $14,956 | $224,270 |
| 2043 | $25,599 | $11,356 | $14,243 | $212,914 |
| 2044 | $25,599 | $12,116 | $13,483 | $200,798 |
| 2045 | $25,599 | $12,928 | $12,671 | $187,870 |
| 2046 | $25,599 | $13,793 | $11,805 | $174,077 |
| 2047 | $25,599 | $14,717 | $10,882 | $159,360 |
| 2048 | $25,599 | $15,703 | $9,896 | $143,657 |
| 2049 | $25,599 | $16,754 | $8,844 | $126,903 |
| 2050 | $25,599 | $17,876 | $7,722 | $109,027 |
| 2051 | $25,599 | $19,074 | $6,525 | $89,953 |
| 2052 | $25,599 | $20,351 | $5,248 | $69,602 |
| 2053 | $25,599 | $21,714 | $3,885 | $47,888 |
| 2054 | $25,599 | $23,168 | $2,431 | $24,720 |
| 2055 | $25,599 | $24,720 | $879 | $0 |
Extra principal only shortens the loan if your servicer applies it to principal. Today’s rates →
Altgage Inc. NMLS #2447252 | 100 Cambridge St, Floor 14, Boston, MA 02114|
How Amortization Works
Amortization is the schedule by which your fixed monthly payment slowly retires the loan. The payment stays the same every month, but the split between interest and principal shifts dramatically over time — and that shift is what makes early payoff strategies so powerful.
Why early payments are mostly interest
Each month's interest is calculated on the current balance. In year one, your balance is at its largest, so most of the payment goes to interest. As the balance comes down, the interest portion shrinks and principal grows — but on a 30-year loan, that crossover usually doesn't happen until somewhere around year 18.
20 years is the sweet spot
A 15-year loan saves the most interest, but the monthly payment jump can be steep. A 20-year term is often the sweet spot — a modest payment bump over a 30-year captures the majority of the benefit, typically $100K+ in lifetime interest savings and ten years off. Toggle 15 / 20 / 30 above and watch what happens to Total Interest and Payoff Date — the 20-year often gets you most of the way to 15-year savings for far less monthly pain.
How extra payments accelerate payoff
Any dollar applied directly to principal skips every future month of interest that dollar would have generated. Even small consistent extras can knock years off a 30-year loan. The earlier you add them, the more dramatic the effect — early dollars work harder than late ones. Curious about diminishing returns? Try the Prepay Curve calculator.
When to recast instead
If you have a large one-time sum — bonus, inheritance, proceeds from selling another property — recasting your mortgage re-amortizes the loan around the smaller balance, lowering your monthly payment without a refinance. Different tool, different goal. See if recasting beats just paying it down →
Download Your Amortization Schedule
Export the full schedule as CSV and it opens in any spreadsheet with the columns already laid out: payment number, date, scheduled payment, principal, interest, remaining balance, and running totals for principal and interest. Turn on extra payments and the extra gets its own column, kept separate from the scheduled amount — which is the column you need if you’re checking your own formulas. The file also carries the loan terms in a header block, so it still means something when you open it a month later.
That saves rebuilding it by hand, which is what most people searching for an amortization spreadsheet are about to do. The formulas aren’t hard — PMT for the payment, IPMT and PPMT for the split — but getting the extra-payment logic right is fiddly, and one wrong cell reference produces a schedule that looks plausible and isn’t.
If you do want to build your own, export this one first and check your version against it.
What negative amortization is
Negative amortization is when your payment doesn’t cover the interest accruing, so the shortfall is added to the balance and the loan grows instead of shrinking.
It doesn’t happen on a standard fixed-rate mortgage, where the payment is calculated to retire the loan over the term. It shows up in option-ARMs and payment-option products, in some graduated-payment structures, and in deferred-interest arrangements — and it’s the mechanism behind a reverse mortgage, where the balance growing over time is the design rather than a defect.
If you’re being offered a payment that seems too low for the balance and rate, this is the question to ask.
Frequently asked questions
What is amortization?
Amortization is the process of paying off a loan through fixed regular payments, each one covering the interest accrued since the last payment with the remainder reducing the principal. The payment amount stays constant while the split between interest and principal shifts steadily toward principal over the loan’s life.
What is an amortization schedule?
An amortization schedule is a table listing every payment over the loan’s life, showing for each one the amount going to interest, the amount going to principal, and the balance remaining afterward. It lets you see exactly where you’ll stand at any point in the loan.
Why is most of my mortgage payment going to interest?
Interest is charged on the outstanding balance, and early in the loan that balance is at its largest. On a typical 30-year mortgage the crossover — where more of the payment goes to principal than to interest — doesn’t arrive until somewhere around year eighteen.
How do I calculate an amortization schedule?
Each month, multiply the current balance by the monthly interest rate (annual rate divided by twelve) to get that month’s interest, subtract it from the payment to find the principal portion, then subtract the principal from the balance and repeat. The calculator above does this for every month of the term, including extra payments.
What is negative amortization?
Negative amortization is when a payment doesn’t cover the interest accruing, so the unpaid interest is added to the balance and the loan grows. It doesn’t occur on standard fixed-rate mortgages, but appears in option-ARM and payment-option products and is the underlying mechanism of a reverse mortgage.
Does an extra payment change my amortization schedule?
Yes. Extra principal reduces the balance immediately, so every subsequent month’s interest is calculated on a smaller number and the schedule ends earlier. Your required monthly payment doesn’t change — the loan just finishes sooner.
Can I get my amortization schedule in Excel?
Yes — export the schedule from the calculator above as CSV, which opens directly in Excel, Numbers or Google Sheets. It carries payment date, scheduled payment, principal, interest, remaining balance and running totals, with any extra payment in its own column, plus a header block recording the loan terms. That’s usually faster and less error-prone than building the PMT, IPMT and PPMT formulas by hand.