What this calculator does
See exactly where every loan payment goes, from the first one to the last. For a fixed-rate loan, this calculator builds the full payment plan, called an amortization schedule. It shows your monthly payment and how much of each one goes to interest versus paying down the loan. It also shows what you still owe after every payment, the interest you've paid so far and the month of your final payment.
Every payment on this kind of loan is the same size, but what it pays for changes over time. Early on, most of it covers interest. Toward the end, most of it pays down what you owe. You can view the schedule year by year. Or switch to every payment to see the exact split, the month and what you owe after each one.
Where it's used
Why this math matters outside the classroom:
- Splitting a payment. On a $200,000 loan at 6% for 30 years, the first $1,199.10 payment is $1,000 of interest and $199.10 of principal.
- Tracking the balance. Borrowers read an amortization table to see what they would still owe after 5 or 10 years of regular payments.
- Year-end statements. Homeowners add up the interest column for a calendar year to match the interest shown on a lender's annual statement.
- Algebra 2 projects. Students build a month-by-month table in a spreadsheet and check that the last row brings the balance to zero.
- Comparing loan terms. Lenders show how a 15-year schedule pays principal down far faster in the early years than a 30-year schedule.
Grade level and standards: Grades 11–12; Common Core State Standards for Mathematics HSA.SSE.B.4. © Copyright 2010. National Governors Association Center for Best Practices and Council of Chief State School Officers. All rights reserved.
How to use it
- Enter how much you borrowed and the yearly interest rate.
- Enter the length of the loan in years or months, and set the date it starts.
- Choose a yearly summary or every payment. Then read your payment, total interest, payoff date and the schedule table.
What the inputs mean
- Loan amount
- How much you owe when the schedule starts, also called the principal. For a mortgage, that's the price minus your down payment.
- Annual interest rate
- Your loan's yearly interest rate. Each month's interest is what you still owe times this rate ÷ 12.
- Loan term
- Up to 50 years or 600 months. If you enter years, the calculator turns them into whole months.
- Loan start date
- The date your loan begins. The first payment is a month later. So row 1 of a loan starting in October 2026 is November 2026.
- Schedule view
- Every payment shows one row per month. For a long mortgage, that can be several hundred rows.
Formula and method
i = rate ÷ 100 ÷ 12; n = number of monthly payments payment = P × i ÷ (1 − (1 + i)^(−n)); at 0%: payment = P ÷ n interest for a month = balance × i principal for a month = payment − interest new balance = balance − principal principal first exceeds interest at the first payment k with (1 + i)^(n − k + 1) < 2
In the formulas, P is the amount you borrow, i is the monthly interest rate and n is the number of monthly payments. The balance is what you still owe, and k is a payment's number in the schedule.
The payment formula finds the one monthly amount that pays off the loan, with interest, in exactly n months. The schedule then works through it one month at a time. Each month, interest is charged on what you still owe. The rest of the payment pays down the loan.
Because you owe a little less each month, each month's interest is a little smaller than the last. So more of each payment goes to the loan itself. The last payment is set to clear what's left exactly. The last formula finds the crossover: the first payment where more goes to the loan than to interest.
Worked example
A $250,000 loan at 6% for 30 years.
- Monthly rate: 6% ÷ 12 = 0.005; payments: 30 × 12 = 360.
- Payment: $250,000 × 0.005 ÷ (1 − 1.005^(−360)) ≈ $1,498.88.
- First month: interest = $250,000 × 0.005 = $1,250.00, so principal = $1,498.88 − $1,250.00 = $248.88.
- After year 1 you have paid $14,916.49 of interest and $3,070.03 of principal, leaving $246,929.97.
Result: Total interest over 30 years is about $289,595.47. Payment 223 is the first where more goes to the loan than to interest. You don't owe less than half the original amount until payment 252. A loan starting on October 18, 2026 makes its last payment in October 2056.
Understanding the result
If your balance falls slowly at first, don't worry: that's normal for long loans. It's why extra payments made early save the most interest. It's also why, if you sell or refinance in the first few years, you'll still owe most of what you borrowed.
The interest-to-date column shows what borrowing has cost you so far. That's handy when you're weighing a refinance or paying extra.
Assumptions and limitations
- The rate stays the same for the whole loan, and interest is charged each month at the yearly rate ÷ 12.
- You pay once a month, at the end of each month, starting one month after the loan begins.
- Payments aren't rounded to the cent. The last payment clears whatever is left.
- Escrow costs, such as property tax and insurance your lender collects, aren't part of this schedule.
- It doesn't handle changing rates, skipped payments, interest-only periods or balloon payments (a big lump sum due at the end).
- Lenders that charge interest daily or round each payment will show small differences.
- Rows show the month only. Your actual due day depends on your loan agreement.
Frequently asked questions
Why does so little of my early payment go to the loan itself?
Interest is charged on what you still owe, and that's largest at the start. On a $250,000 loan at 6% for 30 years, the first payment is $1,498.88. Of that, $1,250.00 is interest.
When will I have repaid half the loan?
On most loans, later than halfway through. The result called 'Payment when half the loan is repaid' shows the exact payment number for your numbers.
Is this the same as my mortgage statement?
For a fixed-rate loan, it should be very close. Your statement may differ by a few cents because of rounding. It often includes escrow amounts too, which this schedule leaves out.
When does more of my payment go to the loan than to interest?
At the crossover point, shown as 'First payment that is mostly principal'. On a 30-year loan at 6%, it's payment 223, a little past year 18. Higher rates push it later and shorter loans bring it sooner. On a 15-year loan at 6%, it's payment 43.
What does it mean for a loan to be fully amortizing?
It means your regular payments alone bring what you owe to exactly zero by the end, with no lump sum left over. Interest-only and balloon loans aren't fully amortizing. With those, some or all of the loan is still owed when the regular payments stop.
How do extra payments change the schedule?
Paying extra toward the loan lowers what you owe sooner. That cuts the interest in every later month and ends the loan early. Use the extra payment calculator to compare the two schedules.
How this calculator is checked
Method: Standard level-payment (annuity) formula with monthly rate = yearly rate ÷ 12, applied month by month. The calculation is covered by automated tests with known reference values and edge cases. Last updated 2026-10-18. Found a problem? Tell us.
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