# What is my amortization schedule?

Computes the monthly payment and the payment-by-payment amortization schedule of a fixed-rate loan, with optional extra monthly, yearly, and one-time payments.

- Page: https://www.acalculator.org/finance/amortization-calculator
- JSON spec: https://www.acalculator.org/finance/amortization-calculator.json
- Version: 162719887247

## Default answer

Example with the default inputs (Loan amount $250,000.00, Interest rate (APR) 6.5%, Loan term (years) 30, Plus months 0, Loan start date September 29, 2026, Extra each month $0.00, Extra each year $0.00, One-time extra payment $0.00, With payment number 12) on the example date Tuesday, September 29, 2026: A $250,000.00 loan at 6.5% is repaid with $1,580.17 a month; with the payments shown it takes 360 payments and $318,861.22 of interest.

## Inputs

| Key | Label | Description |
| --- | --- | --- |
| amount | Loan amount | The amount borrowed. |
| rate | Interest rate (APR) | The yearly interest rate. The monthly rate is this divided by 12. |
| years | Loan term (years) | The length of the loan in whole years. |
| months | Plus months | Months added to the years, from 0 to 11. |
| start | Loan start date | The day the loan starts. The first payment is one month later. |
| extra | Extra each month | An extra amount paid with every monthly payment. It goes straight to the balance. |
| yearly | Extra each year | An extra amount paid once a year, with every 12th payment. |
| once | One-time extra payment | A single extra amount paid with the payment number below. |
| onceat | With payment number | The payment the one-time extra amount is paid with, counting from 1. |

## Outputs

| Key | Label | Description |
| --- | --- | --- |
| payment | Monthly payment | The level monthly payment that repays the loan over its term, without extra payments. |
| amount | Loan amount | The amount borrowed. |
| interest | Total interest | All the interest paid, with any extra payments. |
| paid | Total of payments | The loan amount plus all the interest. |
| payments | Number of payments | How many monthly payments it takes to repay the loan, with any extra payments. |
| payoff | Paid off in | The month of the last payment, when a start date is given. |
| saved | Interest saved by paying extra | The interest the extra payments save, compared with the schedule without them. |
| sooner | Months saved by paying extra | How many fewer monthly payments the extra payments take. |

## Method

payment = L × r ÷ (1 − (1 + r)^−n), with L the loan amount, r the APR ÷ 12, and n the number of months; each month, interest = balance × r, and the payment plus any extra, minus the interest, lowers the balance.

## Assumptions

- The rate is fixed and interest is charged monthly at APR ÷ 12 on the balance.
- Payments are made at the end of each month, starting one month after the start date.
- Extra payments go straight to the balance; the yearly extra is paid with payments 12, 24, 36, and so on.
- The last payment is whatever is left, so the principal parts add up to the loan amount.
- Values are not rounded to the cent between months; only the display is rounded.

## Worked examples

1. amount = $200,000.00, rate = 6%, years = 30 gives payment = $1,199.10, interest = $231,676.38, payments = 360. Source: hand calculation in content.mdx; Python 3 cross-check in docs/progress/WP-31/python/amortization.py.
2. amount = $10,000.00, rate = 0%, years = 1, months = 6, start = 2026-10-15 gives payment = $555.56, interest = $0.00, payments = 18, payoff = 2028-04-15. Source: hand calculation in content.mdx: 10,000 ÷ 18.
3. amount = $200,000.00, rate = 6%, years = 30, extra = $200.00 gives payments = 252, interest = $151,875.87, saved = $79,800.51, sooner = 108. Source: hand calculation in content.mdx, month by month in Python (docs/progress/WP-31/python/amortization.py).
4. amount = $100,000.00, rate = 5%, years = 15, yearly = $1,000.00, once = $10,000.00, onceat = 24 gives payment = $790.79, payments = 138, interest = $29,822.43. Source: month by month in Python (docs/progress/WP-31/python/amortization.py), rule in content.mdx.

## FAQ

### What is an amortization schedule?

It is a table of every payment on a loan. Each row shows how much of the payment pays interest, how much lowers the balance (principal), and the balance left after the payment. The schedule above shows it by year or by month.

### Why is most of my early payment interest?

Interest each month is the balance times the monthly rate. At the start the balance is at its highest, so the interest is too, and only a small part of the level payment is left to lower the balance. As the balance falls, the interest falls and more of the same payment goes to principal. On a $200,000 loan at 6% over 30 years, the first payment of $1,199.10 is $1,000 of interest and $199.10 of principal.

### How do extra payments change the schedule?

An extra payment goes straight to the balance. A lower balance means less interest next month, so more of every later payment goes to principal and the loan ends sooner. Paying $200 more each month on a $200,000 loan at 6% over 30 years ends it after 252 payments instead of 360 and saves $79,800.51 of interest.

### Does an extra payment lower my monthly payment?

No. On a normal fixed-rate loan the payment stays the same and the loan ends sooner. Some lenders will recalculate a lower payment after a large extra payment (a recast); see the mortgage recast calculator for that case.

### Is the monthly rate the APR divided by 12?

For most US mortgages and auto loans, yes: interest is charged monthly at the yearly rate divided by 12. This page uses that rule. A loan that compounds on a different schedule has a slightly different payment; the loan calculator lets you pick the compounding.

### Can a lender charge me for paying early?

Some loans have a prepayment penalty, a fee for paying off all or part of the loan early. The CFPB notes that it does not normally apply to small extra principal payments, but check your loan papers before you pay a large amount.

## Sources

- Consumer Financial Protection Bureau, What is amortization and how could it affect my auto loan? https://www.consumerfinance.gov/ask-cfpb/what-is-amortization-and-how-could-it-affect-my-auto-loan-en-771/
- Consumer Financial Protection Bureau, How does paying down a mortgage work? https://www.consumerfinance.gov/ask-cfpb/how-does-paying-down-a-mortgage-work-en-1943/
- Consumer Financial Protection Bureau, What is a prepayment penalty? https://www.consumerfinance.gov/ask-cfpb/what-is-a-prepayment-penalty-en-1957/
- Amortized loan payment (annuity) formula: S. A. Broverman, Mathematics of Investment and Credit, chapter 3 (loan payment and amortization schedule).