30-Year Fixed Mortgage Amortization Table Calculator

A 30-year fixed mortgage amortization table shows how each monthly principal-and-interest payment is divided between interest and principal, and how the balance declines over time. Enter the loan amount and annual interest rate to calculate the level monthly payment and total interest; the schedule itself can be generated month by month from those inputs.

Formula

The fixed monthly payment is calculated by spreading repayment of the principal and interest over the full number of monthly payments:

Payment = P × r ÷ [1 − (1 + r)⁻ⁿ]

• P is the amount borrowed, in dollars.
• r is the monthly interest rate, calculated as annual APR ÷ 1,200. For a 6.5% APR, r = 0.065 ÷ 12.
• n is the total number of monthly payments: loan term in years × 12.

The calculator rounds the monthly payment to cents. Total interest is calculated as the rounded payment multiplied by the number of payments, minus the original loan amount. This is a summary, not the full amortization table: each row in a table needs the opening balance, interest charged, principal repaid, and closing balance for that month.

Worked Example

Using the default inputs of $300,000, a 6.5% annual APR, and 30 years:

1. Convert the annual rate to a monthly rate: 6.5 ÷ 1,200 = 0.0054166667.
2. Find the payment count: 30 × 12 = 360 months.
3. Substitute into the payment formula: $300,000 × 0.0054166667 ÷ [1 − (1.0054166667)⁻³⁶⁰].
4. Round the result to cents: the monthly principal-and-interest payment is $1,896.20.
5. Calculate total interest using the rounded payment: $1,896.20 × 360 − $300,000 = $382,632.00.

These figures describe scheduled payments under the stated assumptions. They do not include property-related charges or changes caused by extra payments, missed payments, or a loan modification.

Assumptions

• The interest rate is fixed for the entire term.
• Payments are made monthly, with the first payment one month after the loan begins.
• Interest is modelled monthly using APR ÷ 12.
• The calculation excludes fees, taxes, insurance, mortgage insurance, escrow, and other charges.
• Payments are level and made on schedule; no extra principal or payment changes are included.

How to Read a 30-Year Amortization Table

A full table normally has one row for each of 360 monthly payments. The first row starts with the original balance. Monthly interest is calculated on the balance before that payment; the portion left after interest is applied to principal. Subtract that principal portion from the opening balance to get the closing balance. That closing balance becomes the next row’s opening balance.

For the example, the first month’s interest is approximately $300,000 × 0.0054166667, or $1,625. The scheduled payment is $1,896.20, so about $271.20 goes to principal and the balance becomes about $299,728.80. Small differences can appear if the table rounds each row to cents; the calculator’s summary uses the stated level payment and does not display each row’s rounding.

• Opening balance: amount owed before the monthly payment.
• Payment: scheduled principal and interest.
• Interest: the period’s interest cost based on the opening balance.
• Principal: the payment amount remaining after interest.
• Closing balance: opening balance minus principal repaid.

Early in a long-term loan, the balance is large, so more of a level payment typically goes to interest. As the balance falls, interest for each month falls and more of the same payment goes to principal. A fixed rate means the rate does not change in this model; it does not mean the interest and principal portions stay equal.

What the Table Includes—and What It Does Not

“Fixed” refers to the loan’s interest rate under the model, and the payment shown is principal and interest only. A mortgage bill can also include amounts for property taxes, homeowners insurance, mortgage insurance, or escrow, depending on the loan and payment arrangement. Those amounts are not part of this calculation and may change over time even when the mortgage rate is fixed.

The term “30-year” means 360 scheduled monthly payments in this standard monthly model. It does not mean that every borrower’s actual payoff must occur on that date: additional principal payments, delayed or missed payments, refinancing, or other changes can alter the schedule. The precise treatment of payments and interest can also depend on the loan documents and servicing calculations.

Common Questions About the Schedule

A frequent misconception is that the borrower pays only interest at the beginning and starts paying principal later. In a standard fully amortizing fixed-payment loan, each scheduled payment includes principal from the start, although the initial principal portion may be smaller than the interest portion. Another point to keep in mind is that a payment estimate is not the same as a complete monthly household-cost estimate.

To compare a lender’s schedule with a calculation, use the same starting principal, rate, term, payment timing, and rounding approach. Check whether quoted payments include only principal and interest or also other charges. A lender’s official disclosure and payment schedule may use loan-specific details that this general arithmetic does not model.

Frequently Asked Questions

How many payments are in a 30-year fixed mortgage?
A standard monthly schedule has 360 payments: 30 years multiplied by 12 months. The actual contract and payment history determine the applicable schedule for a particular loan.

Does a fixed mortgage payment stay the same for all 30 years?
The principal-and-interest payment is level in this calculation when the rate and terms stay fixed. The total amount due may differ if taxes, insurance, escrow, or other charges are included and change.

Why does the table show more interest at the beginning?
Monthly interest is calculated on the balance at the start of the period. That balance is largest near the beginning, so the interest share of a level payment is initially larger; it generally declines as principal is repaid.

Does the calculator include property taxes or homeowners insurance?
No. It estimates principal and interest only. Taxes, insurance, mortgage insurance, escrow, and fees require separate figures and are not included in this calculator.

Can extra payments change an amortization table?
Yes. An additional amount applied to principal can reduce the balance and change future interest and payoff timing. This calculator assumes only the scheduled level payment, so it does not model extra payments.

This result is an estimate; the lender’s disclosure gives the exact figures.

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in p | Loan amount | $ | 300000 | 1 | 100000000
in apr | Interest rate (APR) | % | 6.5 | 0.01 | 100
in yrs | Loan term | years | 30 | 0.0833 | 50
out pmt | Monthly principal-and-interest payment | $ | round(p * (apr / 1200) / (1 - (1 + apr / 1200) ^ -(yrs * 12)), 2) | 2
out int | Total interest over the loan term | $ | pmt * yrs * 12 - p | 2