30 Year Amortization Table: Payment and Balance

This 30-year amortization calculator estimates a fixed monthly loan payment and the balance remaining after each scheduled payment; its formula can generate the full month-by-month table. Enter the loan amount, annual APR, and loan term in years to see the payment and total interest, then use the schedule guidance below to interpret the results.

Formula

The standard fixed-payment amortization formula calculates a level monthly payment that pays principal and interest over the stated term:

M = round(P × r ÷ [1 − (1 + r)⁻ⁿ], 2)

• P is the starting loan principal in dollars.
• APR is the annual percentage rate entered as a percentage, such as 6 for 6%.
• r is the monthly rate, calculated as APR ÷ 1,200.
• n is the number of monthly payments, calculated as years × 12.
• M is the scheduled monthly payment in dollars, rounded to cents.

The calculator then estimates total interest as I = M × n − P. Because it uses the rounded monthly payment, this total reflects payment rounding rather than an unrounded mathematical payment.

Worked Example

Using the defaults, the principal is $200,000, APR is 6%, and term is 30 years.

1. Monthly rate: 6 ÷ 1,200 = 0.005.
2. Number of payments: 30 × 12 = 360.
3. Payment before rounding: $200,000 × 0.005 ÷ [1 − (1.005)⁻³⁶⁰] ≈ $1,199.101.
4. Monthly payment rounded to cents: $1,199.10.
5. Total of scheduled payments: $1,199.10 × 360 = $431,676.00.
6. Estimated total interest: $431,676.00 − $200,000 = $231,676.00.

Assumptions

• The interest rate stays fixed for the entire term.
• Payments are made monthly at the end of each period, with the first payment one month after the loan begins.
• Interest is modelled monthly at APR ÷ 12; the APR is treated as a nominal annual rate.
• Fees, taxes, insurance, PMI, escrow, and extra payments are not included.

Reading a 30-Year Amortization Table

An amortization table is a schedule with one row for each payment period. A useful row typically shows the payment number or date, beginning balance, payment, interest portion, principal portion, and ending balance. This calculator gives the fixed payment and term-wide interest total; the same standard formula can produce each row when the monthly rate and payment are known.

For a month’s row, multiply the starting balance by the monthly rate to estimate that month’s interest. Subtract that interest from the scheduled payment to find the principal reduction, then subtract the principal reduction from the starting balance. For example, on the first default-value payment, interest is $200,000 × 0.005 = $1,000. The $1,199.10 payment therefore reduces principal by $199.10, leaving an estimated balance of $199,800.90.

Early in a long repayment schedule, the balance is large, so the interest share of each payment can be substantial. As principal declines, the interest charged each month generally declines too, and more of a level payment goes toward principal. The monthly payment remains the same under the fixed-rate assumptions, but its allocation changes over time.

When to Use the Estimate

Use the calculation to understand how principal, APR, and term determine a scheduled payment, or to create a baseline for reviewing a lender-provided payment schedule. For a complete 30-year table, repeat the monthly balance calculation for payment numbers 1 through 360, carrying each ending balance forward as the next month’s starting balance. A spreadsheet can automate those rows, but keep full precision in balances during the calculation and round displayed dollar amounts to cents.

The stated term matters: 30 years means 360 monthly periods. A different term changes both the scheduled payment and the total number of payments. The APR is an input, not a current-market estimate; use the rate and loan amount supplied in the relevant disclosure when comparing its figures with this arithmetic.

Common Mistakes and Limits

Do not enter 6 when you mean 0.06%; the APR field expects a percentage, so 6 means 6%. The formula converts it to a monthly decimal rate by dividing by 1,200. Also avoid entering months in the years field: enter 30 for a 30-year term, not 360.

Rounding can create small differences from another schedule. This calculator rounds the payment to cents and uses that rounded payment for total interest, while a lender’s system may handle the final payment or daily interest differently. A real loan may have fees, payment dates, variable-rate terms, or other charges not captured here. Extra principal payments also change the balance path and can shorten repayment, so they cannot be represented by this fixed-payment result alone.

This is estimate arithmetic for education, not financial advice. Obtain the actual APR, payment, fees, and schedule from the lender’s disclosure; the result is an estimate and the lender’s disclosure gives the exact figures.

How to Use This List

Start with the calculator inputs that match the loan principal, annual APR, and term you want to examine. Treat the output as a baseline, then check a lender’s disclosed schedule for its actual payment dates, fees, and final-payment treatment. To build the table, use the first-month example above and repeat the interest, principal, and ending-balance steps for each subsequent month.

Frequently Asked Questions

What does a 30-year amortization table show?
It shows how each scheduled payment is divided between interest and principal and how the balance changes over 360 monthly periods.

Does the monthly payment include property taxes or insurance?
No. This calculation includes principal and interest only; taxes, insurance, PMI, and escrow are excluded.

Why does the principal portion grow over time?
As the outstanding balance falls, monthly interest calculated on that balance usually falls, leaving more of a level payment to reduce principal.

Can I use this for a variable-rate loan?
Only as a fixed-rate estimate for the APR entered; it does not model future rate changes or payment adjustments.

Why might a lender’s payment differ by a few cents?
Rounding conventions, payment timing, fees, and the handling of the final payment can differ from this simplified calculation.

Final Thoughts

A 30-year amortization table makes the changing mix of interest and principal visible across a long repayment term. Use the formula to understand the schedule’s mechanics, and rely on the lender’s disclosure for the exact loan figures.

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in p | Loan amount | $ | 200000 | 1 | 100000000
in apr | Interest rate (APR) | % | 6 | 0.01 | 100
in yrs | Loan term | years | 30 | 0.0833 | 50
out pmt | Monthly payment | $ | round(p * (apr / 1200) / (1 - (1 + apr / 1200) ^ -(yrs * 12)), 2) | 2
out int | Total interest | $ | pmt * yrs * 12 - p | 2