30-Year Loan Amortization Schedule Calculator

This calculator estimates the monthly payment and total interest for a fixed-rate loan repaid over 30 years, and shows the payment-by-payment amortization schedule. Enter the loan amount and annual APR to see how each monthly payment is split between interest and principal.

Formula

The fixed monthly payment uses the standard level-payment amortization formula: M = P × r ÷ [1 − (1 + r)⁻ⁿ], rounded to cents. Here, M is the monthly payment in dollars, P is the starting loan principal in dollars, r is the monthly interest rate as a decimal (APR ÷ 1,200), and n is the total number of monthly payments (term in years × 12). The calculator uses the rounded payment to calculate totals.

Total interest is I = M × n − P, and total payments are T = M × n. The balance after one payment is B₁ = P(1 + r) − M. For later months, the balance after k payments is Bₖ = P(1 + r)^k − M × [(1 + r)^k − 1] ÷ r, where k is the number of payments made.

Worked Example

Using the calculator’s defaults: principal P = $200,000, APR = 6.5%, and term = 30 years.

1. Convert the APR to a monthly decimal rate: r = 6.5 ÷ 1,200 = 0.0054166667.
2. Find the number of payments: n = 30 × 12 = 360.
3. Apply the payment formula: M = 200,000 × 0.0054166667 ÷ [1 − (1.0054166667)⁻³⁶⁰] = $1,264.14 per month, rounded to cents.
4. Calculate total payments using that rounded amount: $1,264.14 × 360 = $455,090.40.
5. Subtract principal for estimated total interest: $455,090.40 − $200,000 = $255,090.40.
6. After the first payment, interest is $200,000 × 0.0054166667 = $1,083.33; the remainder reduces principal, leaving a balance of $199,819.19.

Assumptions

• The interest rate remains fixed for the full term.
• Payments are made monthly at the end of each period, with the first payment one month after the loan begins.
• Interest compounds monthly using APR divided by 12.
• Fees, taxes, insurance, PMI, escrow, and any additional or missed payments are not included.

Reading a 30-Year Amortization Schedule

An amortization schedule is a month-by-month record of the payment, interest charged, principal repaid, and remaining balance. At the start of each period, interest is calculated on the outstanding balance. The payment covers that interest first; what remains lowers principal. As principal declines, the interest portion generally declines too, while the principal portion rises, assuming a fixed rate and unchanged payment.

The calculator gives summary figures and the balance after the first payment rather than printing all 360 rows. To build any row, multiply the previous month’s balance by the monthly rate for that period’s interest. Subtract that interest from the regular payment to get principal repaid, then subtract principal repaid from the previous balance. Repeat for each month. In the final row, rounding can require a small adjustment to bring the balance to zero.

When to Use the Estimate

Use this calculation to understand the scheduled principal-and-interest payment for a fully amortizing loan with a fixed APR and monthly payments. It can help you inspect how term, principal, or an APR you enter changes the mathematical schedule. The APR is an input, not a current-rate estimate; obtain the rate and loan figures applicable to your situation from the lender’s disclosure.

The displayed payment is not necessarily the full amount due each month. A mortgage bill may also include items such as taxes, insurance, or escrow, while fees may affect the amount borrowed or the cost shown in loan documents. Those amounts are outside this calculator because it has no inputs for them.

Common Calculation Mistakes and Limits

Use the annual APR as a percentage, such as 6.5, not as the decimal 0.065: the formula divides the percentage by 1,200 to obtain the monthly decimal rate. Enter the principal in dollars and the term in years. A 30-year term means 360 monthly payments, not 30 payments.

Rounding matters. This calculator rounds the regular payment to cents and then multiplies that rounded payment by the number of months for its totals. An actual payment schedule may use lender-specific rounding and a slightly adjusted final payment, so totals can differ by a small amount. The model also assumes a fixed rate and regular payments; it does not represent adjustable rates, payment holidays, late payments, prepayments, or a payoff quote.

How to Use This List

Enter the starting principal, the APR stated for the loan, and the term in years. Check that the APR is entered as a percentage and that the term is the full repayment period. Read the monthly payment first, then use total interest and total payments to see the projected cost across the scheduled term. The first-payment balance illustrates how slowly principal can change early in a long schedule; it is not a substitute for a full lender-generated statement.

If you want to examine a different loan scenario, change one input at a time and compare the resulting estimates. Keep all other assumptions consistent. Do not treat the output as an approval, an offer, or a determination of affordability; it is arithmetic based only on the values entered. This result is an estimate, and the lender’s disclosure gives the exact figures.

Frequently Asked Questions

What does “amortization” mean?
It is the gradual repayment of principal and interest through scheduled payments, with the outstanding balance declining over time.

Why does a 30-year loan have 360 payments?
A monthly schedule has 12 payments each year, so 30 × 12 equals 360 payments.

Does the calculator show taxes and insurance?
No. It estimates principal and interest only; taxes, insurance, PMI, escrow, and fees are not inputs.

Why is more of an early payment interest?
Interest for each month is based on the balance at that time. Since the starting balance is largest at the beginning, the interest charge is typically larger then.

Can I use this for a variable-rate loan?
Not as a complete schedule. The formula assumes one unchanged APR for the entire term, while a variable rate can change the payment or repayment path.

Will the lender’s total match this result exactly?
Not always; fees, payment dates, rounding, and contract-specific details can change the figures. Check the lender’s disclosure for exact amounts.

Final Thoughts

A 30-year amortization schedule shows how a fixed monthly payment is divided between interest and principal over time. Use the estimate to understand the mechanics, and compare it with the lender’s disclosed schedule for the actual loan terms.

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in p | Loan amount | $ | 200000 | 1 | 100000000
in apr | Interest rate (APR) | % | 6.5 | 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
out tot | Total payments | $ | pmt * yrs * 12 | 2
out bal1 | Balance after 1 payment | $ | p * (1 + apr / 1200) - pmt | 2