30 Year Home Loan Amortization Schedule Calculator

This calculator estimates the monthly principal-and-interest payment and total interest for a 30-year home loan, then explains how an amortization schedule tracks the balance over time. Enter the loan amount and annual APR to see the level-payment estimate; the schedule examples show how each payment is divided between interest and principal.

Formula

The fixed monthly payment is calculated with M = round(P × r ÷ [1 − (1 + r)⁻ⁿ], 2). Here, M is the monthly principal-and-interest payment in dollars, P is the original loan amount in dollars, r is the monthly interest rate as a decimal (APR ÷ 1,200), and n is the number of monthly payments (years × 12). The calculator rounds the payment to the nearest cent, then uses that rounded amount to calculate total payments and interest.

Total paid is M × n, and estimated total interest is (M × n) − P. For a monthly schedule, interest in a given month is the opening balance multiplied by r; principal paid is M minus that interest. The closing balance is the opening balance minus principal paid.

Worked Example

Using the calculator’s defaults: P = $300,000, APR = 6.5%, and term = 30 years.

1. Convert APR to a monthly decimal: r = 6.5 ÷ 1,200 = 0.0054166667.
2. Find the number of payments: n = 30 × 12 = 360.
3. Apply the payment formula: M = round($300,000 × 0.0054166667 ÷ [1 − (1.0054166667)⁻³⁶⁰], 2) = $1,896.20 per month.
4. Total scheduled payments: $1,896.20 × 360 = $682,632.00.
5. Estimated total interest: $682,632.00 − $300,000 = $382,632.00.

Assumptions

• The interest rate stays fixed for the full term.
• Payments are made monthly at the end of each payment period.
• Interest compounds monthly using APR divided by 12.
• The estimate excludes fees, taxes, homeowners insurance, PMI, escrow, and any other charges not entered as inputs.

What a 30-Year Amortization Schedule Shows

An amortization schedule is a month-by-month record of the payment, interest, principal, and remaining balance. At the beginning of a fully amortizing fixed-rate loan, the balance is relatively high, so the interest portion is larger. As principal is repaid, the balance falls and less interest accrues each month; with the same payment, more of it goes toward principal.

For the example, the first month’s interest is approximately $300,000 × 0.0054166667 = $1,625.00. The $1,896.20 payment therefore reduces principal by about $271.20, leaving a balance near $299,728.80. Small discrepancies in a displayed schedule can occur because individual lines are rounded to cents.

A 30-year term means 360 scheduled monthly payments, not that each payment is identical across all housing costs. This calculator estimates principal and interest only. A mortgage statement may include escrow or other amounts, and those amounts can change independently. The actual first payment date, payment processing, and loan terms also affect a lender’s detailed figures.

How to Read and Use the Estimate

Enter the principal amount being borrowed, not the home’s price unless the full price is financed. Enter APR as a percent per year: for example, type 6.5 for 6.5%, not 0.065. Use the term in years. The headline result is the estimated monthly principal-and-interest payment; the next outputs show total interest and total scheduled payments over the selected term.

To understand a particular schedule row, multiply that month’s opening balance by the monthly rate to estimate interest. Subtract that interest from the payment to get principal repaid, then subtract principal from the opening balance to get the new balance. The last row may need a small adjustment in real servicing records to bring the balance to zero because payments and interest are rounded or handled according to the contract.

Common Mistakes and Limits

• Confusing APR units: APR is entered as a yearly percentage, while the formula uses APR divided by 1,200 as a monthly decimal.
• Using the purchase price as the loan amount: enter the actual amount financed; a down payment or other financing changes the principal.
• Assuming the payment is the full housing cost: taxes, insurance, mortgage insurance, escrow, and fees are not included.
• Ignoring rounding: the formula rounds the monthly payment to cents before multiplying by the number of payments, so totals can differ slightly from calculations that retain unrounded precision.
• Applying it to a changing rate or unusual payment plan: the standard formula assumes one fixed rate and equal monthly payments, not an adjustable rate, interest-only period, skipped payment, or extra-principal plan.

This is estimate arithmetic for education, not financial advice; the lender’s disclosure gives the exact figures.

Frequently Asked Questions

Does a 30-year home loan always have 360 payments?
A 30-year term has 360 monthly periods under this standard schedule, assuming payments occur monthly and the loan is repaid as planned.

Why does the interest portion shrink over time?
Monthly interest is calculated on the remaining principal, so it generally declines as the balance is paid down at a fixed rate.

Does this calculator include property taxes or homeowners insurance?
No. It estimates principal and interest only; enter or review those other costs separately using figures supplied for the property and loan.

Can I use it for a variable-rate mortgage?
It can illustrate a single-rate period, but it does not project later rate changes or recalculate payments after a rate adjustment.

Why might my lender’s payment differ by a few cents?
Lenders may use different rounding, payment dates, daily-interest conventions, or contract-specific calculations, and the quoted APR or financed amount may differ from your inputs.

Final Thoughts

A 30-year amortization schedule makes the relationship between payment, interest, principal, and outstanding balance easier to see. Treat the calculator as a transparent estimate, check that the inputs match the loan terms, and use the lender’s disclosure for the exact payment and schedule.

Related

• Loan Term Sheet: Meaning, Terms, and How to Review
• Loan Term Out Calculator: Estimate Months to Payoff
• Loan Term Options and Monthly Payment Calculator

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 term | $ | pmt * yrs * 12 - p | 2
out tot | Total principal and interest | $ | pmt * yrs * 12 | 2