Home Loan Amortization Schedule: Monthly Payment and Balance

A monthly home loan amortization schedule shows how each payment is divided between interest and principal, and how the balance changes over time. Enter the loan amount, annual interest rate, and term to calculate the estimated monthly principal-and-interest payment and total interest; the schedule itself can then be built month by month from those figures.

Formula

The calculator uses the standard fixed-payment loan formula. It calculates the monthly payment from the starting principal, monthly interest rate, and number of monthly payments:

Payment = P × r ÷ [1 − (1 + r)⁻ⁿ]

• P is the loan principal, in dollars.
• r is the monthly interest rate as a decimal, calculated as APR ÷ 1,200. For an 8% APR, r is 0.08 ÷ 12.
• n is the number of monthly payments, calculated as the term in years × 12.

Total interest is calculated as the monthly payment multiplied by the number of payments, minus the original principal: Total interest = payment × n − P. This is an estimate using the unrounded formula payment for the displayed payment and interest outputs; actual loan servicing applies payment and rounding rules stated in the loan documents.

Worked Example

Using the calculator’s defaults—$20,000 principal, 8% annual rate, and a five-year term—the monthly rate is 0.08 ÷ 12 = 0.0066667, and the term is 5 × 12 = 60 payments.

1. Substitute into the payment formula: $20,000 × 0.0066667 ÷ [1 − (1.0066667)⁻⁶⁰].
2. The resulting monthly principal-and-interest payment is approximately $405.53.
3. Total interest is approximately $405.53 × 60 − $20,000 = $4,331.80.

Displayed amounts are rounded to cents. The formula block calculates the total using the unrounded payment, so a small difference from multiplying the displayed rounded payment by 60 can occur.

Assumptions

• The rate stays fixed for the full term.
• Payments are equal, made monthly, and applied at regular intervals.
• Interest is calculated monthly using APR divided by 12.
• The estimate excludes fees, taxes, homeowners insurance, mortgage insurance, and escrow. It also assumes no extra payments, missed payments, or changes to the loan.

How a Monthly Amortization Schedule Works

At the start of each period, interest is calculated on the outstanding principal. The payment covers that period’s interest first; the remainder reduces principal. As principal falls, the next month’s interest charge generally falls too. With a fixed rate and level payments, more of each payment therefore goes toward principal later in the schedule.

A schedule typically lists the payment number or date, beginning balance, payment, interest, principal reduction, and ending balance. The basic calculations for each month are:

• Monthly interest = beginning balance × monthly rate.
• Principal paid = payment − monthly interest.
• Ending balance = beginning balance − principal paid.

For example, at the default rate, the first month’s interest on $20,000 is about $133.33. From a $405.53 payment, roughly $272.20 reduces principal, leaving a balance near $19,727.80. Later, interest is computed on that lower balance. A full schedule repeats the calculations, with small cent-level adjustments possible in the final payment.

What the Calculator Does and Does Not Show

This calculator gives the level monthly principal-and-interest payment and an estimated total interest amount for a fixed-rate loan. It does not produce every dated row of a full schedule, but those rows can be derived using the monthly steps above. A lender’s payment amount may differ if the loan uses a different rate structure, payment timing, day-count method, rounding convention, or other contract terms.

A home loan’s total housing payment can include items beyond principal and interest. Property-related charges, insurance, mortgage insurance, and escrow collections are not part of the formula because they are not inputs here. Ask the lender for the payment breakdown and use the figures in the loan disclosure when checking an actual loan.

Reading the Results and Avoiding Common Errors

The monthly payment is not the same as the total cost of owning a home or even the complete monthly amount due to a loan servicer. Total interest is also not a separate monthly bill: it is the estimated sum of interest over the entire modeled term if every scheduled payment is made as assumed.

• Enter APR as a percentage, such as 6.5, not as the decimal 0.065.
• Use the amount actually borrowed as the principal, not the home’s purchase price if the down payment is not financed.
• Check the term units: the input is years, and the formula converts years to months.
• Do not assume extra principal payments are included. They change the balance path and usually reduce interest compared with this no-extra-payment schedule.
• Do not interpret a rounded display as a guaranteed payment quote. Servicing calculations can vary by contract and rounding method.

For an adjustable-rate loan, a single fixed-rate schedule cannot represent future payment changes. A schedule based on the initial rate is only a snapshot under that rate assumption, not a prediction of later payments.

Frequently Asked Questions

What is a monthly home loan amortization schedule?
It is a month-by-month record showing how each scheduled payment is divided between interest and principal, along with the remaining balance.

Does a mortgage payment stay the same every month?
The principal-and-interest portion stays level under the fixed-rate assumptions used here. The full amount due can differ when taxes, insurance, escrow, or other charges change.

Why does the first payment go mostly to interest?
Interest for the period is calculated on the starting balance. Early in repayment that balance is largest, so the interest share is relatively high; as principal declines, the interest share generally shrinks.

Does this estimate include property taxes and insurance?
No. The calculator estimates principal and interest only. Taxes, insurance, mortgage insurance, and escrow are excluded.

Can extra monthly payments change the schedule?
Yes. An extra amount applied to principal lowers the balance faster than the standard schedule assumes, which changes later interest and payoff timing. This calculator does not model extra payments.

The result is an estimate, and the lender’s disclosure gives the exact figures.

Related

• Home Equity Loan Calculator: Amount Up to a CLTV Limit and Payment
• Mortgage Calculator With Escrow: Payment With Tax and Insurance
• Mortgage Loan Amount Calculator: The Loan a Monthly Payment Repays

in p | Loan amount | $ | 20000 | 1 | 100000000
in apr | Interest rate (APR) | % | 8 | 0.01 | 100
in yrs | Loan term | years | 5 | 0.0833 | 50
out pmt | Monthly payment | $ | p * (apr / 1200) / (1 - (1 + apr / 1200) ^ -(yrs * 12)) | 2
out int | Total interest | $ | pmt * yrs * 12 - p | 2