Mortgage Amortization Calculator

This mortgage amortization calculator is the schedule-focused sibling in the mortgage group. Instead of asking only “What is my payment?” it asks “What will be left after a specific payment, and how much of that payment goes to principal versus interest?” That makes it useful for homeowners planning a refinance, buyers comparing 15-year and 30-year terms, and anyone trying to understand why early mortgage payments build equity slowly.

For a basic payment without schedule detail, use the simple mortgage calculator. For the main home-price payment with taxes, insurance, HOA dues, PMI, and optional extra payments, use the mortgage calculator. For a PITI and escrow view, use the mortgage calculator with taxes and insurance. For rate and fee comparisons, use the mortgage rate calculator.

What the calculator reports

Enter the loan amount, annual interest rate, loan term, and payment number to inspect. The calculator first computes the fixed monthly principal-and-interest payment. It then loops month by month up to the inspected payment. During each loop, interest equals the current balance times the monthly rate. Principal equals the fixed payment minus that month’s interest. The balance falls by the principal amount.

The output shows the balance after the inspected payment, the full monthly principal-and-interest payment, principal in that specific payment, interest in that specific payment, remaining balance, cumulative principal repaid, cumulative interest paid, the share of the loan repaid, total interest over the term, and total principal and interest. It does not include tax, insurance, PMI, HOA dues, or escrow.

Calculation

For original loan principal P, monthly interest rate r, and n monthly payments, the standard amortized-payment formula is:

$\text{M} = P \frac{r(1+r)^n}{(1+r)^n-1}$

For each month in the schedule:

$\text{interest for month} = \text{previous balance} \cdot r$

$\text{principal for month} = \text{M} - \text{interest for month}$

$\text{new balance} = \text{previous balance} - \text{principal for month}$

If the interest rate is zero, the calculator sets interest to zero and divides principal evenly across the scheduled months.

Checking a mortgage amortization scenario

The default loan amount is 300,000 dollars, the interest rate is 6.5 percent, the term is 30 years, and the payment number to inspect is 60. The term creates 360 scheduled payments. The monthly rate is 0.065 divided by 12, or about 0.0054167.

The fixed principal-and-interest payment is 1,896.20 dollars. After looping through 60 payments, the remaining balance is 280,832.93 dollars. Payment 60 itself contains 1,523.20 dollars of interest and 373.01 dollars of principal. Across the first 60 payments, cumulative principal repaid is 19,167.07 dollars and cumulative interest paid is 94,605.18 dollars. That means only about 6.39 percent of the original loan has been repaid after five years, even though 113,772.25 dollars of scheduled payments have been made.

Over the full 30-year schedule, total principal and interest is 682,633.47 dollars, and total interest is 382,633.47 dollars. The example highlights the central fact of amortization: early payments are dominated by interest because the balance is still high.

Why amortization feels slow at first

A fixed-rate mortgage payment is level, but the balance is not. In month one of the default example, interest is based on nearly the entire 300,000 dollar balance. The fixed payment must cover that interest first, so only the remainder reduces principal. By month 300, the balance is far smaller, so the interest charge is lower and more of the same payment goes toward principal.

This is why refinancing can reset the clock. If you replace an old loan with a new 30-year loan, the new schedule starts over from the new principal, rate, and term. The payment may fall, but you may also extend the time over which interest accrues. The calculator does not model refinance closing costs or cash-out proceeds; it simply shows the schedule implied by the numbers entered.

PITI, escrow, and rate context

Amortization is only the loan payoff story. A real monthly housing payment may also include PITI: principal, interest, taxes, and insurance. Taxes and insurance may be collected through escrow, and PMI or HOA dues may be added to monthly cash flow. Those amounts can make the monthly payment much higher, but they do not reduce the balance shown here.

Rates matter because a higher rate increases the interest charge in every early month. To isolate rate sensitivity, compare the same loan in the mortgage rate calculator. To estimate cash needed before the loan starts, use the down payment calculator. To see whether the payment fits income, use the debt-to-income calculator. This page is informational only and does not replace a lender’s amortization schedule or financial advice.

Method scope and source version

Jurisdiction-neutral loan mathematics; lender contracts, disclosures, taxes, insurance, PMI, and compounding conventions vary. Evergreen method only; defaults/examples must not be represented as current market, legal, tax, or institutional data. The sources below support the stated method and definitions; they do not supply a live rate, quote, legal conclusion, lender offer, or institution-specific policy.

Sources

• Consumer Financial Protection Bureau, Loan Estimate explainer — projected payments and loan-cost context.
• Consumer Financial Protection Bureau, Explore interest rates — rate and borrower-factor context.
• Freddie Mac, Primary Mortgage Market Survey — mortgage-rate market reference.
• Federal Reserve, Selected Interest Rates H.15 — broader interest-rate data context.