Calculate your fixed-rate mortgage payment, total interest, and amortization schedule. Compare 10, 15, 20, 25, and 30-year fixed loan terms instantly.
A fixed-rate mortgage locks in your interest rate for the entire life of the loan, so the principal and interest payment does not change once the loan closes. That predictability is why fixed-rate mortgages remain one of the most common mortgage structures in the United States.
This fixed-rate mortgage calculator lets you enter a loan amount, annual interest rate, and term length to estimate your monthly payment, total interest over the life of the loan, and a year-by-year amortization breakdown. Whether you are comparing a 15-year term against a 30-year term or shopping rates from multiple lenders, the worksheet gives you a consistent way to compare scenarios.
Understanding the math behind a fixed-rate mortgage is straightforward: the standard amortization formula produces the same payment every month for the full term. The mix of interest and principal changes over time, with early payments leaning toward interest and later payments leaning toward principal.
Before committing to a mortgage, it helps to see exactly what you will pay each month and over the full term. This calculator helps you compare scenarios in seconds — change the rate by 0.25% or shorten the term by five years and see the impact on your monthly outlay and lifetime interest cost.
Borrowers, agents, and loan officers use fixed-rate payment calculations to set budgets, compare lender quotes, and evaluate whether a specific term fits the plan.
M = P × [r(1 + r)^n] / [(1 + r)^n − 1] Where: M = fixed monthly payment (principal + interest) P = loan principal (amount borrowed) r = monthly interest rate (annual rate ÷ 12 ÷ 100) n = total number of monthly payments (years × 12) If the interest rate is 0%, the formula simplifies to M = P / n.
Result: $2,023.65/month
A $320,000 fixed-rate loan at 6.50% for 30 years produces a monthly P&I payment of $2,023.65. Over 360 payments you will pay $408,514 in interest, bringing the total cost to $728,514. Switching to a 15-year term at the same rate raises the payment to $2,788.35 but cuts total interest to $181,903 — a savings of $226,611.
Every fixed monthly payment contains two portions: interest on the current balance and principal reduction. In the first year of a 30-year, $320,000 loan at 6.5%, roughly $20,600 of your payments goes to interest and only $3,680 to principal. By year 15 the split is nearly even, and in the final year almost every dollar goes to principal. This gradual shift is called the amortization curve.
A fixed-rate mortgage offers predictable payments for the life of the loan, which simplifies long-term budgeting. An adjustable-rate mortgage (ARM) starts with a lower teaser rate that resets periodically — typically after 5 or 7 years. If you expect to sell before the first adjustment, an ARM could save money; otherwise the fixed rate provides insurance against rising rates.
A 15-year fixed mortgage often carries a rate 0.5–0.75% lower than a 30-year and saves more than half the total interest. The trade-off is higher monthly payments. Many financial advisors suggest choosing the 15-year if the payment is no more than 25% of your gross income, and using a 30-year if you need cash-flow flexibility.
Last updated:
This worksheet applies the standard fixed-rate mortgage amortization formula to compute the level principal-and-interest payment from the loan amount, interest rate, and term. It then derives total interest and a year-by-year breakdown from that fixed payment.
The output is for home-financing planning and scenario comparison, not a lender quote, appraisal, or underwriting decision.
A fixed-rate mortgage means the interest rate stays the same for the entire loan term — whether that is 10, 15, 20, or 30 years. Your monthly principal and interest payment is set at closing and never changes, regardless of market rate movements.
A 15-year term has higher monthly payments but a lower interest rate and dramatically less total interest — often less than half. A 30-year term offers lower monthly payments and more cash-flow flexibility. Choose based on your budget and financial goals.
The standard amortization formula multiplies the principal by a factor that accounts for the monthly interest rate and total number of payments. The result is a level payment that covers interest on the declining balance plus a portion of principal each month.
Interest is charged on the outstanding balance. In the beginning the balance is at its highest, so most of each payment covers interest. As the balance decreases, more of each payment goes toward principal. This is called amortization.
Yes. Most conventional fixed-rate mortgages allow prepayment without penalty. Making extra payments reduces your principal faster, which decreases total interest and shortens the payoff timeline.
No. This calculator shows only principal and interest (P&I). Your full monthly housing cost (PITI) also includes property taxes, homeowners insurance, and possibly PMI. Budget an additional 20-40% above P&I for these items.
Rates vary with market conditions, your credit score, and down payment size. As of early 2026, average 30-year fixed rates hover around 6-7%. Excellent credit and a 20% down payment typically secure the best available rate.
Choose a fixed rate if you plan to stay in the home long-term and want payment certainty. An adjustable rate (ARM) can offer a lower initial rate, making it attractive if you plan to sell or refinance within the introductory period.