Monthly Mortgage Calculator

A 1% difference in mortgage rate can add over $100 to your monthly payment on a $300,000 loan. Whether you’re buying your first home or refinancing, knowing your exact monthly obligation helps you budget and compare offers. The monthly mortgage calculator above lets you instantly see how loan amount, interest rate, and term shape your payment–so you can make a confident decision.

This tool provides estimates for educational purposes only; consult a financial advisor for personalized advice.

How to Calculate Your Monthly Mortgage Payment

Most U.S. mortgages use a standard annuity formula to spread principal and interest evenly over the loan term. The calculator above applies this same math. You enter three core inputs:

• Loan amount – the total you borrow after your down payment.
• Annual interest rate – the yearly cost of borrowing, expressed as a percentage.
• Loan term – the number of years you have to repay (commonly 15 or 30 years).

With these, the calculator computes the monthly payment that fully repays the loan by the end of the term. It also shows total interest paid and the amortization schedule.

Breaking Down the Mortgage Payment Formula

The classical monthly mortgage payment formula for a fixed-rate loan is:

Where:

• M = monthly payment
• P = principal (original loan amount)
• r = monthly interest rate (annual rate divided by 12)
• n = total number of payments (loan term in years × 12)

For example, a $300,000 loan at 6.5% for 30 years works out as:

• r = 0.065 / 12 = 0.0054167
• n = 30 × 12 = 360
• M = 300,000 × (0.0054167 × (1.0054167)^360) / ((1.0054167)^360 – 1) ≈ $1,896

The monthly mortgage calculator automates this computation, including optional extras such as taxes and insurance.

Principal vs. Interest Over the Loan Term

In the early years, the majority of each payment covers interest; a smaller portion reduces principal. Over time the balance shifts. With the example above:

• Month 1: interest = $1,625, principal = $271. The remaining balance falls to $299,729.
• Year 10: interest ≈ $1,370, principal ≈ $526.
• Year 25: interest ≈ $520, principal ≈ $1,376.

An amortization table – which the calculator can display – breaks down every payment. This helps you see how extra principal payments can shorten the term and save thousands in interest.

What Else Is Included in Your Monthly Payment?

Your monthly housing cost often goes beyond principal and interest. The calculator allows you to add:

1. Property taxes – typically assessed annually by your county and prorated monthly. For a $400,000 home with a 1.2% tax rate, that’s $4,800 per year, or $400/month.
2. Homeowners insurance – required by lenders; average U.S. premium is around $1,700 per year, or about $142/month.
3. Private mortgage insurance (PMI) – mandatory for conventional loans with less than 20% down. PMI often costs 0.5% to 1.5% of the original loan amount per year. On a $285,000 loan (after 5% down), 1% PMI adds $237/month.
4. HOA dues – if the property is in a homeowners association, monthly fees can range from $100 to $500 or more.

Lenders commonly bundle taxes and insurance into an escrow account, meaning your total payment to the servicer includes those amounts. When comparing mortgage offers, always look at the full PITI (Principal, Interest, Taxes, Insurance) figure.

Real-Life Calculation Example

Assume you’re buying a home priced at $400,000. You put 15% down ($60,000) and finance $340,000 on a 30-year fixed-rate mortgage at 6.75%. Annual property taxes are 1.1%, and insurance costs $1,800 per year. You’ll also pay PMI because your down payment is below 20% – say 0.7% of the loan annually.

Using the monthly mortgage calculator:

• Principal & interest: $2,206
• Taxes: $367
• Insurance: $150
• PMI: $198
• Total estimated monthly payment: $2,921

Over 30 years you would pay roughly $454,000 in interest alone. Adding just $200 to principal each month could shave off over 5 years and save more than $80,000 in interest.

Key Factors That Affect Your Monthly Mortgage Payment

Even small changes in loan parameters can significantly impact your payment:

• Interest rate: On a $350,000, 30-year loan, the difference between 6.5% and 7.0% is about $119 extra per month – or $42,840 over the life of the loan.
• Loan term: A 15-year term forces higher monthly payments but drastically reduces total interest. For the same $350,000 at 6.5%, the 15-year payment is $3,049 vs. $2,212 for 30 years, but interest saved exceeds $180,000.
• Down payment: A 20% down payment eliminates PMI and often qualifies you for better rates. On a $300,000 purchase, putting 20% down vs. 5% down reduces the loan amount from $285,000 to $240,000, shrinking the monthly principal and interest by roughly $350–$400.
• Credit score: Borrowers with scores above 740 typically get the most favorable rates. According to the Consumer Financial Protection Bureau, even a one-tier drop in credit score can raise the rate by 0.25%–0.5%.
• Loan type: Government-backed loans (FHA, VA, USDA) may offer lower down payments or no PMI, but they can carry upfront funding fees or higher mortgage insurance premiums.

Use the calculator to test various scenarios – adjusting one factor at a time shows you exactly where you can save. For a complete picture of current rate assumptions, visit Fannie Mae’s economic and housing outlook or your national housing finance agency.